Chemistry
Extra Test Prep Examples
UNIT: Moles, % Comp, EF & MF
1. What is the mass (in grams) of 0.0714 mol of iron (III) sulfate, Fe2(SO4)3?
2. What is the percent composition of the compound (NH4)3P.
3. Vitamin C contains 40.92% C, 4.58% H, and 54.50% O. What is the empirical formula for
vitamin C?
4. A certain compound has an empirical formula of C3H4. If the molar mass of this unknown is
121 grams/mol, what is the molecular formula for this compound?
5. Fred the Chemist is in the lab trying to find the empirical formula of a compound made from
magnesium and chlorine. Use the data below to help out Fred:
Mass of crucible
Mass of crucible + Mg
Mass of crucible + product (Mg + Cl)
Answers on second page
20.00 grams
20.45 grams
21.76 grams
1. Ans: 28.6 grams Fe2(SO4)3
2. Ans: 49.38% N; 14.21% H; 36.40% P
3. Ans: C3H4O3
4. Ans: C9H12
5. Ans: MgCl2