Question

Calculate the pH A sample of seawater that has an OH− concentration of 1.90×10−6 M

Answer 1

Ans. # Step 1: Given-          [OH^-] = 1.90 x 10^-6 M

So, pOH = -log [OH^-] = - log (1.90 x 10^-6) = 5.72

# Step 2: Use            pH + pOH = 14.00               - equation 1

Putting the value of pOH in equation 1-

pH = 14.00 – pOH = 14.00 - 5.72 = 8.28

Hence, pH = 8.28

# Method 2: Use      [H⁺] [OH^-] = 10^-14     - equation 2

So,

            [H⁺] = 10^-14 / (1.90 x 10^-6) = 5.2632 x 10^-9 M

Now, pH = -log [H⁺] = -log (5.2632 x 10^-9) = 8.28