Chemistry 3rd Nine Week Benchmark Study Sheet
1. Relate the law of conservation of mass to chemical equations.
2. Balance chemical equations.
3. Identify reaction types.
4. Predict the products given reactants (with correct formulas).
5. Know the 3 signs of a chemical reaction.
6. Convert moles to mass and mass to moles.
7. Calculate the percent composition of a compound.
8. Determine empirical formula given percent composition; reduce molecular formula to empirical formula.
9. Be able to write mole ratios.
10. Given a balanced chemical equation be able to do mole-to-mole, mole-to-mass/mass-to-mole, and mass-tomass calculations.
11. Calculate percent yield if given actual and theoretical yields.
12. Calculate molecular formula if given empirical formula and formula mass.
Practice problems:
A. State the reaction type, predict the products, then balance the equation.
a) type: __________________________; __ZnS + __HCl 
b) type: __________________________; __Al + __Fe3O4 
c) type: __________________________; __H2 + __Br2 
d) type: __________________________; __C4H10 + __O2 
e) type: __________________________; __Al2O3 
B. Convert as indicated.
a) 3.00 mol H2 = ____________________ g H2
b) 25.0 g CO2 = __________________ mol CO2
c) 18.0 mol Cu = __________________ g Cu
d) 10.0 g Mg = ___________________ mol Mg
C. Calculate the percent composition for the given compound.
a) H3PO4 = ___________% H, ___________% P, ____________% O
b) NH4NO3 = _______________% N, ______________% H, _____________% O
c) NaCl = _______________% Na, ________________% Cl
d) Al2(SO4)3 = _________________% Al, _______________% S, ________________% O
D. Determine the empirical formula from the given information.
a) molecular formula is C6H12O6; empirical formula = _________________
b) molecular formula is CH4; empirical formula = ________________
c) percent composition is 56.0% V, 44.0% O; empirical formula = __________________
d) percent composition is 92.25% C, 7.75 % H; empirical formula = __________________
E. Use the following balanced equation to calculate as indicated: 3Ca(OH)2 + 2H3PO4 Ca3(PO4)2 + 6H2O
a) If you have 12.0 mol of H3PO4, how many moles of water will be produced? ____________________
b) If you have 50.0 g of Ca(OH)2, how many moles of Ca3(PO4)2 will be produced? ____________________
c) If you made 25.0 g of Ca3(PO4)2, how many grams of Ca(OH)2 did you use? ______________________
d) If you made 48.0 mol of water, how many grams of H3PO4 did you use? _______________________
F. Calculate the percent yield.
a) You calculated 155.0 g of product; experiment made 147.8 g of product: _____________% yield
b) You calculated 84.7 g of product; experiment made 59.4 g of product: _____________% yield
G. Calculate the molecular formula. [note that amu = g/mol]
a) Empirical formula is C5H4; formula mass is 128.174 amu; molecular formula = ___________________
b) Empirical formula is PbCl4; formula mass is 349.012 amu; molecular formula = ___________________
c) Empirical formula is C2H4O; formula mass is 88.106 amu; molecular formula = ____________________