2010-2011 Chemistry SOL Blitz

Question #1• Which of the following atoms

contains 30 protons, 40 neutrons and 28 electrons?

• A: 70 Zn+2

• B: 70 Zn-2

• C: 40 Zn+2

• D: 30 Zr-2

Answer to Q#1• Letter A: 70 Zn+2 is the answer.• Why? The format for chemical

symbols is A Xcharge

z

• Remember, A = mass, which equals protons + neutrons

• Z = atomic number = protons• Charge = protons – electrons

Question #2• The element boron has only two stable

isotopes. One stable isotope has a mass number of 10 and the other has a mass number of 11. Which of the following could be the atomic weight of the element?

• A: 9.5• B: 10.8• C: 11.7• D: 12.4

Answer to Q#2• Letter B: 10.8 is the answer• Why? The mass of an element

on the periodic table is the weighted average of all the isotopes of that element

Question #3• An atom of Argon—40 contains—• A: 18 protons and 18 neutrons• B: 18 protons and 22 neutrons• C: 18 protons and 40 neutrons• D: 20 protons and 20 neutrons

Answer to Q#3• Letter B: 18 protons and 22

neutrons• Why? The 40 in Argon-40 is the

mass of the isotope• Remember mass = protons +

neutrons (electrons have no mass)• Argon has an atomic number of

18, so there 18 protons

Isotope/ Ion Quick Review• Isotopes of an element have the same

atomic number (protons) but different masses (hence different neutrons)

• Both protons and neutrons have a mass of 1

• Electron’s mass is not taken into account in the mass of an atom

• Ions are anything with an electrical charge

• Positively charged ions have lost electrons

• Negatively charged ions have gained electrons

Question #4• A scientist comparing K and Ca

would find that K has a—• A: lower electronegativity and a

smaller atomic radius• B: higher electronegativity and a

smaller atomic radius• C: lower electronegativity and a

larger radius• D: higher electronegativity and a

larger atomic radius

Answer to Q#4• Letter C: lower electronegativity

and a larger atomic radius• Why? Electronegativity gets higher

as you go across a period and atomic radius gets smaller as you go across a period

• K is farther left so it must have a lower electronegativity and larger atomic radius

Question #5• Which of the following elements is

the most reactive?• A: Cs• B: Sr• C: Mg• D: Rb

Answer to Q#5• Letter A: Cs• Why? All these elements are

metals—the most reactive metals are the largest

• Atomic radius gets larger as you go down a group

• Cs is farthest down so it is the largest and most reactive

Trends Quick Review• Trends as you go down a group:

larger atomic radius, lower electronegativity, lower and ionization energy (easier to lose an electron)

• Trends as you go across a period: smaller atomic radius, higher electronegativity, and higher ionization energy (harder to lose an electron)

• Remember IE is the energy it takes to lose an electron

• Electronegativity is the ability to gain an electron

Quick Review Continued• Metal reactivity: Largest metals

= most reactive metals.• Remember metals like to lose

electrons• Non-metal reactivity: smallest

non-metals = most reactive non-metals.

• Remember non-metals like gain electrons

• Noble gases are non-reactive—they have a full valence shell

Question #6• A bond between an element of

group 2 and an element of group 17 will be:

• A: ionic• B: Nonpolar covalent• C: Polar covalent• D: Metallic

Answer to Q#6• Letter A: Ionic• Why? Group 2 elements are

metals (also known as alkaline earth metals) and group 17 (or 7) elements are non-metals (also known as halogens)

• Metals + non-metals = ionic bonding

Bonding Quick Review• Covalent bonding = sharing of

electrons between non-metals• Ionic bonding = transferring of

electrons between metal + non-metal

• Nonpolar covalent bond = equal sharing of electrons between non-metals

• Polar covalent bond = unequal sharing of electrons between non-metals

Question #7• What is the name for Cu2S?• A: Copper sulfide• B: Copper (I) sulfide• C: Dicopper sulfide• D: Dicopper monosulfide

Answer to Q#7• Letter B: Copper (I) sulfide• Why? Copper is a transition (d

block) metal, so you must use roman numerals to indicate its charge

• Look behind S for the charge of Cu.

