Category: Chemical Engineering Math
"Published in Newark, California, USA"
A common laboratory preparation of oxygen gas is the thermal decomposition of potassium chlorate over MnO2 catalyst. Assuming complete decomposition, calculate the number of grams of oxygen gas that can be obtained from 45.7 grams of potassium chlorate.
Solution:
Consider the decomposition of potassium chlorate as follows
The number of moles of KClO3 is
The number of moles of O2 is
Therefore, the amount of oxygen gas obtained from the decomposition of KClO3 is
Category: Chemical Engineering Math
"Published in Newark, California, USA"
A 10 L vessel containing 8.00 grams of O2 is connected by means of a valve to a 5 L vessel containing 7.00 grams of N2. When the valve was opened and the gases are allowed to mix, what will be the total pressure of the gas mixture at 25°C assuming the temperature was kept constant?
Solution:
The first thing that we need to do is to get the number of moles of O2 and N2.
The number of moles of O2 is
The number of moles of N2 is
The absolute temperature of the gas mixture is
The universal gas law constant for L, gmole, K, and atm is
.
The partial pressure of O2 at the gas mixture is
The partial pressure of N2 at the gas mixture is
Therefore, the total pressure of the gas mixture is
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.
