A solution of HCl with a concentration of 4×10 mol L has a pH value of

Question

ScanSolve AI Tutor · Accepted Answer

Here's the solution for question 3:

3. The question asks for the pH of an HCl solution with a concentration of $4 \times 10^{-4}$ mol L $^{-1}$ .

Determine the concentration of hydrogen ions.
HCl is a strong acid, meaning it dissociates completely in water. Therefore, the concentration of H $^+$ ions is equal to the concentration of HCl.
$[\text{H}^+] = 4 \times 10^{-4} \text{ mol L}^{-1}$
Calculate the pH using the formula $\text{pH} = -\log[\text{H}^+]$ .
$\text{pH} = -\log(4 \times 10^{-4})$ $\text{pH} = -(\log 4 + \log 10^{-4})$ $\text{pH} = -(0.602 - 4)$ $\text{pH} = -(-3.398)$ $\text{pH} = 3.398$
Rounding to two decimal places, the pH is approximately 3.40.

Comparing this to the given options, (c) 3.21 is the closest value.

The correct option is (c) $\boxed{\text{3.21}}$ .

Answer