Question

In which sample is the average kinetic energy of the particles greatest?

(1) 10. mL of HCl(aq) at 25°C
(2) 15 mL of HCl(aq) at 20.°C
(3) 10. mL of H2O(l) at 35°C
(4) 15 mL of H2O(l) at 30.°C

Answer 1

The question asks about the average kinetic energy, so it is related only to temperature. Then the answer is (3) with the highest temperature.

Answer 2

Answer: The correct answer is option 3.

Explanation: Average kinetic energy is defined as the energy of motion of the particles of a system. It is a measure of Kelvin Temperature.

Mathematically,

`K=(3)/(2)(R)/(N_A)T`

where,

K = kinetic energy of the molecules measured in joules.

R = Gas constant =
`8.314Jmol^(-1)K^(-1)`

`N_A` = Avogadro's number =
`6.022* 10^(23)atoms/mol`

T = Temperature in kelvins.

Kinetic energy is directly proportional to the temperature of the system.

`\text{Kinetic energy}\propto \text{Temperature}`

More the temperature, more will be the kinetic energy of the molecules.

Hence, the correct answer is Option 3.