Free Charles's Law MCQs with Answers

1. A gas at 27 degrees C is heated at constant pressure until its volume doubles. Its final temperature is

• A. 54 degrees C
• B. 300 degrees C
• C. 327 degrees C
• D. 600 degrees C

Explanation: Charles's law must be applied in kelvin, so the initial temperature is 27 plus 273, which is 300 K. Doubling the volume doubles the absolute temperature to 600 K, and converting back gives 600 minus 273, which is 327 degrees Celsius. Doubling 27 to get 54 is the standard mistake and comes from using Celsius directly.

2. Charles's law states that at constant pressure the volume of a fixed mass of gas is

• A. inversely proportional to the absolute temperature
• B. directly proportional to the absolute temperature
• C. independent of temperature
• D. proportional to the square of the temperature

Explanation: Volume rises in direct proportion to absolute temperature, so a graph of V against T in kelvin is a straight line that extrapolates back to the origin. Using degrees Celsius breaks the proportionality entirely, which is why the temperature must always be converted. This is the law behind a hot air balloon.

3. A gas occupies 300 cm3 at 27 degrees Celsius. At constant pressure, what volume will it occupy at 127 degrees Celsius?

• A. 400 cm3
• B. 1411 cm3
• C. 200 cm3
• D. 600 cm3

Explanation: Converting to kelvin gives 300 K and 400 K, and the volume scales in the same ratio, so 300 multiplied by 400 divided by 300 gives 400 cm3. Using Celsius directly would give the wrong ratio of 127 over 27 and the absurd second option. Absolute temperature is non negotiable in every gas law calculation.