chem final study guide

8/12/2019 Chem Final Study Guide

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Chemistry A Final Study Guide

Chapter 8 Chemical Equations and Reactions

types of reactionso synthesis

A + XAX reactions of elements with O and S two reactants, one product metals with halogens oxides of active metals react with water to form hydroxides oxides of nonmetals react with water to form oxyacids

o decomposition AXA + X electrolysis decomposition of a substance by an electric current decomp of metal carbonate products of metal oxide and CO2 decomp of metal hydroxide products of metal oxides and water decomp of metal chlorate products of metal chloride and oxygen decomp of acid products of nonmetal oxides and water

o single displacement A + BYAY + B displacement of a metal in a compound by another metal displacement of hydrogen in water by a metal displacement of hydrogen in an acid by a metal displacement of halogens reactivity of halogens decreases down the group,

therefore any halogen can replace any element below it

o double displacement AX + BYAY + BX formation of a precipitate formation of a gas formation of water

o combustion a reaction in which a substance combines with oxygen releasing a large amount of

energy in the form of heat and light

burning of hydrocarbons writing chemical equations in word and chemical formulas

o identify elements in equationo write formula using compound nameso balance equation

activity series and single displacement reactionso a list of elements arranged by the ease with which the elements undergo certain chemical

reactions

o usually determined in single displacement reactionso most active element placed at top and can replace any element below it but not above it


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o trend in activity of halogens

o reactivity of halogens decreases down the group, therefore any halogen can replace anyelement below it

o they undergo synthesis reactions with many metalso form ionic compounds with group 1 and group 2 metals

Chapter 9 Stoichiometry

solving stoichiometry problems set up below

mole ratio 2 2 1

balanced equation 2HgO 2Hg + O2

molesmass 95.2 g

check


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percent yield actual yield / theoretical yieldo theoretical yield max amount of product that can be produced from a given amount of

reactant

o actual yield measured amount of a product obtained from a reaction

Chapter 10 States of Matter

kinetic molecular theory foro solids

strong intermolecular forces hold particles in relatively fixed positions with onlyvibrational motion

definite melting point kinetic energy of particles overcomes the attractive forcesbetween them

high density low incompressibility low rate of diffusion

o liquids

relative high density relative incompressibility transmits pressure equally in all directions particles close together and attractive forces between particles can slow diffusion surface tension force that tends to pull adjacent parts of a liquids surface together,

decreasing surface area to the smallest possible size

capillary action the attraction of the surface of a liquid to the surface of asolid

o gases large particles that are far apart relative to their size collisions between gas particles and between particles and containers are elastic

elastic collisions no net loss of kinetic energy particles are in continuous, random, rapid motion there are no forces of attraction between gas particles the temperature of the gas depends on the average kinetic energy of the particles of

gas

ideal gas hypothetical gas that perfectly fits all of the assumptions of the kinetic moleculartheory of gas

o most gases exhibit ideal gas behavior when at high temperature and low pressureo noble gases and nonpolar diatomic molrcules show essentially ideal behavioro polar molecules deviate from ideal behavior

intermolecular forces in liquidso dipole-dipoleo London dispersion forceso Hydrogen bonding

properties ofo solids

definite shape and volume crystalline solids crystals where particles are arranged in ordered geometric

patterns

ionic crystals positive and negative ions; electrostatic charge covalent network crystals each atom covalently bonded to its neighbor; in

diamonds and oxides of transition metals


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metallic crystals metal cations surrounded by a sea of electrons; cause ofhigh conductivity in metals

covalent molecular crystals covalently bonded molecules held together byintermolecular forces

o non polar weak London dispersion forceso polar dispersion forces, dipole-dipole, and hydrogen bonding

amorphous solids particles randomly arranged; without shapeo liquids definite volume

takes the shape of its container attraction between particles are caused by intermolecular forces stronger intermolecular forces and lower mobility than gases not bound in fixed positions particles have mobility/fluidity

o gases expansion due to assumption of continuous, random, rapid motion and no forces

of attraction between particles

fluidity ability of gas particles to glide past each other; due to assumption thatthere are no forces of attraction between particles

low density - due to assumption that particles are tiny and far apart compressibility - due to assumption that particles are tiny and far apart diffusion spontaneous mixing of two substances due to their random motion; due

to assumption that particles are in continuous, random, rapid motion

effusion process by which gases pass through a tiny opening; due to assumptionthat particles are in continuous, random, rapid motion

liquid vapor equilibrium pressure exerted by a vapor in equilibrium with its correspondingliquid at a given temperature

o smell indicator of vapor pressure; higher vapor pressure, the stronger the smello particles above average kinetic energy vaporized, they lose kinetic energy and go back into

liquid

o volatile liquid evaporates readily, weak intermolecular forceso non volatile molten ionic compounds

vapor pressure curves


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Chapter 11 Gases

Daltons law of partial pressure total pressure of a mixture of gases is equal to the sum of thepartial pressures of the component gases

gas lawso BoylesPV=k

P1V1=P2V2 constant T, n

o CharlesV=kT V1/T1= V2/T2 constant P, n

o Gay LussacP=kT P1/T1= P2/T2 constant V, n

o AvogadrosV=kn Avogadros number = 6.022 x 1023molecules, atoms, ions/mol


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o combined gas law P1V1/T1= P2V2/T2 calculating molar mass of a gas

o standard molar volume of a gas at STP, one mole of gas occupies 22.4 Lo multiply using 22.4 L/1 mol as the conversion

ideal gas law PV=nRTo R = 0.08206 L x atm / mol x Ko used to calculate when there is no change

