Chemistry

Chemistry

Problem

The average speed at T_1 K and the most probable speed at T_2 K of CO2 gas is 9 \times 10^4 cm sec-1. Calculate the value of T_1 and T_2 . (IIT 1990)
Intuitive explanation

The key is recognizing that average speed and most probable speed follow different formulas from kinetic theory, both depending on temperature and molar mass. Since you're given that these two speeds are equal despite occurring at different temperatures, you can set up two equations using vˉ=8RTπM\bar{v} = \sqrt{\frac{8RT}{\pi M}} and vp=2RTMv_p = \sqrt{\frac{2RT}{M}}, then solve the ratio to find how T1T_1 and T2T_2 relate before plugging in the given speed value.

Intuitive explanation

The key is recognizing that average speed and most probable speed follow different formulas from kinetic theory, both depending on temperature and molar mass. Since you're given that these two speeds are equal despite occurring at different temperatures, you can set up two equations using vˉ=8RTπM\bar{v} = \sqrt{\frac{8RT}{\pi M}} and vp=2RTMv_p = \sqrt{\frac{2RT}{M}}, then solve the ratio to find how T1T_1 and T2T_2 relate before plugging in the given speed value.

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