Here, we have to find out the temperature at which the rms speed of the hydrogen molecules doubles at NTP. According to the the kinetic theory gases the rms speed of molecules of a gas is given by crms = √
3RT
M
where R - universal gas constant T - temperature of the gas M - mass of the gas At NTP c0 = √
3RT0
M
When crms becomes twice of that at NTP crms = 2c0 = 2√
3RT0
M
√
3RT
M
= 2√
3RT.
M
√T = 2√T0 T = 4T0 = 4 × 273 = 1092 K That is when temperature T = 1092 K , the rms speed of molecules of hydrogen is twice that at NTP