Answer
There is necessary a total of $0.50$ mole of $C_2H_2$ to produce 0.50 mole of $H_2O$.
Work Step by Step
1. Find the mole-mole conversion factors:
According to the coefficients: 2 moles $H_2O$ = 2 moles $C_2H_2$
$\frac{ 2 \space moles \space H_2O}{ 2 \space moles \space C_2H_2}$ and $\frac{ 2 \space moles \space C_2H_2}{ 2 \space moles \space H_2O}$
2. Use the mole-mole conversion factors to calculate the amount of equivalent $C_2H_2$ in moles:
$ 0.50$ mole $H_2O \times \frac{ 2 \space moles \space C_2H_2}{ 2 \space moles \space H_2O} = 0.50$ mole $C_2H_2$
