## Chapter 5

## Q. 5.11

## Q. 5.11

The combustion of acetylene with pure oxygen produces a very high-temperature flame used for welding and cutting metals. Calculate the volume of O_{2} (in liters) required for the complete combustion of 7.64 L of acetylene (C_{2}H_{2}) measured at the same temperature and pressure.

2C_{2}H_{2}(g) + 5O_{2}(g) → 4CO_{2}(g) + 2H_{2}O(l)Strategy Note that the temperature and pressure of O_{2} and C_{2}H_{2} are the same. Which gas law do we need to relate the volume of the gases to the moles of gases?

## Step-by-Step

## Verified Solution

According to Avogadro’s law, at the same temperature and pressure, the number of moles of gases is directly related to volume. From the equation, we have 5 mol O_{2} \bumpeq 2 mol C_{2}H_{2} ; therefore, we can also write 5 L O_{2} \bumpeq 2 L C_{2}H_{2} . The volume of O_{2} that will react with 7.64 L C_{2}H_{2} is given by

volume of O_{2}=7.64 \cancel{L C_{2}H_{2}}\times \frac{5 L O_{2}}{2 \cancel{L C_{2}H_{2}}}

=19.1 L