1. Aim # 11: What do the coefficients of a chemical equation represent?
H.W. # 11
Study pp (sec. 9.1 and 9.2)
Study class notes
Complete handout sheet

2. 3H2(g) + N2(g) → 2NH3(g)
How many molecules of hydrogen gas would be needed to react completely with 1 molecule of nitrogen to produce
2 molecules of ammonia?

3. + → How many molecules of H2 gas would→
How many molecules of H2 gas would
be needed to react completely with
6 molecules of N2 gas?
with 6.02 x 1023 molecules of N2 gas?
How many moles of H2 gas would be needed to
react with 1 mole of N2 gas?

4. Note: Each substance in the reaction is a gas.
If the reaction were carried out at STP, what would be the volumes of the gases if the coefficients in the equation represented numbers of moles?
What are the ratios of the volumes?

5. I The coefficients of a balanced chemical equation can represent 3 things regarding the quantities of reactants and products.
1. The relative number of particles (atoms or molecules).
2. The relative number of moles.
3. The relative volumes of gases when
all the gases are at the same temperature and pressure.

6. II Mole Problems
1. The balanced equation for the reaction
of hydrogen sulfide with oxygen is
2H2S(g) + 3O2(g) → 2SO2(g) + 2H2(g)
How many moles of SO2(g) are produced by the reaction of 6 moles of O2(g) with sufficient H2S(g)?

7. Ans. 6 mol O2 x 2 mol SO2 = 4 mol SO2 3 mol O2
Note: the conversion factor comes from a ratio.
2 mol SO2 = x mol SO2
3 mol O mol O2

8. 3. Given the following balanced equation
2. How many moles of water will be produced when 1.5 moles of CH4(g) reacts completely?
Ans: 1.5 mol CH4 x 2 mol H2O
1 mol CH4
= 3.0 mol H2O
3. Given the following balanced equation
2Ch3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(l)
How many moles of oxygen will be needed to
react completely with 2.5 mole of CH3OH?

9. Ans: 100 ml O2 x 1ml C3H8 = 20 mL C3H8 5 ml O2
100 ml O2 x 3 ml CO2 = 60 ml CO2
5 ml O2

10. Ans: 2.5 mol CH3OH x 3 mol O2 = 3.8 mol O2 2 mol CH3OH
III Particle Problems
1. For the reaction
P2O H2O → 2H3PO4
How many molecules of H2O would be
needed to react with enough P2O5 to
produce 6.00 x 1020 molecules of H3PO4?

11. Ans: 6.00 x 1020 molecules x 3 molecules H2O H3PO4 2 molecules H3PO4 = 9.00 x 1020 molecules H2O
2. For the reaction
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
How many molecules of HCl would react with
5.0 x 105 molecules of zinc to produce zinc
chloride and hydrogen?

12. Ans: 5. 0 x 105 atoms Zn x 2 molecules HCl 1 atom Zn = 10
Ans: 5.0 x 105 atoms Zn x 2 molecules HCl atom Zn = 10. x 105 molecules HCl = 1.0 x 106 molecules HCl
IV Volume Problems
1. For the reaction
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
What volume of propane (C3H8) will react
with 100 mL of oxygen to form carbon dioxide
and water vapor?
What volume of CO2 would be produced?