Question

Which of the following gases will have the highest velocity at a given temperature?

Answer 1

The velocity of the gas is inversely proportional to the square root of the molar mass of the gass. Heavier molecules tend to travel slow compared to light molecules. Among these, He has the lowest molar mass of 4 g/mol hence this element has the greatest velocity among all molecules given.

Answer 2

Answer:

C. He

Explanation:

The velocity of a gas can be calculated by the equation:

$v = \sqrt{\frac{3RT}{M} }$

Where R is the gas constant, T is the temperature, and M the molar mass of the gas.

At a given temperature, the velocity is  inversely proportional to the square of the molar mass, so as low is the molar mass, as higher is the velocity. The molar masses are:

Ne = 10 g/mol

O₂ = 2*16 = 32 g/mol

He = 4 g/mol

Cl₂ = 2*35.5 = 71 g/mol

Then, He has the lower molar mass and the highest velocity.