Ch 7 Section 3

Question 1

a chemical formula indicates the elements as well as the

Answer 1

relative number of atoms or ions of each element present in a compound

Question 2

chemical formulas allow chemists to calculate a number of

Answer 2

characteristic values for a given compound

Question 3

like individual atoms, molecules, formula units, or ions

Answer 3

have characteristic average masses

Question 4

the mass of a water molecule is found by

Answer 4

adding the masses of the three atoms in the molecule

Question 5

the mass of a water molecule can be correctly referred to as

Answer 5

a molecular mass

Question 6

the mass of one NaCl formula unit is not a molecular mass because NaCl is an

Answer 6

ionic compound

Question 7

the mass of any unit represented by a chemical formula, whether the unit is a molecule, a formula unit, or an ion,

Answer 7

is known as the formula mass

Question 8

the formula mass of any molecule, formula unit, or ion is

Answer 8

the sum of the average atomic masses of all atoms represented in its formula

Question 9

the procedure illustrated for calculating the formula mass of a water molecule can be used to calculate the

Answer 9

mass of any unit represented by a chemical formula

Question 10

molar mass of a substance is equal to

Answer 10

the mass in grams of one mole, approx. 6.022 x 10^23 particles

Question 11

the molar mass of a compound is calculated by summing the masses of the

Answer 11

elements present in a mole of the molecules/ formula units that make up the compound

Question 12

one mole of water molecules contains exactly two moles of

Answer 12

h atoms and one mole of o atoms

Question 13

a compound’s molar mass is numerically equal to its

Answer 13

formula mass

Question 14

the molar mass of a compound can be used as a conversion factor to

Answer 14

relate an amount in moles to a mass in grams for a given substance

Question 15

to convert a known amount of a compound in moles to a mass in grams,

Answer 15

multiply the amount in moles by the molar mass

Question 16

amount in moles x molar mass (g/mol)

Answer 16

mass in grams

Question 17

to convert a known mass of a compound in grams to an amount in moles,

Answer 17

the mass must be divided by the molar mass

Question 18

or you can invert the molar mass and multiply so that

Answer 18

units are easily canceled

Question 19

mass in grams x 1/molar mass (g/mol)

Answer 19

amount in moles

Question 20

to find the mass percentage of an element in a compound, one can divide the mass of the element in a sample of the compound by the

Answer 20

total mass of the sample, then multiply this value by 100.

Question 21

(mass of element in sample of compound)/(mass of sample of compound) x 100=

Answer 21

% element in compound

Question 22

the mass percentage of an element in a compound is the same regardless of

Answer 22

the sample’s size

Question 23

a simpler way to calculate the percentage of an element in a compound is to determine how many

Answer 23

grams of the element are present in one mole of the compound. divide this value by molar mass and multiply by 100

Question 24

(mass of element in 1 mol of compound)/ (molar mass of compound) x 100=

Answer 24

%element in compound

Question 25

the percentage by mass of each element in a compound is known as the

Answer 25

percentage composition of the compound