Unit 2
Name _______________________________ # ________
Section 1: Molar Mass
Calculate the atomic and molar masses of the following chemicals:
Atomic Mass
Molar Mass
1)
Cl2
___________
___________
2)
KOH
___________
___________
3)
BeCl2
___________
___________
4)
FeCl3
___________
___________
5)
BF3
___________
___________
6)
CCl2F2
___________
___________
7)
Mg(OH)2
___________
___________
8)
UF6
___________
___________
9)
SO2
___________
___________
10)
H3PO4
___________
___________
11)
(NH4)2SO4
___________
___________
12)
CH3COOH
___________
___________
13)
Pb(NO3)2
___________
___________
14)
Ga2(SO3)3
___________
___________
15)
Cu(NO3)2  5H2O
___________
___________
Section 2: Mole
1)
Define “mole”.
2)
How many moles are present in 34 grams of Cu(OH)2?
3)
How many moles are present in 2.45 x 1023 molecules of CH4?
4)
How many grams are there in 3.4 x 1024 molecules of NH3?
5)
How much does 4.2 moles of Ca(NO3)2 mass?
6)
What is the molar mass of MgO?
7)
How are the terms “molar mass” and “atomic mass” different from one
another?
8)
Which is a better unit for expressing molar mass, “amu” or “grams/mole”?
Section 2: Moles, Molecules, and Grams
1)
How many molecules are there in 24 grams of FeF3?
2)
How many molecules are there in 450 grams of Na2SO4?
3)
How many grams are there in 2.3 x 1024 atoms of silver?
4)
How many grams are there in 7.4 x 1023 molecules of AgNO3?
5)
How many grams are there in 7.5 x 1023 molecules of H2SO4?
6)
How many molecules are there in 122 grams of Cu(NO3)2?
7)
How many grams are there in 9.4 x 1025 molecules of H2?
8)
How many molecules are there in 230 grams of CoCl2?
9)
How many molecules are there in 2.3 grams of (NH4)2SO3?
10)
How many grams are there in 3.3 x 1023 molecules of N2I6?
11)
How many molecules are there in 200 grams of CCl4?
12)
How many grams are there in 1 x 1024 molecules of BCl3?
13)
How many grams are there in 4.5 x 1022 molecules of Ba(NO2)2?
14)
How many molecules are there in 9.34 grams of LiCl?
15)
How many grams do 4.3 x 1021 molecules of UF6 mass?
16)
How many molecules are there in 230 grams of NH4OH?
Section 4: Mole Calculation
1) What are the molecular weights of the following compounds?
a. NaOH
d. Mn2Se7
b. H2O
e. MgCl2
c. H3PO4
f. (NH4)2SO4
2) How many atoms are in 2.4 moles of sulfur?
3) How many moles are in 15 grams of lithium?
4) How many moles are in 22 grams of argon?
5) How many grams are in 88.1 moles of magnesium?
6) How many atoms are in 2.3 grams of phosphorus?
7) How many grams are in 11.9 moles of chromium?
8) How many moles are in 9.8 grams of calcium?
9) How many grams are in 238 moles of arsenic?
10) How many grams are in 4.5 moles of sodium fluoride?
11) How many formula units are in 98.3 grams of aluminum hydroxide?
12) How many grams are in 0.02 moles of beryllium iodide?
13) How many moles are in 68 grams of copper (II) hydroxide?
14) How many formula units are in 3.3 moles of potassium sulfide?
15) How many moles are in 1.2 x 103 grams of ammonia, NH3?
16) How many grams are in 2.3 x 10-4 moles of calcium phosphite?
17) How many molecules are in 3.4 x 10-7 grams of silicon dioxide?
18) How many grams are in 1.11 moles of manganese (II) sulfate?
Section 5: Percent Composition Worksheet
Find the percent compositions of all of the elements in the following compounds:
1)
CuBr2
Cu: ___________
Br: ___________
2)
NaOH
Na: ___________
O: ___________
H: ___________
3)
(NH4)2S
N: ___________
H: ___________
S: ___________
4)
N2S2
N: ___________
S: ___________
Section 6: Empirical and Molecular Formulas
Determine the empirical formula for each compound.
1. A compound contains 0.0130 mol carbon, 0.0390 mol hydrogen, and 0.0065 mol
oxygen.
2. A compound consists of 72.2% magnesium and 27.8% nitrogen by mass.
3. Glucose contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass.
4. Phosphoric acid is found in some soft drinks. A sample of phosphoric acid
contains 0.3086 g of hydrogen, 3.161 g of phosphorus, and 6.531 g of oxygen.
