Chapter 7: Mass Stoichiometry

Question 1

formula mass

Answer 1

the sum of the atomic masses of all the atoms in a chemical formula

aka formula weight, molecular mass, or molecular weight

Question 2

atomic mass unit (amu)

Answer 2

a standard unit of mass used to measure the mass of atoms, molecules, and subatomic particles; equal to 1/12 of the mass of a carbon-12 atom

Question 3

percent composition

Answer 3

the percentage by mass of each element in a compound; equal to the mass of one element divided by the mass of the entire compound x 100%

Question 4

mole

Answer 4

a quantity consisting of 6.02 x 10^23 units

Question 5

Avogadro’s number

Answer 5

the number of particles in a mole - 6.02 x 10^23

Question 6

mole concept

Answer 6

the mole is an amount similar to familar units such like a pair or dozen; it provides a specific measure of the number of atoms or molecules in a bulk sample of matter

Question 7

the mole concept allows us to express the atomic mass in

Answer 7

grams; we can say that the mass of an element is grams per mole (lab scale)

Question 8

molar mass

Answer 8

mass expressed in grams per mole

Question 9

when we write the conversion factor, the unit we wish to cancel goes on the

Answer 9

bottom; the one we wish to keep goes on the top

Question 10

to convert between grams and moles, we use

Answer 10

molar mass

Question 11

to convert between moles and particles, we use

Answer 11

Avogadro’s number

Question 12

to convert between moles of two different substances, we use

Answer 12

the mole ratio from the balanced equation

Question 13

mole ratio

Answer 13

the ratio of the amounts (in moles) of any two substances involved in a chemical reaction, as seen from the coefficients of the balanced chemical equation

Question 14

stoichiometry problem

Answer 14

a problem that relates the amount of one reagent or product to another in a chemical reaction using a balanced equation

Question 15

excess reagent

Answer 15

reactants that are not used up when the reaction is finished

Question 16

limiting reagent

Answer 16

the compound that is consumed first; determines the amount of product that can form in a reaction

Question 17

to find the limiting reagent, we calculate

Answer 17

the amount of product that each starting material can product; the starting material that can produce the least amount of product is the limiting reagent

Question 18

to find leftovers in a stoichiometry problem, we

Answer 18

subtract what we used from our starting material

Question 19

theoretical yield

Answer 19

the amount of product that can form in a chemical reaction based on the balanced equation and the amount of starting materials present

Question 20

we find the theoretical yield by

Answer 20

identifying the limiting reactant and using the mole ratio to determine the moles of product that can be formed from it

Question 21

actual yield

Answer 21

the amount of product that is actually produced when a chemical reaction is carried out

Question 22

percent yield

Answer 22

a measure of the efficiency of a reaction; it compares the actual yield and the theoretical yield

Question 23

percent yield formula

Answer 23

actual yield / theoretical yield x 100%