edexcel chemistry - unit1 as

8/13/2019 Edexcel Chemistry - Unit1 AS

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Sub-atomic

particle

Relative

charge

Relative

mass

Mass No E(element)Atomic No

E = hf Energy = Plancks constant x freuencyAtomic number Proton number

Mass number Proton number plus the number of neutrons in thenucleus of its atom

Proton

Electron

!eutron

"#

-#

$

#

negligible

#

Hydration %hemical combination of &ater an' another substance

Solvent Substance in &hich other substances are 'issolve'Solute Substance 'issolve' in another substance(solvent)to form a solution

Empirical formula Ratio of atoms of 'ifferent elements present in a molecule of a compoun' in their lo&est terms as &hole numbers(%* has %* empirical formula)

Molecular formula +ctual number of atoms of each element in a molecule of a compoun'

Dibasic acid ,ne &hich has replaceable * atoms per moleculeIsotopes +toms having the same atomic number but 'ifferent mass numbers

- +s the number of protons increases the number of neutrons increases relatively faster so small atoms have proton an' neutron

numbers &hich are comparable &hereas large atoms have more neutrons than protons

- !eutrons re'uce repulsive forces bet&een positive protons

- .eparture from optimum range of ratio of protons to neutrons &ill lea' to nuclear instability(ra'ioactivity)- !o of electrons in outer(valence)shell(an' sometimes the shell next to the outer shell)an' the /Es 0 E+s for an atom &ill

'etermine the chemistry of the element

- ,uter shell electrons 'etermine the chemistry of an element as they can get close to the outer shell electrons of other atoms so can

be transferre' or share'1 2he inner shell electrons are tightly hel' an' shiel'e' from the electrons in other atoms3molecules

- /sotopes 'ont affect the electron number or structure so 'ont affect the chemistry of the element but have varying rates of reaction

- #% is the only atom &ith relative atomic mass &hich is an exact &hole number because #% is chosen as a stan'ar' an' given a

relative atomic mass of exactly #

Nuclide + nuclear species of given mass number an' atomic number Radionuclide Ra'ioactive nucli'eRelative atomic massAverage mass of an atomof an element compare' &ith #3# of the mass of an atom of carbon-# isotope

Relative isotopic massMass of an atom of an isotopeof an element compare' &ith #3# of the mass of an atom of carbon-# isotopeRelative molecular mass Sum of relative atomic masses

# Electrons are emitte' from the filament accelerate' an' use' to bombar' thegaseous sample &hich is at very lo& pressure

Sample molecules have electrons knocke' off them by bombar'ing electrons

forming positive ions1 2he molecules can also fragment or rearrange giving 'ifferen

positive ions

4 Positive ions accelerate' by an electric fiel'

Positive ions 'eflecte' by a magnetic fiel' in a circular path &hose ra'ius 'epen'

on mass3charge ratio an' strength of the fiel'1 2he machine s&eeps over the chosen

mass range by altering the magnetic fiel' an' hence ions reaching the 'etector areseparate' accor'ing to their mass

5 Positive ions(Species6 ra'ical cation3molecular ion3fragment ion) 'etecte' an'relative amounts calculate' by the machine

- %hamber vacuume' to prevent air molecules obstructing the passage of particles through the mass spectrometer- 7ikelihoo' of "ions being pro'uce' in the mass spectrometer is small because the chance of a molecule being ionise' by electron

impact is alrea'y uite small1 8hen it has been ionise' it is pulle' a&ay by the potential gra'ient lea'ing to the magnet &hich also he

to re'uce the possibility of a secon' impact

- /mportant to use minimum possible energy to ionise a sample in a mass spectrometer to prevent formation of 'ouble positive ions ra

than single positive ions(or to prevent fragmentation of molecular substances)

(Abundance ! Mass" # (Abundance ! Mass" #$%%

&otal composition = Relative atomic mass RAM

Molecular ion pea' (2he molecular ion peak is not al&ays the most intense an' maybe absent)

*ighest significant peak &here the molecule has lost # electron but has not broken up

ase pea' *ighest peak in the mass spectrum

- /f the sample is an element each line represents an isotope of the element- 9olecules broken up into fragments make fragmentation patterns on the mass spectrum(use' to i'entify molecules an' structure)

- Relative masses are :ust numbers no units

- !o element in the perio'ic table has a relative atomic mass that is a &hole number because relative atomic mass is an average so its

not usually a &hole number

- 9ass spectrometer &ith gas-liui' chromatography use' in forensic &ork for analysis of complex mixtures samples intro'uce' to g

liui' chromatograph an' various constituents separate' output gases then le' to mass spectrometer fragmentation patterns compare'

&ith large 'atabase of patterns from kno&n substances

- ,nce the electron has passe' the final ano'e it 'oesnt 'ecelerate an' go back to the ano'e because it has either colli'e' &ith a gase

molecule or passe' on to earth(groun')at the other en' of the chamber- /t is a goo' approx to consi'er that relative atomic mass of ;7i"'etermine' in a mass spectrometer is the same as that of ;7i because

mass of the electron lost from ;7i to form ;7i"is negligible

(#) %alculate R+9 from these isotopes an' their < compositions 5e 51>


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51> " ?#1; " 1 " $144 = 551?#('p)

)stIonisation ener*y M(*" M#(*" # e+

Energy3enthalpy change per mole to remove an electron from each atom in the gas phase to form a singly positive ion

,ndIonisation ener*y Energy3enthalpy change per mole for the process M#(*" M,#(*" # e+

)stElectron affinity -(*" # e+ -+(*"

Energy3enthalpy change per mole for each atom in the gas phase to gain an electron to form a singly negative ion- !egative(exothermic) since the electron is attracte' by the positive charge on the atoms nucleus

,ndElectron affinity Energy3enthalpy change per mole for the process -+(*" # e+ -,+(*"

- Positive(en'othermic) since energy nee'e' to overcome repulsion bet&een the electron an' negative ions

Ener*y level Electrons in atoms can only have certain amounts of energy groups of electrons can exist &ith roughly the same amoun

energy these positions of roughly similar amounts of energy are calle' energy levels

SiAe of /E 'epen's on B Nuclear char*e B Atomic radius B Electron shieldin*. ener*y level

Successive IE/s increasebecause electrons are being remove' from increasingly positive ions an' so the attractive forces are greater

- 7arge :umps in /Es arise from a large increase in attraction correspon'ing to an electron being remove' from a ne& energy level

significantly closer to the nucleus(proving that electrons are arrange' in shells)IE/s increase across periods(left to right)

B !umber of protons increasing meaning stronger nuclear attraction

B Extra electrons are at roughly the same energy level even if the outer electrons are in 'ifferent orbital types

B 7ittle extra shiel'ing effect little extra 'istance to lessen the attraction from the nucleusIE/s decrease do0n *roups B Each element 'o&n a group has an extra electron shell

B Extra inner shells means extra 'istance of outer electrons from the nucleus an' greater shiel'ing from the attraction of the nucleus

overall re'ucing nuclear attraction

Atomic radius decreases across period 1(left to right) !uclear charge increases electrons pulle' closer to the nucleus electrons are aa''e' to the same outer shell

2rincipal 3uantum number(n" shell numbers Subshell #stshell has no subshell 4rbital s subshell has # orbital p has 4 ' has 5

