Carbon dioxide, M = 44.01 g/mol, is heated from 300 K to 450 K…

Step 1. At $300\ \text{K}$. $u_{\text{mp}} = \sqrt{\dfrac{2 \times 8.314 \times 300}{0.04401}} = 336.7\ \text{m/s}$, so $x = \dfrac{800}{336.7} = 2.376$. The fraction is $\text{erfc}(2.376) + \dfrac{2}{\sqrt{\pi}} \times 2.376 \times e^{-5.646} = 0.0008 + 0.0095 = 0.0102$, which is $1.02\%$.

Step 2. At $450\ \text{K}$. $u_{\text{mp}} = 412.3\ \text{m/s}$, so $x = 1.940$. The fraction is $0.0061 + 0.0508 = 0.0568$, which is $5.68\%$.

Step 3. The growth of the fast fraction. $\dfrac{5.68}{1.02} = 5.55$ times, taking the more exact values.

Step 4. The growth of the average speed. $\sqrt{\dfrac{450}{300}} = 1.22$ times.

Step 5. The meaning. A rise of $50\%$ in temperature raises the average speed by only $22\%$. But it raises the number of molecules that are fast enough to react by more than five times. This is why the rate of a reaction is so sensitive to the temperature.