Consider the balanced equation below. PC13+ Cl2 → PC15
What is the mole ratio of PCI3to PCI5?
1:1
2:1
3:5
5:3

Mole ratio is 1:1

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.

the answer is d.) potassium