Question

Estimate the average thermal energy of a helium atom at (i) room temperature (27 °C), (ii) the temperature on the surface of the Sun (6000 K), (iii) the temperature of 10 million Kelvin (the typical core temperature in the case of a star).​

Answer 1

Solution:

All the three vessels have the same capacity, they have the same volume.

Hence, each gas has the same pressure, volume, and temperature.

According to Avogadro’s law, the three vessels will contain an equal number of the respective molecules. This number is equal to Avogadro’s number, N = 6.023 × 1023.

The root mean square speed (vrms) of a gas of mass m, and temperature T, is given by the relation:

vrms = (3kT/m)1/2

where,

k is Boltzmann constant

For the given gases, k and T are constants.

Hence vrms depends only on the mass of the atoms, i.e.,

vrms ∝ (1/m)1/2

Therefore, the root mean square speed of the molecules in the three cases is not the same. Among neon, chlorine, and uranium hexafluoride, the mass of neon is the smallest. Hence, neon has the largest root mean square speed among the given gases.

Answer 2

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Refer the attachment.