5Aufbau/ 5build up/ principleB Electrons are a''e' to the lo&est energy orbital available

B ,ne at a time B 8ith no more than electrons occupying one orbitalB /f there are several orbitals of the same energy available then electrons enter

these orbitals singly so as to be as far apart as possible

B *alogens have high /Es so they 'ont form positive ions but negative ions

because they have one electron less than a full shell

B +nomalously lo& E+ for 'ue to repulsion of the incoming electron from a

concentrate' electric fiel' of a small atom

6uantum mechanics 2he electron in an atom behaves as a &ave &hich is a mathematical construction not a particleAtomic orbital /S the electron3pair of electrons the volume in &hich the electron has a ?5< probability of being foun'(no such thing

an empty orbital)Spin is a property of an electron1 2he electrons in an orbital have opposite spins helping to counteract the repulsion bet&een their

negative charges(spin pairing)

n SubshellNumber of electrons Subshell #s s p 4s 4p 4' s p ' f

9ax number of electrons ; ; #$ ; #$ #


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C Symbol #s s p 4s 4p 4' s p

# * #

*e

4 7i #

De

5 D #

; %

@ ! 4

> ,

? 5

#$ !e ;## !a ; #

# 9g ;

#4 +l ; #

# Si ;

#5 P ; 4

#; S ;

#@ %l ; 5

#> +r ; ;

#? ; ; #

$ %a ; ;

# Sc ; ; #

2i ; ;

4 F ; ; 4

%r ; ; 5 #

5 9n ; ; 5

; e ; ; ;

@ %o ; ; @

> !i ; ; >

? %u ; ; #$ #

4$ Cn ; ; #$

4# Ga ; ; #$ #

4 Ge ; ; #$

44 +s ; ; #$ 4

4 E ; ; #$

45 Dr ; ; #$ 54; r ; ; #$ ;

Group // De #ss #st/E = ?$$ kHmolI#

Group /// D #sspx#

#st/E = @?? kHmolI#

Group F ! #sspx#py

#pA#

#st/E = #$$ kHmolI

Group F/ , #sspxpy

#pA#

#st/E = #4#$ kHmolI

! s p , s p

B /n D the p electron easier to remove than the s electron from

De because subshells that are full are more stable

B /n D the p orbital is further from the nucleus

B 2he p orbital is screenednot only by the #s electrons but alsopartially by the s electrons

- 2hese factors are strong enough to overri'e the effect of the

increase' nuclear charge resulting in the /E to 'rop slightly

B Screenin* identicalan' electron being remove' is from ani'entical orbital

B ! structure is symmetricalan' more stable than that in ,

B Repulsion bet0een , electrons in the same orbitalmeans an

electron in the pxpair is easier to remove

() +n atom contains 5 protons an' 5 neutrons give the symbol fo

this atom inclu'ing the mass number (a) D() ormula of the compoun' forme' bet&een this element an'

chlorine (a) D%l4

(#)(i)9ass spectrum of *%l peak at mass 4; is molecular ion (* 45%l)" %hlorine has only

isotopes 45%l 4@%l 8hat particle is responsible for peak mass 4>J (#)(i) (* 4@%l)"

(ii)*o& 'o you explain the fact that the height of the peaks at mass 4; is 4 times as high than the

peak at mass 4>

(ii)2here is 4 times as much 45%l to 4@%l an' therefore 4 times as much *45%l to *4@%l

()(a)9ass spectrum of methane peak at mass #; is molecular ion(%*)"

Explain peaks of relative mass # # #4 # #5 #@

Relative mass # # #4 # #5 #@

(#*)" (*)" (#%)" (#%#*)" (#%#*)" (#%#*4)

" (#%#*4*)"

()(a)Dromine consists of isotopes mass numbers @? an' >#1 + sample of Dr(g) &as examine' in a mass spectrometer1 /'entify

the species responsible for the peak at m/e= #;$ ()(@?Dr>#Dr)"

()(b)or a particular sample of copper t&o peaks &ere obtaine' in the mass spectrum

(i)Give the formula of the species responsible for the peak at m/e = 65 (i);5%u"

(ii)State &hy t&o peaks at m/e values of ;4 an' ;5&ere obtaine' in the mass spectrum

(ii) 'ifferent isotopes

(4)*o& &oul' accelerating fiel' an' magnetic fiel' 'iffer in its affect on K"an' K" J

(4)2he accelerating force an' 'eflecting fiel' on K" &ill be t&ice that on K"

() reasons &hy particles must be ionise' before being analyse' in a mass spectrometerJ ()*ave to be accelerate' then 'eflecte'

(5)Doron relative atomic mass #$1> gives peak mass spectrum m3A=#$ an' m3A=## %alculate the ratio of the heights of the peaks

(5)#$x " ##(# I x) = #$1> x = $1 y =# I x = $1> ratio of heights = #6(@)Explain &hy has lo&er #st/E than !a

(@)B Electron being remove' is further from the nucleus B 9ore shiel'ing B Re'uces attraction of the nucleus

Peak at m/e Relative abun'ance

;4 ;?1#

;5 4$1?


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(>)8hat force causes the scattering of L particles by nucleiJ

(>)L particles an' nuclei both positively charge' thus electrostatic forces of repulsion

(?)Explain &hy all isotopes of 9g have the same chemical properties(?)B Same number of electrons in all 9g isotopes B ,uter electron structure

'etermines chemical properties

(#$)Msing subshell notation give electronic configuration of atom an' "ion

(#$) #ssp;4s4p;s# "#ssp;4s4p;

(##)State &hy peaks at m3e values of ;4 an' ;5 &ere obtaine' in a mass spectrum

of an element (##) 'ifferent isotopes

(#)8rite euation for 5thionisation of !a (#)!a"(g)!a5"(g) " eI

(#)2he logarithm of successive /Es for 9g across the page

Explain &hat this graph tells you about the electron arrangement in the 9g atom(#)2&o3big :umps sho& 4 'ifferent shells present. sho&s 1>1

;

5

)

4

-

#

$

$ # - 4 ) 5 ; @ > ? # $ # # #! u m b e r o f e l e c t r o n r e m o v e '

7

o

g

io

n

is

a

tio

n

e

n

e

rg

y

3k

H

m

o

lI

#

in' the empirical formula of the compoun' containing % 1$< * 15?< Dr @414?< by mass

+tomic ratio Simplifie' atomic ratio

% 1$3#= #1>45 #1>453$1?#@ =

* 15?3#= 15? #1>45615?6$1?#@ 15?3$1?#@ = 5

Dr @414?3>$= $1?#@ $1?#@3$1?#@ = # Empirical formula is thus %*5Dr

(#)%ompoun' K contains only D an' * < by mass of D in K is >#1< /n mass spectrum of K the largest value peak of m3A is at 5

%alculate empirical an' molecular formula

(#)D6* = >#13#$1> 6 #>1>3# @15#6#>1> #615 65 Empirical formula is D*5 9r(D*5) = ;1; 9olecular formula = D*#()*y'raAine(empirical formula !*)mass spectrum of this compoun' sho&s a molecular ion peak at m/e4

sho& the molecular formula of hy'raAine is !*

()Relative 9olar 9ass = 4 n(! " *)= 4 n(# " )= 4 n= 9olecular formula = N !*= !*

Euations are6 B /nternationally un'erstoo' B Ouantitative B Shorter than the same information given in &or'sE3uations balance for mass and total char*e7*S 0 R*S have the same number of each type of atom if there are positives on 7*

there must be on R*S

/onic euations6 ) 8rite soluble ionic compoun's &ith the ions separate' , 8rite insoluble ionic an' covalent compoun's as usual

