chapter 3

Question 1

molar mass

Answer 1

refers to the mass of exactly one mole of a species and has units of grams/mol and has the same numerical value as the molecular weight

Question 2

molecular formula

Answer 2

gives the number of atoms of each element present in a single molecule

Question 3

empirical formula

Answer 3

consists of the ratio of atoms of each element present, simplified to the lowest whole numbers possible

Question 4

percent composition by mass

Answer 4

refers to the percent of the total mass of a compound that a particular element contributes

Question 5

how to calculate percent composition by mass given the empirical formula

Answer 5

ex. glucose CH2O the percent mass composition by mass of oxygen is equal to the mass contributed by oxygen divided by the total mass of the molecule (16g) / (12g + 2g + 16g) = 53%

Question 6

finding the empirical formula by percent composition without being given mass of compound present or the compounds molar mass

Answer 6

what is the empirical formula of a compound that contains 54.5% C 9.15% H 36.3% O assume yer compounds mass is 100g then calculate the number of moles of each element present, assuming 100g of compound C 54.5 g/ 12 g/mol = 4.5 mol H 9.15 g / 1 g/mol = 9 mol O 36.3 g / 16 g/mol = 2.25 mol divide all by the smallest mol value, get ratio and make empirical formula

Question 7

chemical reaction

Answer 7

a process by which one or more chemical species (reactants) are converted into one or more chemically different species (products)

Question 8

phase changes are…

Answer 8

phase changes (NOT chemical reactions)

Question 9

synthesis/combination reaction

Answer 9

two or more reactants combine to form a single product

Question 10

decompostition reactions

Answer 10

involves the breakdown of one reactant into multiple smaller products

Question 11

single displacment or “replacement” reactions

Answer 11

one element or group replaces another within a compound

Question 12

double displacement reaction

Answer 12

both groups replace another within a compound (new pairs)

Question 13

single or double displacement reactions often occur between

Answer 13

metals or halogens

Question 14

neutralization reaction

Answer 14

an acid and a base react with each other and produce a salt and water

Question 15

combustion reaction

Answer 15

A combustion reaction is a reaction in which a substance reacts with oxygen gas, releasing energy in the form of light and heat. Combustion reactions must involve O2 as one reactant.

exothermic reactions

The products of the combustion of hydrocarbons are carbon dioxide and water.

Question 16

redox reactions

Answer 16

involve a transfer of electrons from one species to another

the species that gives up electrons is oxidized

the species that gains electrons is reduced

both reactants expereince a change in oxidation state

Question 17

limiting reagent

Answer 17

the reactant that is limiting the reaction and so the product relies on

Question 18

how to solve limiting reagent questions

Answer 18

1. balance the chemical reaction
2. take grams and find out how many moles of each reactnat are present by dividing the grams by molar mass
3. divide the moles calculated by the coefficient in front of that reactant

if asked how many grams of product will be produced…

Question 19

percent yield

Answer 19

percent yield = actual mass of product / theoretical mass of product x 100%

Question 20

how to solve percent yield questions

Answer 20

1. actual mass will be given
2. calculate theoretical yield using stoichiometry
3. plug into formula and calculate