$v_{rms} = \large \sqrt \frac{3k_BT}{M}$, where $k_B$ is the Boltzman's constant and M is the molar mass of the gas and T is the temperature.

$v_{rms} CO_2 = \large \sqrt \frac{3k_BT_1}{44}$

$v_{sound} = \large \sqrt \frac{\gamma k_BT}{M}$, where $k_B$ is the Boltzman's constant and M is the molar mass of the gas, $\gamma$ is the adiabatic index and T is the temperature.

$v_{sound}H_2 = \large \sqrt \frac{7 k_BT_0}{5M}$

$2 \times v_{sound} H_2 = v_{rms} CO_2 \rightarrow 2 \large \sqrt \frac{7k_B\times T_0}{5\times2.01} $$= \large \sqrt \frac{3k_BT_1}{44}$

$T_1 = \large\frac{4 \times 7\times T_0 \times 44}{5 \times 2 } $$\approx 41 T_0$