1 %ross out spectator ions(ions &hich appear on both si'es of the euation)

!a%l(a) " +g!,4(a)!a!,4(a) " +g%l(s)

Silver nitrate silver chlori'e(&hite ppt)

Ions: !a"(a) " %lI(a) " +g"(a) " !,4I(a)!a"(a) " !,4

I(a) " +g%l(s)

Deleting spectator ions: +g"(a) " %lI(a)+g%l(s)

9n,(a) " >*S,(a) " #$eS,(a)9nS,(a) " 5e(S,)4(a) " S,(a) " >*,(l)

potassium manganate(F//) iron(//)sulphate

Ions: "(a) " 9n,I(a) " #;*"(a) " #>S,

I(a) " #$e"(a)9n"(a) " #$e4"(a) " #>S,I(a) " "(a) " >*,(l)

Deleting spectator ions:9n,I

(a) " >*"

(a) " 5e"

(a)9n"

(a) " 5e4"

(a) " *,(l)

Avo*adro constant NAis ;1$ x #$4molI#(7 7oschmi'ts number)

- +t R2P ?> #$$kPa # mol of gas occupies 'm4

- Folumes of all gases are eual un'er the same con'itions an' contain the

same number of particles

- # mol of any substance B is ;1$ x#$4particles of it

B is its relative molecular3atomic mass in g(molar mass gmolI#)

- e(s) " S(s)eS(s) %ontain the same number of particles

/n'icator p in' p* range *alf &ay colour

7itmus ;15 5-> .ark purple9ethyl orange 41@ 41#-1 ,range

Phenolphthalein ?14 >14-#$ Pale pink


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&itration73uantitative7volumetric analysis(analysing amount of substance present)

B Folumes of both solutions an' concentration of one of them kno&n

B %omplete reaction bet&een substances means concentration of the other solution can be foun'

2itration proce'ure6 B Rinse out the burette &ith 'istille' &ater follo&e' by a little of the solution to be use' in it

Ensure that any &ater in the burette 'oes not 'ilute the solution if not then the titration &oul' be too lar*e!,2&rongQ

first titration must only be consi'ere' rough

B ill the burette(so theres no air bubbles an'readin* at eye8level 0hereby the bottom of the meniscus is level 0ith the 9ero ma

B 8ash out the conical titration flask &ith 'istille' &ater

B Rinse out the pipette &ith 'istille' &ater follo&e' by a little of the solution to be use' in it

B Mse the pipette to measure out the reuire' volume of solution into the conical flask I +voi'ing air bubbles

I Rea'ing pipette at eye-level &hereby the bottom of the meniscus is level &ith the mark I 2ouching the si'e of the flask &ith the tip of the pipette leaving a 'rop in the tip of the pipette

B +'' # or 'rops of in'icator to the solution in the conical flask1 Place the flask on the &hite tile un'er the burette

B +'' aci' to alkali by s0irlin* the conical flask then drop80iseto&ar's the en' point &hereby the in'icator colour changes by the

a''ition of one 'ropB %arry out a rough titration then accurate titrations &hich agree to 0ithin :%)cm1of each other

B Recor' results as a statement an' table

Molar solution of a substance(mol'mI4 g'mI4),ne mole of a substance has &ater a''e' until the volume of the solution is #'m4

Acid7base titrations(+ci' 0 base reacte' &ith a suitable in'icator)fin's the purity of a substance or pro'uces a stan'ar' solution for uin another titration

Standard solution ,ne &hich can be ma'e of kno&n concentration by &eighing out the primary stan'ar'(solute)

Primary stan'ar'(solute)must6 # De available commercially in a high state of purity

De stable over long perio's of time

4 !ot be volatile(so losses 'ue to evaporation 'uring &eighing 'ont occur) !ot 'ecompose &hen 'issolve' in &ater

5 !ot absorb &ater or %,from the atmosphere

9aking a stan'ar' solution of !a%,4(a)of kno&n concentration6

# #15g of pure anhy'rous !a%,4 is 'issolve' in a beaker &ith 'istille' &ater Msing a funnel an' a glass ro' the solution is transferre' to a 5$cm4gra'uate' flask

4 2he beaker is &ashe' a couple of times &ith 'istille' &ater an' the 0ashin*s are added to the *raduated flas'

9ake the mi!ture up to 5the mar'/ 0ith distilled 0ater

5 Stopper the flas' and sha'e to ensure that the solution is homo*enous

(#)!a%,4(s) " *%l(a)!a%l(a) " *,(l) " %,(g)

#15g of !a%,4in #'m4solution 5cm4of this titrate' &ith *%l 415cm4of *%l &as reuire' concentration of the aci'J

(#)!a%,4= #$;gmolI# #15g'mI43#$;gmolI# = $1##>mol'mI4(concentration)

$1$5'm4x $1##>mol'mI4= $1$$?5mol(+mount of !a%,4) # mol of !a%,4reuires mol *%l

+mount of *%l= $1$$?5mol x= $1$$5?mol $1$$5?mol3$1$45'm4

= $15#mol'mI4

()#g !a%,4 'issolve' in &ater an' volume ma'e to $$cm4

Portions of 5cm4of this solution &ere titrate' &ith $1#mol'mI4*%l solution 8hat volume &as reuire'J

()Folume reuire' 'epen's on in'icator use' assuming methyl orange use' !a%,4" *%l!a%l " *, " %,+mount of !a%,4 = #g3#$;gmol

I# = ?14 x#$I4mol +mount of *%l = x ?14 x#$I4mol = #1>>@ x#$Imol

Folume of *%l reuire' = #1>>@x#$Imol3$1#mol'mI4 = $1#5@'m4

(1"#cm4of (conc)*S,in a 5$$cm4gra'uate' flask ma'e up to the mark &ith pure &ater

5cm4portions titrate' &ith $1#mol'mI4!a,*(a) #?1>cm4of !a,* nee'e'1 %oncentration of original aci'J

(1"*S,(a) " !a,*(a)!aS,(a) " *,(l) +mount of !a,* = $1$#?>'m4x $1#mol'mI4= #1?> x#$I4mol

Since # mol *S,reuires mol !a,* +mount of *S,= #1?> x#$I4mol3 = ?1? x#$Imol

?1? x#$Imol in 5cm4 ?1?x#$Ix 5$$35 $1$#?>mols in #cm4of (conc)*S,#?1>mols in #'m4conc = #?1>mol'mI4

()ac'8titration(concerning substances &hich are insoluble)use' to fin' purity of sample of chalk &hich is insoluble in &ater

+ solution cant be use' so its reacte' &ith a kno&n amount of excess aci' aci' remaining then titrate' &ith stan'ar' alkali

#15g of chalk reacte' &ith (excess)5$cm4 of #mol'mI4 *%l

8hen reaction cease' solution transferre' to a 5$cm4gra'uate' flask an' ma'e to the mark &ith pure &ater 5cm4of the solution titrate' &ith $1#mol'mI4!a,*(a) 15cm4reuire' < purity of the chalkJ

