Question

Phosphorous Pentachloride reacts with water to form hydrochloric acid and phosphoric acid. How many total moles of acid are formed when starting with 4.5g of PC5 and excess H20.

Answer 1

Given that:

Phosphorous pentachloride reacts with water and form hydrochloric acid and phosphoric acid. The reaction is given as:

PCl₅ + 4H₂O → 5HCl + H₃PO₄

from the above equation it is clear that 1 mole of PCl₅ will produce 6 moles of acid (5 moles HCl and 1 mole H₃PO₄).

Gram molecular weight of 1 mole of PCl₅ is 208 g/mol.
Now we have to find the moles of acid formed when 4.5g of PCl₅ reacts with excess water. That can be calculated as:

4.5 g PCl₅ x (1 mole PCl₅ / 208 g PCl₅) x (6 moles acid / 1 mole PCl₅) = 0.129 moles acid

0.129 moles of acid will form when we start the reaction with 4.5g of PCl₅ and excess H₂O.