• Charge is +1 so copper (I) sulfide

Question #8• Which of the following is the

formula for carbonic acid?• A: HC• B: HCO• C: HO• D: H2CO3

Answer to Q#8• Letter D: H2CO3• Why? It’s an acid so H must come

first. Carbonic = carbonate = CO3-2

• H+1 + CO3-2 = H2CO3

Question #9• What is the molecular formula of

tetraphosphorus decoxide?• A: PO• B: P4O• C: P4O10

• D: PO10

Answer to Q#9• Letter C: P4O10• Why? Tetra = 4 and deca = 10• So P4O10• Remember, when using prefixes

don’t switch—simply write what’s given

Naming Quick Review• Must use roman numerals to

indicate charge of a transition metal

• Only use prefixes when the compound is all non-metals

• If an acid has hydro prefix then it’s H+element

• If no hydro prefix for an acid then it’s H+polyatomic

Question #10___C3H4 + ___O2 ___CO2 + ___H2O

• When the equation above is balanced, what is the sum of the coefficients?

• A: 4• B: 5• C: 8• D: 10

Answer to Q10• Letter D: 10• Why? C3H4 + 4O2 3CO2 + 2H2O;

so 1+4+3+2 = 10• Don’t forget the law of

conservation of mass says the reactants side = products side

Question #11• Which of the following is an

example of a decomposition reaction?

• A: 2AgCl 2Ag + Cl2

• B: CuO + H2O Cu(OH)2

• C: AgCl + Mg MgCl2 + Ag• D: HCl + Na(OH) H2O + NaCl

Answer to Q #11• Letter A: 2AgCl 2Ag + Cl2 • Why? Decomposition is when you

start with one reactant and break into 2 products

• Letter B = synthesis; letter C = single replacement and letter D = neutralization reaction

Question #12• 12 x 403 =• What is the answer to the above

problem expressed with proper sig figs?

• A: 5,000• B: 4800• C: 4830• D: 4836

Answer to Q#12• Letter B: 4800• Why? When multiplying or

dividing, you use lowest # of sig figs for your answer

• 12 only has two sig figs, so your answer can only have two

Question #13• How many atoms of Na are in

0.300 moles of Na?• A: 0.0131 atoms• B: 7.86x1021 atoms• C: 1.81x1023 atoms• D: 6.02x1023 atoms

Answer to Q#13• Letter C: 1.81x1023 atoms• Why? 0.300 moles Na x

6.02x1023atom 1 mole

= 1.81x1023 atoms

Question #14• How many moles are in a

342grams of CaO?• A: 6.10 moles• B: 56.1 moles• C: 1.92x104 moles• D: 3.67x1024 moles

Answer to Q#14• Letter A: 6.10 grams• Why? 342g x 1mole CaO = 6.10

moles 56.08 grams

• 56.08 grams is the molar mass of CaO from the Periodic Table

Moles Quick Review• When multiplying/dividing use lowest

# of sig figs for answer• When adding/ subtracting use lowest

# of decimal places for answer• MassMoles use mass of Periodic

Table = 1 mole• Moles Particles use 1 mole =

6.02x1023 particles• Moles Liters at STP use 1 mole =

22.4 L

Question #15Be + 2HCl BeCl2 + H2

• Using the above reaction, what mass of beryllium was consumed in the reaction if 4.0 moles of HCl were used?

• A: 2.0grams• B: 9.0 grams• C: 18.0 grams• D: 36.0 grams

Answer to Q#15• Letter C: 18.0 grams• Why? • 4.0molsHCl x 1mols Be x 9.01gBe

2 mols HCl 1 mole Be

= 18.0 grams Be

Letter #162C2H6 + 7O2 4CO2 + 6H2O

• In an experiment, 0.500 mols of C2H6 were reacted with 1.50 moles of oxygen gas. Which of the following is the limiting reactant in this experiment?

• A: C2H6

• B: O2

• C: CO2

• D: H2O

Answer to Q #16• Letter B: O2• Why? 0.500molsC2H6 x 4mols CO2

2 mols C2H6

= 1.00 mols CO2• 1.50molsO2x4mols CO2 =

0.857molsCO2

7 mols O2 • Since O2 produces less CO2, it must

be the limiting reactant• C and D shouldn’t even be choices

b/c they are products!

