What is the concentration of H+ ions in moles per dm^3 of a solution of pH 4.398?

What is the concentration of H+ ions in moles per dm^3 of a solution of pH 4.398?

A. 4.0*10^-5

B.  0.4*10^-5 

C. 4.0*10^-3

D. 0.4*10^-3

Calculation:

We use the pH definition:

pH = -log_{10}[H^+]

---

Step 1: Write the expression for H^+

H^+ = 10^{-{pH}} = 10^{-4.398}

Step 2: Evaluate

10^{-4.398} = 10^{-4} * 10^{-0.398}

10^{-0.398} = 0.4

So,
[H^+] = 0.4 *10^{-4} = 4.0 * 10^{-5}  mol dm^{-3}

---

✅ Correct Answer

A. 4.0 * 10^{-5}

QUESTION NUMBER 20