Question

If a solution turns red litmus blue, its pH is likely to be:

• A. 1
• B. 4
• C. 5
• D. 10

Answer 1

The correct option is D 10

pH is a measure of the amount of activity of hydrogen ions (${\text{H}}^{+}$) in a solution and thus, its alkalinity or acidity.
pH is described as “the negative of the logarithm of the molar hydronium-ion concentration.”
A neutral solution has pH 7. Acidic substances have pH less than 7. The alkaline (basic) substances have pH more than 7.
A basic solution turns red litmus to blue, which means the solution must have value more than 7.