()%a%,4(s) " *%l(a)%a%l(a) " *,(l) " %,(g) *%l(a) " !a,*(a)!a%l(a) " *,(l) %a%,4 = #$$gmolI#

+mount of !a,* = amount of *%l unreacte' = $1$5'm4x $1#mol'mI4= 15 x#$I4mol in 5cm4

2otal amount of *%l unreacte' = 15 x#$I4mol x 5$35 = $1$5mol

,riginal amount of *%l taken = $1$5'm4x #mol'mI4= $1$5mol

+mount of *%l use' to react &ith the %a%,4= ($1$5 I $1$5)mol = $1$55mol +mount of %a%,4= $1$55mol3 = $1$#>mol9ass

%a%,4= $1$#>mol x #$$gmolI#= #1>$g < purity of %a%,4=#1>g3#15g x #$$ = >514


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(#)9arble reacte' &ith *%l aci' mass loss &as 144g &hat volume of %,&as evolve'J

(#)%a%,4(s) " *%l(a)%a%l(a) " %,(g) " *,(l) %a%,4= 144g3#$$gmolI#= $1$44mol $1$44mol %,pro'uce'

Folume of %,= $1$44mol x 'm4molI#= $15;'m4

()#$cm4of a hy'rocarbon %*xreacts &ith an excess of oxygen at #5$% # atm1 2he pro'ucts occupy a volume #$cm4greater than

the reactants at this temperature an' pressure1 in' x

()%*x(g) " ( " x3),(g)%,(g) " x3*,(g) ;han*e in volume = (volume of products + volume of reactants"

+voga'ros rule6 # volume " ( " x3)volumes volumes " x3 volumes #$cm4" ( " x3)#$cm4$cm4" 5xcm4

($cm4" 5xcm4) I (5$cm4" 15x cm4) = #$cm4 15x = $ hence x = >

!a%,4(s) &as 'issolve' in 'istille' &ater an' this solution &as put into a conical flask an' three 'rops of methyl orange in'icator

a''e' titrate' against *%l aci' until the en' point &as reache' !a%,

4 " *%l !a%l " *

, " %,

(4).escribe the colour change that tells &hen the en' point has been reache' (4)Solution &ill go from yello&orange

/ron metal reacts &ith copper(//)sulphate solution to form copper metal an' iron ions

+n experiment &as performe' to fin' &hich of the t&o euations is correct

%u"(a) " e(s) %u(s) " e"(a) 4%u"(a) " e(s) 4%u(s) " e4"(a)

B Po&'ere' iron of mass #1g &as place' in a beaker an' excess copper(//)sulphate solution &as a''e'

B 9ixture stirre' for 5 minutesB 2he contents of the beaker &ere then poure' into a funnel containing a &eighe' piece of filter paper

B 2he beaker an' the resi'ue &ere &ashe' &ith col' &ater an' the copper an' the filter paper &ere left overnight to 'ry

B !ext 'ay they &ere &eighe' an' the copper &as foun' to have a mass of #1;5g

(a)%alculate the mass of copper that shoul' be pro'uce' from #1g of iron if6

(i)Euation / is correct (ii)Euation // is correct

(a)(i)+mount of iron = #135;= $1$5mol $1$5N;415= #15?g (ii)+mount of copper = $1$5N43=$1$4@5mol $1$4@5N;415= 14>g

(b)8hich iron ion &as pro'uce' in the reactionJ (b)e"(c)(i)Suggest &hy the experimental value of the mass of copper &as slightly 'ifferent from the value you calculate' in (a)(c)(i)copper3filter paper &as still &et

(ii)Suggest one &ay in &hich the accuracy of this experiment coul' have been improve'(ii)Improved dryin*. 0ash 0ith suitable solvent(propanone or ethanol". suction filtration

(')8hy is it essential to use excess copper(//) sulphate solutionJ (')So that all the iron reacts !,2 the reaction is completeQ

(a)$15g of sulphamic aci' !*S,4*(s) &as 'issolve' in 'istille' &ater in a conical flask

415cm4!a,*(a) reuire' to react &ith sulphamic aci' solution !*S,4*(a) " !a,*(a) !*S,4!a(a) " *,(l)

(i)%alculate the amount of sulphamic aci' in $15g Mr(!*S,4*) = ?@ (i)$153?@ = $1$$5>mols

(ii)%alculate concentration of !a,* (ii)$1$$5>mols N #$$$3415 = $1##$mol'mI4

(b)Dalance use' to &eigh the sulphamic aci' is accurate to T$1$#g %alculate < error in mass of sulphamic aci' &eighe'

(b)$1-5

#$$$1$#- = >< allow

0.25

0.01100 = 4

- Properties 'epen' on the nature of bon's an' ho& these bon's are 'istribute' throughout the material

- Don's are forme' to attain greater stability atoms3molecules rearrange their electrons to give lo&er energy arrangements

(by electron loss gain or sharing)- /f a soli' has a regular structure its a crystal the structure is a crystal lattice

;hemical bond + force of attraction bet&een atoms ions or moleculesIonic bond 2he electrostatic attraction bet&een " an' I ions forme' by complete transfer of electron2ositive ions(cations)are attracte' to the (-)catho'e 'uring electrolysis(metal atoms &hich have lost one or more electrons(" %a")Ne*ative ions(anions)are attracte' to the positive ano'e 'uring electrolysis

;ovalent bond Sharing a pair of electrons one pair to a bon' (rather than complete transfer)

- %ovalent bon's are non-'ative bon's one-electron orbitals overlapping giving a electron bon'ing orbital(electron 'ensity

increases bet&een the bon'e' atoms)Double covalent bond Sharing of pairs of electrons in a bon'

Dative covalent bond Doth electrons in a covalent bon' are 'onate' from the same atom to an accepting atom(a electron orbital

'onating electron 'ensity into an empty orbital on the accepting atom)- !o 'ifference in length strength bet&een a normal covalent bon' an' a 'ative covalent bon'Molecular orbitals ,verlapping orbitals &here electron 'ensity exten's over at least atoms54ctet rule/ *y'rogen obtains electrons in its outer shell an' other atoms obtain >

/ntramolecular bon's B %ovalent

B /onic

B 9etallic

/ntermolecular bon's B Fan 'er 8aals forces

B .ipole 'ipole attraction

B *y'rogen bon'sstrongest

char*e

char*e density = volume


7/20

Electrone*ativity(E!) Po&er(of an atom)to attract(the pair of)electronsin a covalent bon'

- E! affects bon' length &ith larger 'ifferences giving shorter bon's

- 9ore electronegative atoms attract share' electrons more to&ar's itself an' acuire a partial negative charge

B Electronegativity 'ecreases going 'o&n a group(most electronegative element is fluorine)

B Electronegativity increases across perio' 4 elements on the 7*S lose electrons an' elements on the R*S gain electrons to achieve a

stable structure

U /onic bon's are partially covalent &hen E! is small U %ovalent bon's are partially ionic(creation of 'ipoles)&hen E! is large

2olarisability 2he ease &ith &hich the electron clou' of an anion is 'istorte' by a cation so theres electron sharing

B Smaller an' higher the charge(higher the charge 'ensity)on the cation the more polarising it is