Stoich Quick Review • Mass A Mols A Mols B Mass B• Go from mols A mols B using mol

to mol ratio from coefficients of balanced equation

• Limiting reactant is the one used up first. It also produces the smaller amount of product

• % yield = (actual/theoretical) x100• Can also use stoich to go from

mass/mols of A to liters of B; use 22.4 L = 1mol at STP

Question #17• Which of the following is NOT a

part of the kinetic molecular theory?

• A: Gases move in a straight, continual motion

• B: Gases have no volume themselves

• C: Gases participate in inelastic collisions

• D: Kinetic energy is directly related to temperature

• E: Gases feel no attractive forces

Answer to Q#17• Letter C: Gases participate in

inelastic collisions• Why? Gases actually participate in

elastic collisions. • The other 4 parts are all TRUE

Gas Laws Quiz Review• Boyle’s Law P1V1 = P2V2, where P

and V are inversely related.• Charles’ Law V1/T1 = V2/T2

• Gay-Lusac P1/T1 = P2/T2

• Combined Gas Law (P1V1)/T1 = (P2V2)/T2

• Ideal Gas Law PV = nRT, where R = 0.0821 (L*atm)/(mol*K)

More Gas Laws Review• Must always convert

temperature from celsius to KELVIN!

• Absolute zero is -273C or 0K!• Absolute zero is the point where

all motion slows down and stops• Dalton’s Law P1+P2+P3… = Ptotal

Question #18• Which of the

following phase changes occurs at the arrow?

• A: Sublimation• B: Melting• C: Evaporation• D:

Condensation

Answer to Q#18• Letter B: melting• Why? Graph

always goes S, L, G—look at pic on right

• The arrow points to line b/w solid and liquid

• Only phase changes there are melting (SL) or freezing (LS)

Phases Quick Review• 6 phases changes

– Melting (SL) --Freezing (LS)– Evaporation (LG) --Condensation (GL)– Sublimation (SG) --Deposition (GS)

• Molar heat of fusion = amount of energy needed to melt 1 mole of a substance

• Molar heat of vaporization = amount of energy needed to evaporate 1 mole of a substance

• Specific heat capacity = amount of energy needed to raise the temperature of 1 gram of a substance by 1˚C use q = mxCpxΔT

IMF Quick Review• Four different intermolecular

forces– London dispersion (weakest) =

nonpolar covalent molecules– Dipole-dipole = polar molecules– Hydrogen bonding = H connected to N,

O or F bonding to another O, N or F– Ionic (strongest) = metal + non-metal

• Don’t forget to do the arrow test to determine polarity of a molecule

Question #19• How many moles of MgCl2 are

present in 3.00 liters of a 0.150M MgCl2 solution?

• A: 0.0500 moles• B: 0.450 moles• C: 1.35 moles• D: 20.0 moles

Answer to Q#19• Letter B: 0.450 moles• Why? Molarity (M) = mols/liters• So 0.150 M = x/3.00 L• (0.150M)(3.00L) = x• X = 0.450 moles

Solutions Quick Review• Molarity(M)=mols of solute/L of

solution• Molality(m)=mols of solute/kg of

solvent• Freezing point depression:

ΔTf=(-Kf) (m)(n)• Boiling point elevation ΔTB=(Kb)(m)

(n)• Remember if the solute is covalent, n

= 1

Equilibrium Quick Review• Write K expressions as products

over reactants. Remember the coefficients in the balanced equation are used as exponents in the K expressions

• Solids and liquids are not included!• Catalysts lower the activation

energy of a reaction• Enthalpy (ΔH) and entropy (ΔS)

determine the spontaneity of a reaction

• - ΔH (exothermic) and +ΔS (more disorder) means a spontaneous reaction

Question #20• PCl5(g) + heat PCl3(g) + Cl2(g)• Which of the following will cause

an increase in the equilibrium concentration of Cl2 gas?

• A: The addition of PCl3 gas• B: The removal of PCl5 gas• C: A decrease in temperature• D: An increase in temperature

Answer to Q#20• Letter D: An increase in

temperature• Why? Heat is a reactant, so

increase reactant side, equilibrium shifts to product side

• Letter A causes shift to L; letter B causes shift to L; and letter C causes shift to L

Acid/Base Quick Review• pH = -log[H+]• pOH = -log

[OH-]• pH + pOH =

14• [H+][OH-] =

1x10-14

• [H+] = 10^(-pH)

• [OH-] = 10^(-pOH)

• pH < 7 = acid• pH > 7 = base