Question

The mean kinetic energy of a gas molecule at 27${}^o$C is 6.21 $\times$ 10${}^{-21}$ Joule. Its value at 227${}^o$ C will be

• A. $12.35\times {10}^{-21}Joule$
• B. $11.35\times {10}^{-21}Joule$
• C. $10.35\times {10}^{-21}Joule$
• D. $9.35\times {10}^{-21}Joule$

Answer 1

The correct option is C $10.35\times {10}^{-21}Joule$

Mean KE=$\frac{3kT}{2}$

so $6.21\times {10}^{-21}=3k\times 300/2$

so $k=1.38\times {10}^{-23}$

KE at 500 K ,$KE=3\times 1.38\times {10}^{-23}\times 500/2=10.35\times {10}^{-21}Joule$