Chapter 14 Acids

electrolytes all aqueous acids are electrolytes naming acids

o ate ico ite - ous

acid-base theorieso Arrhenius

acid increases concentration of hydrogen ions (H+) strong acid releases lots of H+; completely ionize in aqueous solution weak acid releases few H+in aqueous solution

base increases concentration of hydroxide ions (OH-) strong bases dissociate in water strong bases are strong electrolytes

o Bronsted-Lowry acid molecule or ion that is a proton donor base molecule or ion that is a proton acceptor Bronsted-Lowry acid-base reaction protons are transferred from one reactant (the

acid) to another (the base)

o Lewis acid atom, ion, or molecule that accepts an electron pair to form a covalent bond

any compound where the central atom has three valence electrons can reactas a Lewis acid

base atom, ion, or molecule that donates an electron pair to form a covalent bond Lewis acid-base reaction formation of one or more covalent bonds between an

electron pair donor and electron pair receiver

conjugate acid-base pairso conjugate base of an acid the species that remains after a Bronsted-Lowry acid has given

up a proton

o conjugate acid of a base the species that remains after a Bronsted-Lowry base has gaineda proton

o conjugate acid-base pairs in equilibrium both the forward and reverse reactions occuro

strong acid weak baseo weak acid strong base

amphoteric can act as either acid or baseChapter 15 Acid Base Titration

calculating pHo pH = -log [H30+]o [H30+] = 10-pH

titration calculationo MAVA= MBVB


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Chapter 16 Reaction Energy

temperature the measure of the average kinetic energy of the particles in a sample of matter heat energy transferred between samples of matter because of a difference in temperatures specific heat the amount of energy required to raise the temperature of one gram of a substance

by 1 degree C or 1 K

o Cp= q / m x To specific heat = heat transferred / mass x T

H enthalpy change amount of energy absorbed or released by a system as heat during aprocess at constant pressure

o H = HproductsHreactantso enthalpy change depends on number of moles

Hesss Law the overall change in enthalpy change in a reaction is equal to the sum of enthalpychanges for the individual steps in the process

o Hesss Law problem write steps of equation with H balance equations to cancel out

**if multiply equation, make sure you multiply H what cant cancel should be final equation add H to find total H

entropy measure of the randomness of the particles in a systemo represented by So measured in kJ / (mol x K)o positive S system increases more randomo negative S system decreases more orderedo solid particles in fixed positions low entropyo liquid particles close together a bit higher in entropyo gas particles far apart and in random, rapid motion high entropy

spontaneous reactionsH S G Is this reaction spontaneous?negative positive negative yes, at all temperatures

negative negative positive or negative only if T < H / S

positive positive positive or negative only if T > H / S

positive negative positive never

o reaction spontaneous if G < 0 Gibbs free energy enthalpy-entropy function at a particular temperature and constant pressure

that assesses the tendency of a reaction to proceed in a particular direction

o G = H TS *at a constant temperature and pressureChapter 17 Reaction Kinetics

reaction mechanism step by step sequence of reactions by which overall chemical changes occur intermediates species that appear in some steps but not in the net equation homogeneous reaction reactants and products exist in a single case collision theory set of assumptions regarding collisions and reactions activation energy minimum energy required to transform reactants into an activated complex

o required to merge valence electrons and to loosen bonds sufficiently for molecules to reacto has to overcome repulsive forces between molecules


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activated complex transitional structure that results from an effective collision; it persists whileold bonds are breaking and new bonds are forming

o not an intermediate factors affecting reaction rate

o nature of reactants reaction rate depends on particular reactants and bonds involvedo surface area

heterogeneous reactions involve reactants in two different phases; reactions canonly occur when surfaces are in contact

increase in surface area increases rate of heterogeneous reactionso temperature an increase in temperature increases average kinetic energy of particles and

can result in a greater number of effective collisions

energy of collisions must be equal to or greater than activation energyo concentration in homogeneous reactions, reaction rates depend on concentration of the

reactants

depends in slowest step in reaction mechanismo presence of catalysts

catalysts substance that changes the rate of a reaction without itself being permanentlyconsumed; does not appear as a product

o provides alternate pathway of lower energy where the potential energy is lowered and mayhelp to form an activated complex that requires lower activation energy

rate limiting step if the reaction proceeds in a series of steps, the slowest-rate step is the ratelimiting step

writing a rate lawo rate law an equation that relates reaction rate and concentrations of reactantso determined by how concentration affects the reaction rateo R = k [A]n[B]mo k = specific rate constanto [A] and [B] molar concentrations

Chapter 18 Chemical Equilibrium reversible reactions a reaction in which the products can react to reform the reactants equilibrium conditions pressure, concentration, temperature equilibrium constant K = [C]c[D]d/ [A]a[B]b

o independent of initial concentrationso dependent on temperature

Le Chtliers principle a system subjected to stress will shift in the direction that tends to relievethe stress

reactions running to completion when ions are removed from the reaction either as a gas orprecipitate causing the reaction to cease

chem final study guide

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