Question

A decrease of one unit in the pH scale above represents a tenfold increase in the hydrogen ion concentration of a solution. For example, a solution having a pH of 4 is 10 times more acidic than a solution with a pH of 5. If acid precipitation rain changes the pH of a pond from 7.5 to 6.5, the level of hydrogen ion has changed by a factor of ________
A) 2.0
B) 10
C) 13.0
D) 100
E) 0.01

Answer 1

Answer:

The level of hydrogen ion has increased by a factor of 10.

Explanation:

We know, $pH=-log[H^{+}]$

where $[H^{+}]$ represents concentration of $H^{+}$ in molarity

Here $(pH)_{final}=6.5$

So, $[H^{+}]_{final}=10^{-6.5}M$

Here $(pH)_{initial}=7.5$

So, $[H^{+}]_{initial}=10^{-7.5}M$

Hence, change in pH = $\frac{[H^{+}]_{final}}{[H^{+}]_{initial}}$  = $\frac{10^{-6.5}M}{10^{-7.5}M}=10$

So, the level of hydrogen ion has increased by a factor of 10.

Option (B) is correct