Question

The average translational kinetic energy of oxygen molecules at a temperature of $127^\circ\text{C$ is (Boltzmann constant $= 1.38 \times 10^{-23}~\text{J/K}$)}

• A. $4.07 \times 10^{-21}~\text{J}$
• B. $2.07 \times 10^{-21}~\text{J}$
• C. $8.28 \times 10^{-21}~\text{J}$
• D. $8.00 \times 10^{-21}~\text{J}$

Hint:

Use $\dfrac{3}{2}kT$ for average KE per molecule in ideal gas, and always convert temperature to Kelvin.

Answer 1

The Correct Option is C

$T = 127^\circ\text{C} = 400~\text{K}$
Average KE = $\dfrac{3}{2}kT = \dfrac{3}{2} \cdot 1.38 \times 10^{-23} \cdot 400$
$= 1.5 \cdot 1.38 \cdot 400 \times 10^{-23} = 828 \times 10^{-23} = 8.28 \times 10^{-21}~\text{J}$