B 7arger an' higher the charge on the anion the more easily it is polarise'

eatures favouring ionic bon'ing6B 7arge cation metal of lo& charge having a lo& /E

B 7arge anion non metal of lo& charge having a high E+

- 7arge anions most stable &ith large cations

Small cations most stable &ith small anions- + covalent bon' is polar if electrons in the bon' are uneually sha


8/20

,bp linear s!ape 1bp trigonal planar s!ape(molecule is flat) bp tetra!e"ral s!ape

>bp #rigonal

$ip%rami" s!ape

?bp octa!e"ron s!ape ,bp ,lp $ent s!ape

1bp )lp p%rami"al s!ape

P

**

*

1bp ,lp# s!ape"

Electron lone pairs Electron pairs not involve' in bon'ing

# Electron pairs in the valence shell(bp or lp)are as far apart as possible to minimise

repulsion3reach lo&est energy state ,r'er of repulsion bet&een electron pairs is6 bpIbp less than bpIlp less than lpIlp4 9ultiple bon's behave as single bon's(no 'ifference bet&een 'ative an' single bon's)

- + molecule &ill not be polar if its symmetrical an' 'ipoles of molecule cancel

Hybrid orbital + type of atomic orbital that results &hen or more atomic orbitals of an isolate' atom mix 'escribes orbitals in

covalently bon'e' atoms(hybri' orbitals 'ont exist in isolate' atoms) in a set are euivalent an' form i'entical bon'sHybridisation + mo'el that 'escribes the changes in the atomic orbitals of an atom &hen it forms a covalent compoun'

(Excite' % atoms orbitals rearrange' into i'entical hybri' orbitals(sp4hybri' orbitals) bon's arent i'entical unless you start

from i'entical orbitals)

sp !%$ri" or$ital ,ne of the hybri' orbitals forme' by hybri'isation of an s orbital an' p orbital

sp2 !%$ri" or$ital ,ne of the 4 hybri' orbitals forme' by hybri'isation of an s orbital an' p orbitals

same shape as sp4but lies in one plane at #$ @

sp& !%$ri" or$ital ,ne of the hybri' orbitals forme' by hybri'isation of an s orbital an' 4p orbital

Si*ma bond .irect overlap of orbitals

Double bond %ontains #X an' #bon'

&riple bond %ontains #X an' bon's

- Ethene only 4 orbitals hybri'ise' rather than all one s electron t&o p electrons other p electron unchange'(sp hybri'

orbitals)- +ll 'ouble bon's &ill consist of a pi bon' an' a X bon'

- /n 4r''iagram X bon's sho&n using lines each line representing one pair of share' electrons

- % atoms linke' by overlap of sp hybri' orbitals making a X bon' an' a pi bon' forme' by si'e&ays overlap of the non-hybri'ise'

p atomic orbitals1

- 2i bondB si'e&ays overlap of t&o p-orbitals B to give a t&o part orbit above an' belo& a bon' (likely to be attacke' by

electrophiles they are &eaker than X bon's)


9/20

Pi bon' forme' by si'e&ays overlap of the non hybri'ise' p

atomic orbitals

s atomic orbitals overlap X bon'

Hydro*en bond Electrostatic attraction bet&een a strongly " * atom attache' covalently to a highly electronegative element 3!3,

an' a strongly I 3!3, atom on another molecule * bon's are longer than covalent bon's

- +s &ater cools (long)* bon's form in greater uantity the open 0 or'ere' structure of ice gives it a lo&er 'ensity than liui' &ater

- %ompoun's &hich can * bon' &ith &ater are very soluble (glucose has ,* groups that * bon' &ith &ater)

- Extensive * bon's &ith 3!3,

cause higher Dts

Dipole8Dipole forces(permanently polar molecules) " an' I parts of the molecules attract electrostatically giving Dts higher than

those of non polar molecules of similar siAe1 or large molecules 'ispersion forces can excee' 'ipole-'ipole attraction

Dispersion7Ban der 0aals forces(non polar molecules)2emporary 'ipoles form bet&een molecules because of mobile electron 'ensit

&ithin the molecule1 " on one molecule &ill in'uce a I on a nearby one an' so on tho theres a net attraction bet&een molecules

*igher forces6 B 9ore electrons B 7arger area of contact(larger molecules3atoms) B 7inear instea' of branche' chains- .escen'ing noble gases or hy'ri'es bigger van 'er &aals forces as B +tomic3molecular siAe increases B 9ore shells of electrons

Ciant molecular substances Diamon"'B Hi*h Mt. hard. stiffas have to break strong covalent bon'ing throughout

&hole structure

B Cood thermal conductoras it rea'ily transmits vibration

B 2oor electrical conductoras no ions or free electrons as they are hel'

tightly bet&een atoms

B Insoluble in 0ater or*anic solventsas attractions bet&een solventmolecules an' carbon atoms &ill never be strong enough to overcome the

strong covalent bon's

(ilica7o&er 9t as has longer(therefore &eaker)bon's across &hole structure

Graphite

.iamon' 9t$$$% Si,9t#@$$%

/ce

)rap!iteB


10/20

ionic attraction bet&een the negatively charge' chains of silicate an' positive metal ions)

- 9echanical properties of the polymer 'epen' on B extent of cross-linking B &hether crystallites can form

- Pure substances have sharp 9ts but polymers 'ont(usually impure substances) melting over a range of temperatures instea' asvarying chain lengths of molecules means that they &ill have a melting range

Synthetic or*anic polymers B 9a'e from alkenes by a''ition reactions or from reactions bet&een organic molecules &hich have functional groups &hich can un'ergo con'ensation reactions B 2hey are mixtures since chain lengths vary(no sharp 9t)

Polymers forme' by ra'ical polymerisation B 7.PE is branche' cross-linke' B e& crystallites flexible translucentPolymers forme' by highly controlle' type of polymerisation B *.PE Aiegler natta catalyst B 9ore crystallites stiffer opaue

Natural polymers(organic)polysacchari'es(cellulose glycogen) nucleic aci's proteins all pro'uce' by con'ensation reactions/norganic polymers Silicates phosphoric aci' on heating

(#)8hy 0 &hich elements lose electronsJ

(#)9etals because B Msually they have # 4 electrons B Dy losing these electrons they achieve full outer shells an' become more stabB /n energy terms its easier to lose these electrons than gain more electrons

()8hy 0 &hich elements gain electronsJ

()!on metals because B Msually they have 5 ; @ electrons B Dy gaining electrons they achieve full outer shells an' become more stab

B /n energy terms its easier to gain these electrons than lose the outer electrons

(4)Suggest reasons &hy !a%l vapour is regar'e' as a collection of ion pairs rather than as !a%l molecules

(4)/f ion pairs colli'e theres nothing to stop them changing partnersQ &hereas if covalent molecules colli'e its improbable

()8hat happens to an electrostatically charge' ro' next to a polar liui' like &aterJ

()/tll move to&ar's the ro' because polar liui's contain molecules &ith permanent 'ipoles1 .oesnt matter if the ro' is positively

negatively charge'1 Polar molecules in the liui' can turn aroun' so the oppositely charge' en' is attracte' to&ar's the ro'(5)8hy 'oes &ater have a partial chargeJ (5),xygen has a higher electronegativity than hy'rogen

(;)(a)State the 'ifference in 'ensity bet&een soli' ice an' liui' &ater an' 'escribe ho& the presence of * bon's accounts for this

