Answer:
0.299 moles of PCl5
Explanation:
First form an equation based of given information: P4 + Cl2= 4PCl5
Next balance it: P4 + 10Cl2 = 4PCl5
Take your given value (53.0g of Cl2) and divide it by its molar mass to get moles of Cl2: 53.0g/70.906g = 0.747 moles Cl2
Then, multiply by the molar ratio (10Cl2 to 4PCl5): (0.747 x 4 mol PCl5)/10 mol Cl2 = 0.299 moles PCl5