Question

A solution having pH of 6.0 is how much more acidic than a similar solution of pH of 7.0?

• A. 2 times
• B. 5 times
• C. 10 times
• D. 15 times

Hint:

Each 1-unit decrease in pH represents a 10-fold ($10\times$) increase in acidity ($[\text{H}^+]$ concentration). 2 units $\implies 100\times$.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The Sørensen pH scale is a negative logarithmic scale of hydronium/hydrogen ion concentration in aqueous solutions.
Key Formula or Approach:
\[ \text{pH} = -\log_{10}[\text{H}^+] \implies [\text{H}^+] = 10^{-\text{pH}} \]

Step 2: Detailed Explanation:
For solution 1 with \(\text{pH} = 6.0\):
\[ [\text{H}^+]_1 = 10^{-6}\text{ moles/L} \]
For solution 2 with \(\text{pH} = 7.0\) (neutral):
\[ [\text{H}^+]_2 = 10^{-7}\text{ moles/L} \]
Taking the ratio of hydrogen ion concentrations:
\[ \frac{[\text{H}^+]_1}{[\text{H}^+]_2} = \frac{10^{-6}}{10^{-7}} = 10^1 = 10 \]
Thus, a solution of pH 6.0 contains 10 times higher hydrogen ion activity and is 10 times more acidic than a solution of pH 7.0.

Step 3: Final Answer:
Therefore, the solution of pH 6.0 is 10 times more acidic, corresponding to option (C).