At which temperature will the speed of sound in hydrogen be the same as the speed of sound in oxygen at $100\,^{\circ}C$?

The plot that depicts the behavior of the mean free time $t$ (time between two successive collisions) for the molecules of an ideal gas,as a function of temperature $(T)$,qualitatively,is (Graphs are schematic and not drawn to scale)

From the following $V-T$ diagram,we can conclude that:

$A$ vessel contains $14 \, g$ ($7$ moles) of hydrogen and $96 \, g$ ($3$ moles) of oxygen at $STP$. $A$ chemical reaction is induced by passing an electric spark in the vessel until one of the gases is consumed. The temperature is brought back to its starting value of $273 \, K$. The pressure in the vessel is ...... $atm$.

The ratio of two specific heats of gas ${C_p}/{C_v}$ for argon is $1.6$ and for hydrogen is $1.4$. Adiabatic elasticity of argon at pressure $P$ is $E$. Adiabatic elasticity of hydrogen will also be equal to $E$ at the pressure

$A$ closed compartment containing gas is moving with some acceleration in a horizontal direction. Neglect the effect of gravity. Then the pressure in the compartment is