Final answer:
The molar mass of a gas with most probable speed twice that of ethene's most probable speed at 25 degrees Celsius is one-fourth the molar mass of ethene.
Step-by-step explanation:
The student has asked for the molar mass of a gas that possesses a most probable speed at 25 degrees Celsius, which is twice that of the most probable speed of ethene gas. Using the kinetic theory of gases, the most probable speed of a gas (vp) is directly proportional to the square root of the temperature and inversely proportional to the square root of the molar mass.
This can be expressed through the formula vp √(T/M), where T is the temperature and M is the molar mass. If the most probable speed of another gas is twice that of ethene, the molar mass of this gas would be inversely proportional to the square of the speed ratio, thus making the molar mass of the unknown gas four times less than that of ethene.
Therefore, the correct answer is: (d) Molar Mass of Ethene/4.