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Monday, May 4, 2015

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 110ÂșC 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.