Table of contents

7. Gases

The Ideal Gas Law: Density

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Multiple Choice

What is the density of ethane (C2H6) at standard temperature and pressure (STP)?

1.34 g/L

0.98 g/L

1.25 g/L

1.50 g/L

Verified step by step guidance

Start by recalling the definition of standard temperature and pressure (STP), which is 0°C (273.15 K) and 1 atm pressure.

Use the ideal gas law equation:

P V = n R T

, where P is pressure, V is volume, n is moles, R is the ideal gas constant, and T is temperature.

Calculate the molar mass of ethane (C2H6) by adding the atomic masses of carbon and hydrogen:

2 \times 12.01 + 6 \times 1.008

At STP, 1 mole of any gas occupies 22.4 L. Use this information to find the mass of ethane in 22.4 L using its molar mass.

Finally, calculate the density using the formula:

d = \frac{m}{V}

, where m is mass and V is volume. Substitute the mass of ethane and the volume (22.4 L) to find the density.

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