(a)B 8ater is more 'ense than soli' ice B 2he * bon's in soli' ice &hich hol's the molecules together are in fixe' positions an' lea'

an open structure B /n &ater the * bon's are constantly being broken an' ma'e

(b)Explain the structure of ice inclu'e a 'iagram

(b)B %ovalent in &ater molecules B * bon's bet&een molecules B each &ater &ith four &aters aroun' I tetrahe'ral

(@).escribe in terms of the position an' motion of particles &hat happens &hen some 9g%l(s) is heate' from R2 to :ust above 9t

(@)B +t R2 the ions are in a fixe' positions in a lattice B +s heat is applie' the ions vibrate more B Eventually ions have enough enerto overcome electrostatic attraction B /ons break free an' are able to move as soli' melts

(?)Sketch a graph of temp vs time as asubstance is heate' from

:ust belo& 9t to :ust above Dt

(#)(a)8hat part of the !*4 molecule enables it to form a 'ative covalent bon'J(a)7one pair on the nitrogen

(b)7ist intermolecular forces bet&een molecules of ammonia

(b)* bon's an' 'ispersion forces

()!ame elements in V9g(*,);W"&hich are :oine' by a covalent bon' ()* an'

(4)!ame elements in V9g(*,);W"&hich are :oine' by a 'ative covalent bon'

(4), an' 9g

(#)8hy is 9g/more covalent than 9g%lJ

(#)Decause /Iion is larger than %lIion so more easily polarise' lea'ing to covalency()9etal3!on-metal compoun's usually ionic yet soli' aluminium chlori'e has man

covalent characteristics becauseJ()Small ra'ius large " charge of +l4" means high polarising ability giving covalen

character pulling electron 'ensity a&ay from %lIcreating a mostly covalent bon'

(#)Explain &hy the 9t of 9g is higher than that of !a

(#)B 9g ions have larger charge('ensity) than !a 9g contributes electrons per atom to the sea of electrons !a has fe&er 'elocali

electrons !a is a larger atom B *ence 9g ions have greater attraction for the sea of electrons than !a

B 9elting reuires energy to overcome this attraction meaning a higher 9t

(4)Explain &hy Dt of phosphine is lo&er than that for ammonia

(4)B Phosphine 'oesnt have * bon's B 7ack of * bon's not compensate' by increase' in'uce' 'ipole-'ipole forces()State the strongest type of intermolecular force present in samples of %* ()Fan 'er &aals forces

(#)Explain ho& covalent structure of io'ine lea's to it having a lo& 9t (4)8eak intermolecular forces reuire little energy to break

()Glucose poly(ethene) orcesJ Properties as a conseuenceJ()Glucose covalent * bon'ing 'ipole-'ipole B Mnusually high 9t for its siAe

B * bon's bet&een polar ,* groups an' &ater makes it &ater soluble

Poly(ethene) covalent 'ispersion B 9olecules of 'ifferent siAes lea' to a 9t range B !on-con'uctor of electricity

B 7arge covalent molecules insoluble in any solvent because solventIsolute interactions arent strong enough to overcome the large

'ispersion forces bet&een such large molecules

(#)State an' explain the shape of the ammonia ion !*"

(#)B 2etrahe'ral B *as pairs of bon'ing electrons B Repel as far a&ay from each other as possible


11/20

B Dt increases

B Relative atomicmass an' siAe

increases

!oble

gases

Relative atomic

mass

2b3 Group

*y'ri'es

Relative

atomic mass

2b3

*e 1$ %* #;1$ >#1;

!e $1 @ Si* 41# #;#

+r 4?1? >@ Ge* @;1; #>5

r >41> ## Sn* #1@ #

Ke #4#14 #;; Pb*probably 'oesnt exist

2eriodicity Regular perio'ic variations of properties of elements &ith atomic number2eriodic #$I#@ #$I4

*akHmolI# #$@ #> 4;

Structure 9etallic(gives monatomic vapours)

Giant covalent(gives monatomic

vapour)

P S> %l 9onatomic

9olecular covalent

Atoms *et smaller hi*her Mt across period

B !umber of protons increasing meaning stronger nuclear attraction

B Extra electrons are at roughly the same energy level even if the outer electrons are in 'ifferent orbital types

B 7ittle extra shiel'ing effect little extra 'istance to lessen the attraction from the nucleusB Smaller atoms can pack more closely &hich means better orbital overlap

B 9ore electrons in the valence shell to 'elocalise aroun' the metal lattice

Sharp rise in Mt bet0een M* Na and only small rise bet0een M* Al

B +lkali metals are bo'y centre' cubic packing that 'oesnt bring atoms as close as possible B 9g 0 +l hexagonal close packing

9ts 'epen' on 'ispersion forces2hosphorus 8eak van 'er &aals forces so 9t is lo&Sulphur *ighest 9t largest van 'er &aals forces largest molecule

;hlorine 7o&est 9t &eakest van 'er &aals forces smallest molecule simple 'iatomic molecules &ith no permanent 'ipoles

Ar*on +rgon monatomic stable electron arrangement small intermolecular 'ispersion van 'er &aals forces so 9t is lo&

Grp #(alkali metals) Grp (alkaline earth metals)S block metal compoun's ionic ,x !os("# 0 " respectively)only because going

above these entails an /E input &hich coul'nt be recovere' from 7E of resulting soli'

- Fery reactive lo& 'ensity lo& 9t lo& E! soft because of &eak metallic bon'ing compoun's usually colourless unless transition

metal is present in the anion- /onic ra'ius smaller than atomic ra'ius for s block elements because loss of outer electrons results in loss of outer shell

Grp # +tomic ra'ius

pm

/onic

ra'ius

pm

.ensity

gcm4

/ncrease

9t % Dt % +bun'ance

ppm

#st/E

kHmol I#n'/E

kHmol I#

.ecrease

lame

colours

7i

!a

Rb

%s

#44

#5@

$4#;

45

;$

?5

#44#>

#;?

$154

$1?@

$1>;#154

#1>>

#>#

?>

;44?

?

#44$

>?$

@@;>>

;?$

;5

>4$$

5?$$4#$

@

5$

?;

#?$4

4@;

@?>

5;4

4$5#;4

$

%armine re'

Yello&

7ilac%olourless

%olourless

Grp

/ncrease

4r'/E

kHmol I#

.ecrease

De

9g%a

Sr

Da

>?

#4;#@

#?#

#?>

4#

;5?@

##4

#45

#1>5

#1@#15

1;

415

#@>

;?>4?

@;?

