Question

The average kinetic energy for 5 moles of a ideal
monoatomic gas at 27°C is [NCERT Pg. 148]
(1) 37.4 kJ
(2) 12.5 kJ
(3) 18.7 kJ
(4) 30.2 kJ​

Answer 1

Answer:

18.7

average k.E =3/2nRT

=3/2×5×8.314×300

= 18.7kj

Answer 2

Given :

Number of moles = 5

Temperature (T) = 27°C = (273 + 27)K = 300 K

To Find :

Average Kinetic Energy

Solution :

For a monoatomic ideal gas only translational kinetic energy contributes to the energy. The average translational kinetic energy of a single atom depends only on the gas temperature and is given as -

     Average Kinetic Energy ($K_{avg}$) = $\frac{3}{2} n R T$

(where, R = Molar gas constant; T = Temperature; n = number of moles)

Average Kinetic Energy ($K_{avg}$) = $\frac{3}{2}$×5×8.314×300

                                                   = 18706.5 J

                                                   = 18.7 KJ

∴ The average kinetic energy for 5 moles of an ideal monoatomic gas at 27°C is 18.7 KJ

The correct option is (3) 18.7 KJ