Category: Chemical Engineering Math
"Published in Newark, California, USA"
A sample of pure zinc metal reacts completely with an excess of hydrochloric acid. The hydrogen gas produced is collected over water at 25°C and 1 atm. If the metal weighs 253.02 mg, how much hydrogen gas is collected?
Solution:
Consider the chemical reaction of pure zinc metal with hydrochloric acid to form hydrogen gas collected over water as follows
From the chemical reaction above, the number of moles of hydrogen gas collected over water is
The absolute temperature of oxygen gas is
The universal gas law constant for mL, mgmole, K, and atm is 
.
Therefore, by Ideal Gas Law, the amount of hydrogen gas collected over water
Category: Chemical Engineering Math
"Published in Newark, California, USA"
How many grams of KClO3 are needed to prepare 1.8 L of O2 gas that is collected over H2O at 22°C and 760 torr? Vapor pressure of water at 22°C is 19.8 torr.
Solution:
From the given word problem, it is about Dalton's Law of Partial Pressure because it involves the mixture of gas vapors. In this problem, oxygen gas that is collected from the decomposition of KClO3 over water is not a pure oxygen. It is a mixture of pure oxygen and water vapor. By Dalton's Law of Partial Pressure, the pressure of pure oxygen is
The absolute temperature of oxygen gas is
The universal gas law constant for gmole, K, and mm Hg (torr) is 
.
By Ideal Gas Law, we can calculate the number of moles of oxygen gas as follows
From the decomposition of KClO3 by heating,
Therefore, the amount of KClO3 is