@5

@@

###$#>@

#4>$

#;$

;

$?$$4;4$$

#5$

4$

?$$

@4>5?$

55$

5$4

#@5@

#5###5

#$;

?;5

#>$$

@@$?$

#$

44?$

%olourless

8hiteDrick re'

%rimson re'

+pple green

Croup )

B +toms the largest of the perio'

B ody centred cubic pac'in*

B n'/Es a lot larger than #stbecause removing n'electron

reuires breaking into inert gas structure &hich has less

shiel'ing shell is closer to the nucleus so nuclear attraction is

much larger

B Grp # more reactive than Grp because # less proton 0 only

nee's to lose # electon to lose to achieve a full outer shell

Croup , .ensitiy har'ness 9ts higher than Group # becauseB +tomic ra'ius smaller in Group

B He!a*onal close pac'in*(except Da)

B electrons per atom for metallic bon'ing

B Extra proton

*exagonal close packe' arrangement Do'y centre' cubic


12/20

3face centre' cubic lattice arrangement


13/20

Descendin* Croup ) ,

B .ensity rises because mass of the atom increases more rapi'ly than its siAe- 9t 0 har'ness 'ecreases reactivity increases

B +tomic ra'ius increases smaller charge 'ensity 'elocalise' electrons more sprea' out

B Re'uce' attraction of " ions to sea of 'elocalise' electrons less energy to break bon's

- /E 0 E! 'ecreases

B Extra electron shells shiel'ing outer electrons from nuclear charge B ,uter electrons further a&ay from the nucleus an' less attracte'

B ,verall out&eighs increase in protons re'ucing nuclear attraction

Acidsproton 'onors

+ci's mixe' &ith &ater release *"(never alone in &ater)&hich combine &ith *,(hy'rate')to form hy'roxonium ions *4,"

*%l(g) " *,(l)

*"

(a) " %lI

(a) *%l(g) 'oesnt release hy'rogen ions until it meets &ater so *%l(g) isnt an aci'(trong aci"sH;l # 0ater H## ;l+

/onise('issociate)almost completely nearly every * atom release' to become a hy'rate' proton lots of *"(a) ions

*ea+ aci"s H,;41# 0ater H## H;41

+ &eak aci' euilibrium lies to the left so most of the aci' &ont be ionise'

/onise('issociate)slightly little * atoms release' little *"(a)ions

Stron* acids and concentrated acids 4R 0ea' acids and dilute acids aren/t the same

B Strong &eak refers to ho& much the aci' has ionise' B %oncentrate' 'ilute refers to molcmI4of the aci'

asesproton acceptors make ,*Ihy'roxyl ions &hen 'issolve' in &aterSalt + compoun' forme' by replacing hy'rogen in an aci' by a metal

Metal # Acid Salt # H,

9g(s) " *S,(a) 9gS,(a) " *(g)

9g(s) " *%l(a) 9g%l(a) " *(g)

9g(s) " *"

(a) 9g"

(a) " *(g)

Metal carbonate # Acid Salt # ;4,# H,4

!a%,4(s) " *%l(a) !a%l(a) " %,(g) " *,(l)

!a%,4(s) " *"(a) !a"(a) " %,(g) " *,(l)

%a%,4(s) " *%l(a)

%a%l(a) " %,(g) " *,(l)Acid7ase neutralisation reaction /onic euation for neutralisation *"(a) " ,*I(a) *,(l)

Metal 4!ide(al'ali" # Acid Salt # H,4

Grp # 9,(s) " *%l(a) 9%l(a) " *,(l)

Grp 9,(s) " *%l(a) 9%l(a) " *,(l)

Metal hydro!ide(al'ali" # Acid Salt # H,4

Grp # 9,*(a) " *%l(a) 9%l(a) " *,(l)

Grp 9(,*)(a) " *%l(a) 9%l(a) " *,(l)

S bloc' metals and o!y*en +ll oxi'es are basic except De is amphotericRadicals +toms3ions &ith a lone unpaire' electron very reactive

)ro,p 1reacts &ith oxygen in air at R2 silvery &hen cut they rapi'ly tarnish an' become 'ull 'ue to oxi'e coating

7i !a store' in paraffin oil &hile Rb %s &hich are more reactive are store' in seale' containers

7i reacts &ith nitrogen in the air ?


14/20

2ero!ides ,I(s) " *,(l),*

I(a) " *,(a) Na,4,(s" # ,H,4(l" ,Na4H(a3" # H,4,(a3"

Supero!ides ,I(s) " *,(l),*

I(a) " *,(a) " ,(g) ,4,(s" # ,H,4(l" ,4H(a3" # H,4,(a3" # 4,(*"


15/20

Group %ation

ra'ius3pm

*y'roxi'e solubility

mol per #$$g &ater

/ncrease

Sulphate solubility

mol per #$$g &ater

.ecrease

9g"

%a"

Sr"

Da"

;5

??##4

#45

1$$ x#$I5

#154 x#$I4

414@ x#$I4

#15$ x#$I

#1>4 x#$I#

1;; x#$I4

@1## x#$I5

?14 x#$I@

&hermal stability

+bility of a material to 'ecompose un'er heat stress1 9ore ionic more thermally stable more heat before 'ecomposition

- 2hermal stability of a carbonate &ill 'epen' on the stability of the carbonate lattice compare' &ith the oxi'e lattice at the same

temperature as cation siAe changes 7Es(strength of bon'ing in an ionic substance)of carbonates 0 oxi'es change by 'ifferent factor

- &hermal stability increases do0n the *roup as cations have a larger ionic ra'ius so charge 'ensity 'ecreases so lo&er polarisingpo&er 'istorting carbonate3nitrate anion less

Croup )- Group # cations larger less charge compoun's more thermally stable than Group so 'ifferences in 7E bet&een the carbonate 0

oxi'e arent sufficient to allo& 'ecomposition of the carbonates at Dunsen temperatures(except 7i &hich has the smallest cation)


16/20

(#)+r insulator becauseJ (#)B 9onatomic B ull outer shells of electrons tightly hel' in place so completely unintereste' in bon'ing

()8hy 'oes calcium stop reacting &ith ('il)*S,after a fe& secon's even though it 'i'nt react initially()B %alcium sulphate B orms an insoluble3protective layer

(#)State relative thermal stability of potassium nitrate an' calcium nitrate an' explain ho& its relate' to the siAes an' charges of the ioinvolve'

(#) B %alcium nitrate less thermally stable3'ecomposes more easily than potassium nitrate B %a cation smaller B &ith 'ouble charge polarises nitrate more B bon's in nitrate more easily broken3oxygen atom more attracte'

(#).escribe a test to 'istinguish bet&een 7i%l(s) an' !a%l(s) (#)lame test()State ho& a flame test &oul' 'istinguish bet&een %a(!,4)an' Da(!,4) ()%a brick re' Da (apple)green

(#)(a)(i)/'entify one of the elements that is compose' of simple molecules at R2

(i)P or S or %l()!ame the type of bon'ing in (i)%a%l(ii)*%l(g) ()(i)/onic(ii)%ovalent

(4)(i) factors &hich affect the polarising po&er of cationsJ (i)ionic ra'iuscharge

N a M g A l S i P S C l A

e l e m e n t

m

e

ltin

g

te

m

p

e

ra

tu

re

/

K

1 8 0 01 6 0 0

1 4 0 0

1 2 0 0

1 0 0 0

8 0 0

6 0 0

4 0 0

2 0 0

0

(#)(a) bottles are clearly labele' sulphate1 2he soli' in bottle + 'issolves easily in&ater but none of the soli' in bottle D appears to 'issolve &hen a''e' to &ater

8hich of these t&o bottles contains barium sulphateJ (a)D

(b)Dottle % labele' magnesium carbonate 8hen a sample is heate' a colourless gas

is pro'uce' that turns lime&ater clou'y1 State &hether this label is correct an' explain

(b)7ime&atermilky%, 9g%,4'ecomposes on heating to %, label correct

4!idation Is *"" 5eI9n"" *, !,

I" *,!,4I" eI " *"

