Chapter 10.2, Problem 32LC

Interpretation Introduction

Interpretation: The mass of the given collected gas should be calculated and the reason for the importance of mol for this calculation needs to be explained.

Concept Introduction: A factor that uses one set of units to change it to another set of units is said to be a conversion factor.

Explanation of Solution

Given information:

Chemist collects 2.94 L of carbon monoxide gas at STP.

The molar volume of any compound at STP is 22.4 L for 1 mol of the compound.

  $\text{22}\text{.4 L = 1 mol}$

In the given information, carbon monoxide, $\text{CO}$ gas is considered an ideal gas. So, the number of moles can be determined using the following conversion factor:

  $\frac{\text{1 mol}}{\text{22}\text{.4 L}}\times 2.94\text{ L}$

So,

  $\frac{\text{1 mol}}{\text{22}\text{.4 L}}\times 2.94\text{ L = 0}\text{.13 mol}$

Now, the mass of the gas can be calculated using the number of moles and molar mass of gas as:

  $\text{mass = moles }\times \text{ molar mass}$

Substituting the values as:

  $\begin{array}{l}\text{mass = 0}\text{.13 mol }\times \text{ 28 g/mol}\\ \text{mass = 3}\text{.6 g}\end{array}$

Since the number of moles is intermediate for the determination of the mass of the gas, so, it is important to calculate the number of moles of the gas.