Question

You have a certain mass of helium gas (He) in a rigid steel container. You add the same mass of neon gas (Ne) to this container. Which of the following best describes what happens? Assume the temperature is constant.

a) The pressure in the container doubles.

b) The pressure in the container more than doubles.

c) The volume of the container doubles.

d) The volume of the container more than doubles.

e) The pressure in the container increases but does not double.

Answer 1

Correct answer is option e) The pressure in the container increases but does not double.

Explanation:

Ne gas is added to a rigid steel container containing He. Hence, volume is constant as container is rigid made up of steel. Therefore, options c) and d) are not correct.

According to gas law, PV = nRT, at constant V and T, pressure depends upon n i.e. number of moles. Molar mass of Ne (20.0g/mol) is five times larger than that of He (4.0g/mol). Thus, mass of Ne equal to mass of He will contain less number of moles of Ne as compared with that of He. Therefore, number of moles of gas in rigid container increases but does get doubled. Thus, pressure in the container increases but does not double. Hence, correct option is e).