What minimum volume of hydrogen gas (at STP) is required to fully hydrogenate 15.5 kg of propyne?
The balanced chemical equation for the hydrogenation of propyne is
Like with any stoichiometry problem, the key tool you have at your disposal is the mole ratio.
However, an interesting thing takes place when you're dealing with gases that are under the same conditions for pressure and temperature. In such cases, the mole ratio becomes the volume ratio.
The idea is that, since you're dealing with two ideal gases, you can use the ideal gas law equation to write
P⋅V1=n1⋅RT → for ethyne;
P⋅V2=n2⋅RT → for hydrogen.
The pressure and the temperature are the same for both gases, since the reaction presumably takes place at STP.
If you divided these two equations, you'll get
This is equivalent to
The mole ratio is equivalent to the volume ratio.