Ideal Gas Law Problems, 4

Category: Chemical Engineering Math

"Published in Vacaville, California, USA"

A quantity of 280.7 grams of a hydrate, Na₂CO₃•xH₂O was heated in an oven to drive off water. If the steam produced in a 5L vessel at 110ºC exerted a pressure of 39.6 atm, what is the formula of the hydrate?

Solution:

The first thing that we have to do is to get the amount of steam or water by Ideal Gas Law as follows

The absolute temperature of a gas is  

The universal gas law constant for L, gmole, K, and atm is .  

Hence, the number of moles of water vapor is

The weight of water vapor is

The weight of Na₂CO₃ in Na₂CO₃•xH₂O is

The number of moles of water in Na₂CO₃•xH₂O is

The number of water molecules in Na₂CO₃•xH₂O is

Therefore, the molecular formula of the hydrate is Na₂CO₃•4H₂O.