The pH of HCl and H_2SO_4 is same at same temperature. What is the...

Let the molar concentration of $\text{HCl}$ be $C_1$ and $\text{H}_2\text{SO}_4$ be $C_2$.

Since $\text{HCl}$ is a strong monoprotic acid, the concentration of hydrogen ions is $[\text{H}^+] = C_1$.

Since $\text{H}_2\text{SO}_4$ is a strong diprotic acid, assuming complete dissociation, the concentration of hydrogen ions is $[\text{H}^+] = 2C_2$.

Given that the pH of both solutions is the same, their $[\text{H}^+]$ must be equal.

$C_1 = 2C_2$

$\dfrac{C_1}{C_2} = \dfrac{2}{1}$

The ratio of molar concentration of $\text{HCl}$ to $\text{H}_2\text{SO}_4$ is $2:1$.

Answer: $2:1$