Determine the molecular formula for each compound described.
5. A compound has an empirical formula of NO2 and a molar mass of 92.02 g/mol.
6. A compound has an empirical formula of C2H3O and a molar mass of 172 g/mol.
7. Ibuprofen, a common headache remedy, has an empirical formula of C 7H9O and
a molar mass of approximately 215 g/mol.
8. Nicotine is 74.2% carbon, 8.64% hydrogen, and 17.2% nitrogen by mass. Its
molar mass is about 160 g/mol.
9. Epinephrine (adrenaline) is a hormone secreted into the bloodstream in times of
danger and stress. It is 59.0% carbon, 7.15% hydrogen, 26.2% oxygen, and
7.65% nitrogen by mass. Its molar mass is about 183 g/mol.
Questions
10. Can the molecular formula of a compound ever be the same as the empirical
formula? Explain your answer.
11. What is the empirical formula of a compound that has three times as many
hydrogen atoms as carbon atoms, but only half as many oxygen atoms as
carbon atoms?
Section 7: Calculating Empirical and Molecular Formulas
1. Determine the Molar mass of the following compounds
a. P2O3 ___________________
b. BaSO4 ___________________
c. Mg(C2H3O2)2 ___________________
d. lithium carbonate ___________________
2. Calculate the empirical formula for the following compounds
a.
11.66 g iron, 5.01 g oxygen
b. 15.8% carbon and 84.2% sulfur
c.
43.6% phosphorus and 56.4% oxygen
d. 28.7% K, 1.5% H, 22.8% P and 47.0% O
4. Calculate the molecular formula for the following
a. empirical formula CH, molar mass = 78 g/mol
b. caffeine, 49.5% C, 5.15% H, 28.9% N, 16.5% O by mass,
molar mass = 195 g.
Section 8: Molarity Calculations
Calculate the molarities of the following solutions:
1)
2.3 moles of sodium chloride in 0.45 liters of solution.
2)
1.2 moles of calcium carbonate in 1.22 liters of solution.
3)
0.09 moles of sodium sulfate in 12 mL of solution.
4)
0.75 moles of lithium fluoride in 65 mL of solution.
5)
0.8 moles of magnesium acetate in 5 liters of solution.
6)
120 grams of calcium nitrite in 240 mL of solution.
7)
98 grams of sodium hydroxide in 2.2 liters of solution.
8)
1.2 grams of hydrochloric acid in 25 mL of solution.
9)
45 grams of ammonia, NH3, in 0.75 L of solution.
Determine how many grams of the substance you need to make the solution.
10)
2 L of 6 M HCl
11)
1.5 L of 2 M NaOH
12)
0.75 L of 0.25 M Na2SO4
13)
45 mL of 0.12 M sodium carbonate
14)
250 mL of 0.75 M lithium nitrite
15)
56 mL of 1.1 M iron (II) phosphate
16)
6.7 L of 4.5 M ammonium nitrate
17)
4.5 mL of 0.05 M magnesium sulfate
18)
90 mL of 1.2 M BF3
Section 9: Molarity Problems
1)
How many grams of potassium carbonate are needed to make 200 mL of a
2.5 M solution?
2)
How many liters of 4 M solution can be made using 100 grams of lithium
bromide?
3)
What is the concentration of a 450 mL solution that contains 200 grams of
iron (II) chloride?
4)
How many grams of ammonium sulfate are needed to make a 0.25 L solution at
a concentration of 6 M?
5)
What is the concentration of a solution that has a volume of 2.5 L and contains
660 grams of calcium phosphate?
6)
How many grams of copper (II) fluoride are needed to make 6.7 liters of a 1.2 M
solution?
7)
How many liters of 0.88 M solution can be made with 25.5 grams of lithium
fluoride?
8)
What is the concentration of a solution that with a volume of 660 mL that
contains 33.4 grams of aluminum acetate?
9)
How many liters of 0.75 M solution can be made using 75 grams of lead (II)
oxide?
10)
How many grams of manganese (IV) oxide are needed to make 5.6 liters of a
2.1 M solution?
11)
What is the concentration of a solution with a volume of 9 mL that contains
2 grams of iron (III) hydroxide?
12)
How many liters of 3.4 M solution can be made using 78 grams of isopropanol
(C3H8O)?
13)
What is the concentration of a solution with a volume of 3.3 mL that contains
12 grams of ammonium sulfite?