Unit 7 (Chapter 8)

Question 1

Avogadro’s Number

Answer 1

6.022*10^23

Question 2

empirical formula

Answer 2

formula based on observation or experiment \

Question 3

formula mass (molecular mass)

Answer 3

• mass of one molecule or formula unit
• in other words, the mass of one particle of a compound (a substance represented by a formula)
• written in amu(s)
• need formula and periodic table
• sum of individual atomic masses
• associated with ionic and molecular compounds
• value found by adding

Question 4

molar mass

Answer 4

mass of a mole (the mass from the periodic table in grams instead of amus)

Question 5

molar volume

Answer 5

the volume of a mole

Question 6

molecular formula

Answer 6

tells us the actual number of elements present in a formula

Question 7

percent composition

Answer 7

the percent of the total mass of the compound that is due to that element

Question 8

Avogadro’s Law

Answer 8

if you have two gases at the same temperature and pressure, they will occupy the same volume only if they contain the same number of molecules

Question 9

Atomic mass

Answer 9

• the mass of an atom (NOT the same as mass number)
• value found on periodic table
• associated only with elements

Question 10

molecular compound

Answer 10

molecule

Question 11

ionic compound

Answer 11

formula unit

Question 12

formula unit

Answer 12

• particle of ionic compound
• associated only with ionic compounds

Question 13

Mole city and particle-ville

Answer 13

1 mol = 6.022*10^23 atoms; molecules; formula units

Question 14

Mole city and mass town

Answer 14

1 mol = grams from periodic table (g)

Question 15

Mole city and gas volume corners

Answer 15

1 mol = 22.4L at STP

Question 16

Atomic mass unit

Answer 16

• label that goes at end of number
• associated with elements, ionic compounds, molecular compounds

Question 17

Empirical formula steps

Answer 17

• start with mass values or percent composition values
• find masses if not already masses
• convert g to mol (use molar mass)
• divide by smallest mol

Question 18

Empirical formula tips

Answer 18

If mol/smallest mol = .5, multiply each by 2
If mol/smallest mol = .33333 multiply each by 3
If mol/smallest mol = .25, multiply each by 4
Empirical formula must be reduced ratio
do not limit sig figs until final step

Question 19

Molecular formula formula

Answer 19

actual molar mass (given in problem) /
empirical molar mass (added from empirical formula)