Answer:
Mole ratio is 1:1
Step-by-step explanation:
The equation is:
PCl₃ + Cl₂ → PCl₅
We see that is correctly balanced.
1 mol of PCl₃ react to 1 mol of chlorine gas in order to produce 1 mol of PCl₅
That's why, the mole ratio is, 1:1
There is not another number than 1, at stoichiometry of reaction.