Question

C3H8 + O2 → CO2 + H2O

In the UNBALANCED chemical reaction for the combustion of propane, determine, at standard temperature and pressure, how many liters of carbon dioxide gas are produced if 15 liters of oxygen gas are completely consumed.

A) 3

B) 5

C) 6

D) 9

Answer 1

Answer: 9

Explanation: 9 liters of carbon dioxide gas are produced. The reaction balances with coefficients of 1, 5, 3 and 4. The ratio of moles of oxygen to carbon dioxide is 5:3. At the same temperature and pressure, moles and liters are proportional. So if 15 liters are consumed, at a

5

3

ratio, 9 liters would be produced.

Answer 2

First, we'll balance the equation
C3H8 + 5O2 --> 3CO2 + 4H2O
Next, we know that a gas at stp occupies 22.4 liters/mole, so we can find the number of moles of oxygen gas.
15 liters O2 * (1 mole O2)/(22.4 liters O2) = 0.67 moles O2
Now we know from our balanced equation that there are 3 moles of CO2 per mole of O2, so we can find the number of moles of CO2 we produce.
0.67 moles O2 * (3 moles CO2/5 moles O2) = 0.40 moles CO2
Now, we have the number of moles of CO2, and we know that one mole occupies 22.4 liters, we can find the number of liters
.40 moles CO2 * (22.4 liters CO2)/(1 mole CO2) = 9.0 liters of CO2
The answer is D