Percent Composition &
Molar Mass
Molar Mass
What is the molecular weight of carbon dioxide?
44
If a sample is composed of 24 grams of Mg and 16 grams of O, what is its empirical formula?
MgO
Balance the following reaction:
Mg + C → Mg2C
2 Mg + C → Mg2C
N2 + 3 H2 → 2 NH3
If 3 moles of NH3 are produced, how many moles of H2 had to have reacted?
5 mol H2
If a student obtains 20. grams of kryptonite but hypothetically could obtain 80. grams of kryptonite, what is the student's percent yield?
25 % yield
Ignoring significant figures, what is the mass percent of carbon in C5H5Cl? (L not I)
60% by mass
If a sample is found to be 44% B and 56% N by mass, what is its empirical formula?
BN
Balance the following reaction:
NaHCO3 + NH4F → NaF + CO2 + H2O + NH3
NaHCO3 + NH4F → NaF + CO2 + H2O + NH3
(already balanced with just 1s for the coefficient)
4 Fe + 3 O2 → 2 Fe2O3
If 16 moles of Fe react with 15 moles of O2, which reactant is limiting AND how many moles of reaction are possible?
Limiting reactant = Fe
4.0 mol rxn
If a laboratory is theoretically supposed to make 12 moles of NaBrO but produces it at a 66.6% yield, how many moles of NaBrO did the lab actually make?
8.0 mol NaBrO
What is the molecular weight of C5H8NO4Na?
169
If a compound is composed of 90% C by mass and the rest H, what is its empirical formula?
C3H4
Balance the following reaction:
Al4C3 + H2O → CH4 + Al(OH)3
Al4C3 + 12 H2O → 3 CH4 + 4 Al(OH)3
2 Na2O + 3 O2 → 4 NaO2
If 48 grams of O2 react, how many moles of NaO2 are obtainable?
2.0 mol NaO2
If an experiment yields 666 grams of Xe when it is supposed to yield 222 grams of Xe, what is the percent error?
200. % error
Ignoring significant figures, what is the mass percent of beryllium in Be2C?
60% by mass
If a hydride of aluminum is composed of 10% H by mass, what is its empirical formula?
AlH3
Balance the following reaction:
C4H10 + O2 → CO2 + H2O
2 C4H10 + 13 O2 → 8 CO2 + 10 H2O
C3H8 + 5 O2 → 3 CO2 + 4 H2O
If 11 g C3H8 react with excess O2, how many grams of H2O can be obtained?
18 g H2O
If a student manufactures 24.0 moles of CuTe with a percent yield of 75.0%, how many moles of CuTe could the student have theoretically obtained?
32.0 mol CuTe
What is the mass percent of nitrogen in NH4NO3?
35% by mass
What is the empirical formula of a compound that is composed of 3 g C, 1 g H, and 16 g S?
CH4S2
Balance the following reaction:
Zn + H2SO4 → ZnSO4 + H2O + H2S
4 Zn + 5 H2SO4 → 4 ZnSO4 + 4 H2O + H2S
N2 + 3 H2 → 2 NH3
If 56 g N2 react with 18 g H2, what mass of NH3 is obtainable?
68 g NH3
If an experiment has a ‒40.% error in producing 36 grams of kryptonite, what is the theoretical yield?
60. g kryptonite
(Kr is not kryptonite!)