Question

Water sample of pH = 4 when compared to sample of pH = 7, will be more acidic by:
1. 3 times
2. 300 times
3. 1000 times
4. None of these

Answer 1

Correct Answer - Option 3 : 1000 times

Concept

We know, pH is defined as the negative logarithm of [H]⁺ ion.

So, 

pH = -log10 [H+]

-log10 [H+] = pH

[H+] = 10 -pH

Calculation

 pH of water samples are 

 pH = 4 ⇒[H⁺] = 10 ^{- 4}

 pH = 7 ⇒ [H+] = 10^-7 

Comparing Both [H⁺]

\(\frac{{{{\left[ {{H^ + }} \right]}_I}}}{{{{\left[ {{H^ + }} \right]}_{II}}}} = \frac{{{{10}^{ -4}}}}{{{{10}^{ - 7}}}} = {10^{3}} = 1000\)

Hence, first sample is 1000 times acidic than second sample.