Question 5.11: The combustion of acetylene with pure oxygen produces a very...
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?
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