Ch 5/6: Chemical Reactions (Chem 114)

percent yield

(amount of product actually obtained in a chemical expression / theoretical yield) * 100%

standard temperature and pressure (STP)

0 degrees Celsius (273 K) and 1 atm (760 mm Hg)

values of the gas constant R

0.0821 L*atm/molK or 8.31 L*kPa/molK

molar mass

1 mole of a substance, mass of 6.022 * 10^23 molecules of a substance, molecular (formula) weight of substance in grams

standard molar volume of a gas at STP

22.4 L

(solubility guidelines) always soluble

NH4+, group 1 ions, NO3-, CH3CO2-, perchlorate

oxidation number (oxidation state)

Positive or negative number that indicates how many electrons an atom has gained, lost, or shared to become stable; INIDICATES WHETHER THE ATOM IS NEUTRAL, ELECTRON RICH, OR ELECTRON POOR

(balancing chemical equations) step 2

add appropriate coefficients to balance numbers of atoms of each element

rules for assigning oxidation numbers

an atom in its elemental state has an oxidation number of zero, monatomic ion has an oxidation number equal to its charge; in a molecular compound, an atom usually has the same oxidation number it would have if it were a monatomic ion; for compounds with more than one nonmetal element, the more electronegative element has its preferred negative oxidation number; the less electronegative element is assigned a positive oxidation number so the sum of the oxidation numbers in a neutral compound is 0

aqueous solution

aq

(balancing chemical equations) hint

balance pure elements last

mole to mass and mass to mole conversions

carried out using molar mass as a conversion factor

mole to mole conversion

carried out using mole ratios as conversion factors

(mass to mass conversions) step 4

check answer using ballpark solution

(balancing chemical equations) step 3

check equation to make sure the numbers and kinds of atoms on both sides of the equation are the same

(mass to mass conversions) step 2

choose molar masses and mole ratios to convert known information into needed information

molar mass serves as a _______ between numbers of moles and mass

conversion factor

charge on oxidizing agent ______ during reaction

decreases

when acids and bases are mixed together in correct proportion, acidic and basic properties

disappear

ionic equation

equation in which all ions are explicitly shown

net ionic equation

equation that does not include spectator ions

(solubility guidelines) insoluble

everything else (ex: CaCO3)

chemical equation

expression in which symbols are used to represent a chemical reaction

theoretical yield

found by mass to mass calculations

actual yield

found by weighing product obtained

mass to mass conversions

frequently needed but cannot be directly carried out

gas

g

reduction

gain of electrons

(solubility guidelines) usually soluble

halides (Cl-, Br-, I-), SO4 2-

coefficients in a balanced chemical equation tell how many molecules there are and

how many moles of each reactant are needed and how many moles/molecules of each product are formed

charge on reducing agent _____ during reaction

increases

spectator ion

ion that appears unchanged on both sides of a reaction arrow

liquid

l

oxidation

loss of electrons

(balancing chemical equations) step 4

make sure coefficients are reduced to their lowest whole-number values

coefficients can be put in the form of ______ which act as conversion factors when setting up calculations

mole ratios

avogadro's number

number of molecules or formula units in a mole (NA = 6.022 * 10^23)

coefficient

numbers in front of chemical formulas that multiply all the atoms in a formula

mole

one mole of any substance is the amount whose mass in grams (molar mass) is numerically equal to its molecular or formula weight

acid-base neutralization reaction

process in which H+ ions from an acid react with OH- ions from a base to yield water; an ionic compound called a salt is also produced

precipitation reaction

process in which an insoluble solid called a precipitate forms when reactants are combined in aqueous solution

oxidation-reduction reaction (redox reaction)

process in which one or more electrons are transferred between species; as a result of this transfer, charges on atoms in the various reactants change

ideal gas law

relationships among the four variables P, V, T, n for gases can be combined into a single expression : PV=nRT

solid

s

(mass to mass conversions) step 3

set up factor label expression and calculate answer

product

substance that is formed in a chemical reaction and is written on the right side of the reaction arrow in a chemical equation

reducing agent

substance that is oxidized, gives up an electron, causing reduction

oxidizing agent

substance that is reduced, gains an electrons, causing oxidization

reactant

substance that undergoes change in a chemical reaction and is written on the left side of the reaction arrow in a chemical equation

molecular weight

sum of atomic weights of all atoms in a moleule

formula weight

sum of atomic weights of all atoms in one formula unit of any compound

limiting reagant

the reactant that is exhausted first

amount of product actually formed is somewhat less than the

theoretical yield

avogadro's law

volume of gas is directly proportional to its molar amount at a constant pressure and temperature

neutralization reaction produces

water, salt

(balancing chemical equations) step 1

write an unbalanced equation using correct formulas for all reactants and products

(mass to mass conversions) step 1

write balanced chemical equation