Answer :
Percentage yield = (actual yield / theoretical
yield) x 100%
The balanced equation for the reaction is,
CH₄(g) + Cl₂(g) → CH₃Cl(g)
+ HCl(g)
Since there is excess of Cl₂ gas, we can assume that all of CH₄ gas are reacted.
Moles of CH₄(g) = mass / molar mass
= 25.0 g / 16 g/mol
= 1.5625 mol
The stoichiometric ratio between CH₄(g) and CH₃Cl(g)
is 1 : 1
Hence moles of CH₃Cl(g) = 1.5625 mol
Molar mass of CH₃Cl(g) = 50.5 g/mol
Mass of CH₃Cl(g) = number of moles x molar mass
= 1.5625 mol x 50.5 g/mol
= 78.9 g
Hence theoretical yield = 78.9 g
Actual yield = 45.0 g
Hence,
Percentage yield = (45.0 g / 78.9 g) x 100%
= 57.03%