Chemistry - Molar Ratio Practice Problems
Name: _______________________
Period: ______
1.) N2 + 3 H2 ---> 2 NH3
Write the molar ratios for N2 to H2 and H2 to NH3.
1 mole N2 or 3 moles H2
3 moles H2
1 mole N2
3 moles H2 or 2 moles NH3
2 moles NH3
3 moles H2
A. How many moles of NH3 will be produced from 6.0 moles of Hydrogen gas (and excess Nitrogen
gas)?
6.0 moles H2 2 moles NH3
3 moles H2
= 4 moles NH3
2.) 2 SO2 + O2 ---> 2 SO3
Write the molar ratios for O2 to SO3 and O2 to SO2.
A.) How many moles of Oxygen gas are needed (with excess SO2 ) to produce 10 moles of SO3 gas?
B.) How many moles of SO3 will be produced form 2.5 moles of SO2 in part B?
C.) How many moles of oxygen gas are needed to exactly use up 2.5 moles of SO2?
3.) PCl3 + Cl2 ---> PCl5
Write the molar ratios for PCl3 to Cl2 and PCl3 to PCl5.
A.) How many moles of PCl5 will be produced from 2.0 moles of PCl3 (and excess chlorine gas)?
B.) How many moles of PCl5 can be produced from 10.0 moles of Cl2 (and excess PCl3).
4.) 4 NH3 + 3 O2 ---> 2 N2 + 6 H2O
Write the molar ratios for NH3 to N2 and H2O to N2.
A.) How many moles of ammonia gas are needed (with excess O2 gas) to make 0.5 moles of Nitrogen gas ?
B.) If 24 moles of the product water are produced with sufficient oxygen and ammonia, (NH3),
starting materials, how much nitrogen gas will also be produced?
5.) Fe2O3 + 3 CO ---> 2 Fe + 3 CO2
Write the molar ratios for CO to CO2 and Fe to CO.
A.) How many moles of carbon monoxide gas are needed with excess Fe2O3 gas to make 50 moles of Fe?
B.) If exactly 15 moles of Fe metal are produced during the reaction, and all of the reactants
were used up by the end of the reaction, how many moles of CO were present when
before the reaction started.
6.) Given the UNBALANCED reaction: ___Pb(s) + ___HCl(l)  ___PbCl2(s) + ___H2 (g) How
many moles of HCl are required to completely react with 0.36 moles of lead?
7.) Given the UNBALANCED reaction ___ P(s) + ___Br2(l) ___PBr3(s). How many moles of
Phosphorus tribromide will be produced if 0.78 moles of bromine reacted.
8.) Given the UNBALANCED reaction ___ H2(g) + ___O2(g) ___H2O(l).
hydrogen gas are required to react with 10.0 moles of oxygen gas.
How many moles of
9.) Iron metal reacts with oxygen gas to create iron (III) oxide (Fe2O3). Write the balanced reaction.
How many moles of Iron (III) oxide are created from 0.20 moles of iron metal.
10.)Given the UNBALANCED reaction ___C2H2 (g) + ___O2(g)  ___CO2 + ___H2O burns with
oxygen in a combustion reaction. How many moles of carbon dioxide are produced if 16 moles
of oxygen are consumed burning excess acetylene?
11.)In problem 10, How many grams of acetylene (C2H2) are required to create 36.04 grams of water?