Question

Hydrogen ion concentration in mol/L in a solution of pH = 5.4 will be:
(A) $3.98 \times {10}^{8}$
(B) $3.88 \times {10}^{6}$
(C) $3.68 \times {10}^{-6}$
(D) $3.98 \times {10}^{-6}$

Answer 1

Hint: The hydrogen ions concentration in a solution refers to the measure of acidity of the substance. This concentration is measured in moles per litre or in pH units.

Complete answer:
The pH of any solution or substance is the measure of how acidic or basic it is. If a substance is as acidic in nature the pH value will be as much low. Similarly, If a substance is as basic in nature the pH value will be as much high. And the higher the concentration of hydrogen ion, the more acidic the solution and the lower the pH. And vice versa goes for basicity.
Now, let us get back to the question given to us. We are provided with the pH value of the solution and we need to find the hydrogen ion concentration. To find the hydrogen ion concentration, we need to use the formula given below:
pH = -log[hydrogen ion concentration]
or, $pH = -log[{H}^{+}]$ ----(1)
In the above formula, the square brackets denote the concentration of hydrogen ions.
Substituting the values in equation (1), we get,
$5.4 = -log[{H}^{+}]$
Now, taking antilog on both sides, we get
$[{H}^{+}] = 3.98 \times {10}^{-6}$ mol/L
Therefore, the hydrogen ion concentration in a solution with pH=5.4is $3.98 \times{10}^{-6}$ mol/L.
Hence, option (d) is the correct answer.

Note: The hydrogen ion concentration is the amount of hydrogen ions present in the water solutions. It exits in water in the form of a combined molecule ${H}^{+}.{H}_{2}O$. This formula ${H}^{+}.{H}_{2}O$ is commonly written as ${H}_{3}{O}^{+}$ and is known as hydronium or as oxonium ion.