chem 141 practice exam 2 2025
Questions and Answers
For each name, write the formula.
a.) chromium (II) sulfate heptahydrate
b.) ammonium sulfite
c.) nickel (II) phosphite
d.) aluminum carbonate
e.) silver oxide
f.) lithium chlorite
g.) potassium phosphate
h.) calcium chloride dihydrate
i.) hypochlorous acid
j.) zinc zulfate - --CORRECT ANSWER--a.) CrSO4 ⋅ 7H2O
b.) (NH4)2SO3
c.) Ni3(PO3)2
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, d.) Al2(CO3)3
e.) Ag2O
f.) LiClO2
g.) K3PO4
h.) CaCl2 ⋅ 2H2O
i.) HClO
j.) ZnSO4
Determine the percentage by mass of the Vitamin C molecule (C6H8O6) for each
of its elements. (L11 C1) - --CORRECT ANSWER--C6H8O6: 6(12.01 u) +
8(1.008 u) + 6(16.00 u) = 176.12 u
6(12.01 u) / 176.12 u × 100% = 40.92% C
6(16.00 u) / 176.12 × 100% = 54.51% O
8(1.008 u) / 176.12 u × 100% = 4.579% H
40.92% + 4.579% + 54.51% = 100.01%
An unknown hydrate of cobalt(II) chloride is found to have a molar mass of 238
g/mol. What is its formula? (L11 A7) - --CORRECT ANSWER--CoCl2: 58.93 u +
2(35.45 u) = 129.83 u
238 g/mol - 129.83 g/mol = 108 g/mol
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Questions and Answers
For each name, write the formula.
a.) chromium (II) sulfate heptahydrate
b.) ammonium sulfite
c.) nickel (II) phosphite
d.) aluminum carbonate
e.) silver oxide
f.) lithium chlorite
g.) potassium phosphate
h.) calcium chloride dihydrate
i.) hypochlorous acid
j.) zinc zulfate - --CORRECT ANSWER--a.) CrSO4 ⋅ 7H2O
b.) (NH4)2SO3
c.) Ni3(PO3)2
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, d.) Al2(CO3)3
e.) Ag2O
f.) LiClO2
g.) K3PO4
h.) CaCl2 ⋅ 2H2O
i.) HClO
j.) ZnSO4
Determine the percentage by mass of the Vitamin C molecule (C6H8O6) for each
of its elements. (L11 C1) - --CORRECT ANSWER--C6H8O6: 6(12.01 u) +
8(1.008 u) + 6(16.00 u) = 176.12 u
6(12.01 u) / 176.12 u × 100% = 40.92% C
6(16.00 u) / 176.12 × 100% = 54.51% O
8(1.008 u) / 176.12 u × 100% = 4.579% H
40.92% + 4.579% + 54.51% = 100.01%
An unknown hydrate of cobalt(II) chloride is found to have a molar mass of 238
g/mol. What is its formula? (L11 A7) - --CORRECT ANSWER--CoCl2: 58.93 u +
2(35.45 u) = 129.83 u
238 g/mol - 129.83 g/mol = 108 g/mol
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