Question

At 25°C, the following data were collected:
Solution A: pH = 8.46
Solution B: pOH = 9.30
Solution C: [H+] = 2.5 × 10-4 M
Solution D: [OH-] = 1.1 × 10-10 M
Which lists the solutions in order of increasing acidity?
a. C < D < A < B
b. B < A < D < C
c. A < B < D < C
d. A < B < C < D

Answer 1

Answer: A< B< D< C

Explanation:

pH or pOH is the measure of acidity or alkalinity of a solution.

pH is calculated by taking negative logarithm of hydrogen ion concentration.

$pH=-\log [H^+]$

$pOH=-\log[OH^-]$

Lower is the $H^+$ , higher is the acidity.

a. Solution A: pH = 8.46

Putting in the values:

$8.46=-\log [H^+]$

$[H^+]=3.47\times 10^{-9}M$

b. Solution B: pOH = 9.30

$9.30=-\log [OH^-]$

$[OH^-]=5.01\times 10^{-10}M$

$[H^+][OH^-]=10^{-14}$

$[H^+]=\frac{10^{-14}}{5.01\times 10^{-10}}=0.20\times 10^{-4}$

c. Solution C: $[H^+]=2.5\times 10^{-4}$

d. Solution D: $[OH^-]=1.1\times 10^{-10}$

$[H^+][OH^-]=10^{-14}$

$[H^+]=\frac{10^{-14}}[1.1\times 10^{-10}}=0.91\times 10^{-4}$

Thus the order of increasing acidity is A< B< D< C