#1 What is the molar mass of sucrose? (C12H22O11)
12.0 x 12 = 144.0
1.0 x 22 = 22.0
16.0 x 11 = 176.0
total:
342 g/mole
#2 What is the molar mass of each of the following compounds?
a. Phosphorous pentachloride (PCl3)
P; 31.0
Cl; 35.5
31 + (35.5 x 3) = 208.2 g/mole
b. Uranium hexaflouride (UF6)
U; 238.0.0
F; 19.0
238 + (19.0 x 6) = 352.0 g/mole
#3 Calculate the molar mass of each of the following ionic
Compounds:
a. KMnO4
158.0 g/mole
b. Ca3(PO4)2
310.2 g/mole
#4 How many moles is 3.52 x 1024 molecules of water?
3.52 x 1024 molecules x
1 mole
= 5.85 moles H2O
1
6.02 x 1023 molecules
#5 How many atoms of zinc are in 0.60 moles of zinc?
.60 moles x
1
6.02 x 1023 atoms =
1 mole
3.6 x 1023 atoms
#6 What is the mass of 1.00 moles of oxygen (O2)?
1.00 moles x
1
32.0 grams
1 mole
=
32.0 grams
SECTION 2 MOLE-MASS and MOLE-VOLUME RELATIONSHIPS
#1 What is the molar mass of each of the following compounds?
a. C6H12O6
b. NaHCO3
c. C7H12
d. KNH4SO4
180.2 g/mole
84.0 g/mole
96.2 g/mole
153.2 g/mole
#2 Calculate the mass in grams of each of the following:
a. 8.0 moles lead oxide (PbO)
8.0 moles x 223.2 g
= 1.8 x 10-3 g
1
b. .75 moles (H2S)
1 mole
.75 moles x 34.1 g
1
1 mole
c. .001 moles (SiH4)
d. 1.50 x10-2 moles (O2)
e. 2.30 moles (C2H6O2)
=
25.6 g
3.2 x 10-2 g
.48 g
1.43 x 102 g
#3 How many grams are in 1.73 moles of
dinitrogen pentoxide (N2O5)
1.73 moles x
1
(14.0 x 2) + (16.0 x 5)
= 108 g/mole
108 grams = 1.87 x 102 grams
1 mole
#4 How many grams are in .658 moles of calcium phosphate
(Ca3(PO4)2
.658 moles x
1
310.3 g
1 mole
=
204.2 grams
#5 Calculate the number of moles in each of the following:
4.9 x 10-3 moles
a. .50 g NaBr
9.10 x 10-2 moles
b. 13.5 g Mg(NO3)2
c. 1.02 g MgCl2
1.08 x 10-2 moles
d..
.00100 g CH3Cl
1.98 x 10-5 moles
e.
1.50 x 10-3 g
1.97 x 10-5 moles
C3H6(OH)2
#6 A chemist plans to use 435.0 grams of ammonium nitrate
NH4NO3 in a reaction. How many moles of the compound is that?
435.0 g
1
x
1 mole
80 g
=
5.43 moles
#7 .0465 moles of C20H24N2O2 is how many
grams?
The molar mass is 12x20 + 24+ 28+ 32 =
324 g/mole
.0465 moles x 324 g = 15.1 g
1
1 mole
#8 What is the volume at STP of 2.66 moles of methane (CH4) gas?
2.66 moles x 22.4 liters
1
1 mole
=
59.6 liters
#9 How many moles is 135 L of ammonia
(NH3) gas at STP?
135 liters x
1 mole = 6.03 moles NH3
1
22.4 liters
10.3 Percent Composition and
Chemical formulas
1. A sample of a compound analyzed in a chemistry laboratory
consists of 5.34 g of carbon, 0.42 g of hydrogen, and 47.08 g of
chlorine. What is the percent composition of this compound?
The total is: 52.84 g
% comp. C is: 5.34
52.8
x 100 = 10.1%
% comp. H is: .42 x 100 = .79%
52.8
% comp. Cl is: 47.08
52.8
x 100 = 89.1%
#2 Find the percent composition of a compound containing
tin and chlorine if 18.35 g of the compound contains 5.74 g tin.
5.74 g tin
18.35
x 100% = 31.3 % tin
by difference you can get the % of chlorine:
100 % - 31.3 % = 68.7% chlorine
#3 If 3.907 g of carbon combines completely
with .874 g of hydrogen to form a compound,
what is the percent composition of this compound?
The total is: 4.781
% comp. C is: 3.907
4.781
x 100 = 81.7%
% comp. H is: .874 x 100 = 18.3%
4.781
#4 From the formula for calcium acetate Ca(C2H3O2)2 calculate
the mass of carbon that can be obtained from 65.3 g of the
compound.
The molar mass is: 40.1 + [(24+3+32) x 2] = 158.1 g mole
The % comp. of Ca is: 40.1 x 100 = 25.3%
158.1
The % comp. of C is: (12x4) x 100 = 30.3%
158.1
The % comp. of H is: (1.0 x 6) x 100 = 3.79%
158.1
The % comp. of O is: (16.0 x 4) x 100 = 40.5%
158.1
Therefore: 65.3 g x .303 =
19.8 grams of carbon
#5 How many grams of aluminum are in 25.0g
of aluminum oxide Al2O3?
The % composition of Al2O3 is:
% comp. Al is:
54.0
(27.0 x 2) + (16x3)
% comp. O is:
48.0
(27.0 x 2) + (16x3)
x 100 = 52.9%
x 100 = 47.1%
Therefore the # of grams of Al in 25.0 g Al2O3
is: 25.0 x .529 = 13.2 g
#6 How many grams of iron are in 21.6 g of iron (III) oxide (Fe2O3)
First determine the % composition:
% comp. Fe is:
% comp. O is:
111.6
159.6
x 100 = 70.0%
48.0
159.6
x 100 = 30.0%
Therefore 21.6 g x .70
=
15.11 grams
#7 Determine the empirical formula for each of the
following compounds from the percent composition:
a. 7.8 % carbon and 92.2 % chlorine
CCl
1. assume a 100 g sample
4
2. convert to moles
3. divide by the smallest number
4. multiply each number by a simple whole number
(if necessary) to get whole number ratios.
7.8 %
7.8 g
92.2 %
92.2 g
x 1 mole = .65/.65 = 1
12.0 g
x 1 mole = 2.6/.65 = 4
35.5 g
#7 Determine the empirical formula for each of the
following compounds from the percent composition:
b. 10.0 % carbon; .80 % H; 89.1 % chlorine
1. assume a 100 g sample
2. convert to moles
3. divide by the smallest number
4. multiply each number by a simple whole number
(if necessary) to get whole number ratios.
CHCl3
10.0 %
10.0 g
.80 %
.80 g
89.1 %
89.1 g
x 1 mole = .83/.80 = 1
12.0 g
x 1 mole = .80/.80 = 1
1.0 g
x 1 mole = 2.51/.80 = 3.1
35.45 g