Dalancing euations6 (x) 9n,I" #;*"" #$eI9n"" >*, (x5) 5!,

I" 5*,5!,4I" #$eI " #$*"

,verall6 9n,I" 5!,

I" ;*"9n"" 5!,4I " 4*,

(#)(i) 8rite ionic half euation for re'uction of bromine to bromi'e ions (i)Dr " eIDrI

(ii) 8rite ionic half euation for oxi'ation of e"ions to e4"ions (ii)e"e4" " eI

(iii) *ence &rite overall ionic euation for reaction of e"ions &ith bromine (iii)Dr" e"DrI" e4"


17/20


18/20

5Halo*en/ 9eans salt former because of large number of ionic salt compoun's Group @ formsEnthalpy of dissociation Enthalpy change &hen # mole of a gaseous substance is broken up into free gaseous atoms(measure of

strength of covalent bon's bon' enthalpy("ve))

State at R2 9t % Dt % +tomic

ra'ius

ppm

/onic

ra'ius

ppm

#st/E

kHmol I#E+

kHmol I#

/ncrease

Don'

'issociation

enthalpy

.ecrease

%olour in

&ater

%olour in

hexane

%l

Dr

/

Pale yello& gasGreen gas

Dro&n liui'

.ark grey soli'

-$-#$#

-@1

##

-#>>-41@

5>1>

#>

@??

##

#44

#4;#>#

#?5

#;

#;>$#;$

##$

#$#$

-340

-4;

-4

-4#

58

#?4

#5#

%olourless

,range

Dro&n

%olourless

Dro&n

Purple

*ighly reactive non-metals strong oxi'ising agents natural state is covalent 'iatomic molecules(%l) F'& forces bet&een molecules

- %ovalency means lo& solubility in &ater but 'issolves easily in organic compoun's(hexane)- *alogens in ("),x states 'ont form (")ions but are bon'e' covalently to more electronegative atoms as oxyanions ,%lI0 %l,4I

- E+ 0 bon' 'issociation enthalpies peak at %l normally the shorter a bon' the stronger it is but &ith the non bon'ing electrons

are brought so close that they repel &eakening the bon'(partly &hy is very reactive)

EN o!idisin* po0er descendin* *roup

,xi'ising strengths seen by 'isplacement reactions

&ith hali'e ions

%l(g) " !a/(a)!a%l(a) " /(a)

%l(a)%olourless

Dr(a),range

/(a)Dro&n

3!a%l(a) 3!aDr(a) 3!a/(a)(colourless)

K

KK

,range Dr(a)forme'

KK

Dro&n /(a) forme'

Dro&n /(a) forme'K

*alogens un'ergo 'isproportionation &ith alkalis

,x State of K

%,7. *,2

-,# ,Na4H(a3" Na-4 # Na- # H,4

K" ,*I K,I" KI " *,

$ "# I#

1-,# ?Na4H Na-41# >Na- # 1H,4

4K" ;,*IK,4

I" 5!KI" 4*,

$ "5 I#

;hlorine test B S&imming pool smell moist litmus paperbluere'bleache'B 9oist starch io'i'e paper io'i'e ions oxi'ise' to io'ine so turnsblue-black

B %l&ill oxi'ise DrIto Dran' /

Ito / solutions turn orange3bro&n excess %luse' then /(s)ppts

;l,(a3" # ,r+(a3" r,(a3" # ,;l

+(a3" obtains bromine from sea &ater use' for lea'e' petrol antifreeAe

%l" eI%lI DrIDr " e

I

romine test B Slo&er than chlorine moist litmus paperbluere'bleache'

B 9oist starch io'i'e paper io'i'e ions oxi'ise' to io'ine so turnsblue-black

B Dr&ill oxi'ise /Ito /solution 'arkens immiscible organic solvent(hexane) can sho& presence of io'ine turning solutionpurple

B Dromine &ill react &ith paper moistene' &ith fluorescein 'ye turning it scarlet pro'uct is eosin(ingre'ient of re' ink)Iodine test B !o effect on litmus

B 9oist starch io'i'e paper an' starch solution turnsblue-black&hich neither chlorine or bromine &ill 'o

B /o'ine is purple in immiscible organic solvents(hexane methylbenAene) &hich have no oxygen1 Presence an' test of oxygen in a

solvent gives a bro&ner cast

- *ali'es are compoun's &ith a halogen ion(/ *%l !aDr)- *y'rogen hali'es(covalent hy'ri'es *IK)aci'ic colourless gases&hitemisty fumes in moist air giving &hitefumes &ith !*4(g)

Polar molecules high solubility strong aci's 'ue to high *hy'of the *"ions an' relatively small hali'e ions &hich compensate for

the bon' 'issociation energy of the molecule extent to &hich 'issociation occurs 'epen'ent on *IK

H-(a3" # H,4(l" H14#(a3" # -+(a3" *%l(g) " *,(l) *

"(a) " %lI(a)

H;l. Hr. HI all stron* acids. stron*er do0n the *roup B Re'ucing po&er of hali'e increases 'escen'ing B 7arger atomic ra'iuselectrons further a&ay from the nucleus B Extra shiel'ing

ond enthalpyStrength of the bon' energy nee'e' to make the bon'(+verage of bon' 'issociation enthalpies of a bon')

Don' enthalpy for %I* bon' is average value from breaking all %I* bon's %*(I#;kHmolI#) Falue taken from *a(%*)

*I *I%l *IDr *I/

Don' enthalpy (kHmol I#) 5; 4# 4;; ??

B * aci' o''ly behaves as a &eak aci' *I bon' is the strongest but not enough to explain the 'ifference in aci' strength

2his reaction prevents *I molecules from 'issociating

I

ions form * bon's &ith un'issociate' * moleculesH+F(a3" # F+(a3" GF88888 H+F + (a3"

B * not normally corrosive but 'issolves glass an' gives burns from formation of Si;Iion &hich is &ater soluble other hali'e ions

are too large to fit aroun' the Si atom * solutions kept in poly(ethane)bottles

Halide ion test(Not F" (Since +g is &ater soluble)

B +ci'ify &ith ('il)*!,4(a) to ensure removal of ions &hich &oul' give a spurious ppt

B +'' +g!,4(a) silver hali'e ppt forme' -+(a3" # A*#(a3" A*-(s" B +'' ('il)3(conc)!*4to ppt

Reaction re'uces concentration of +g"ions A*#(a3" # ,NH1(a3" GA*(NH1",#(a3"

%l I+g!,4(a) ('il)!*4to ppt8hiteppt +g%l forms Ppt 'issolves leaving colourless solution

,R B ,xi'ise to respective halogenB +ci'ify &ith ('il)*!,4(a) to ensure removal of ions

&hich &oul' give a spurious ppt

B +'' immiscible organic solvent(hexane)

B +'' so'ium chlorate(/) solution an' shake

B DrI=bro&norganic layer /I =purpleorganic layer

Dr I+g!,4(a) (conc)!*4to ppt%reamppt +gDr forms Ppt 'issolves leaving colourless solution

/ I +g!,4(a) (conc)!*4to ppt

Yello&ppt +gDr forms Ppt insoluble


19/20


20/20

Halide salt 0ith (conc"H,S4at R2

B

edexcel chemistry - unit1 as

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