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Module 1: Basic Concepts - Moles - Practice Problems

 
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Instructions:
Work these problems on a sheet of paper and check your answers against those provided below.

Helpful Calculators:
The following calculators may be useful in solving these problems. You can access them either from the "Calculators" button on the screen or from the links below.

Mole Calculator I
Mole Calculator II

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Q icon #1
There are 450 pounds of oxygen in a compressed air tank. How many pound moles of oxygen are present? How many gram moles are present? Link to periodic table of elements.
A icon
Answer: 6,384 gm moles O2

Solution:
equation 1

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Q icon #2
How many pound moles of oxygen are needed to react with 1,000 pounds of carbon? Assume that all of the oxygen reacts as shown in the following reaction:
equation 2

Link to periodic table of elements.
A icon
Answer: 83.33 pound moles of oxygen

Solution:
  1. Calculate the pound moles of carbon.
    equation 2(1)

  2. Calculate how many pound moles of oxygen are needed.

    From the chemical equation, one pound mole of oxygen is needed for every pound mole of carbon; therefore, 83.33 lb moles of oxygen is needed.

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Q icon #3
What is the average molecular weight of moist air containing 78% nitrogen, 20% oxygen, and 2% water vapor? Link to periodic table of elements.

A icon
Answer: 28.6 lbm/lb mole

Solution:
  1. Calculate molecular weights of each component in the gas stream.
    equation 3(1)

  2. Calculate the weighted average molecular weight for mixture in air stream.
    equation 3(2)

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