The potential of the hydrogen in water gives the pH of the acidity and basicity of the solution. The pH of the solution is 9.06. Thus, option iii is correct.
<h3>What is pH?</h3>
The pH of a substance is given by the subtraction of the pOH from 14 which is the range of the pH scale.
The dissociation reaction for ammonia is given as,
NH₃ (aq) + H₂O (l) ⇄ NH₄⁺ (aq) + OH⁻ (aq)
Here, the concentration of ammonia is [NH₃] - x, ammonium ion is [NH₄⁺] + x, and hydroxide ion is x.
The molar concentration of ammonia is,
M = (0.12 M × 0.2 L) ÷ 0.45 L = 0.053 M
The molar concentration of ammonium ion is,
M = (0.15 M × 0.25 L) ÷ 0.45 L = 0.083 M
From the base dissociation constant and previous concentration from the reaction, the value of x or hydroxide ion is calculated as,
Kb = [NH₄⁺][OH⁻] ÷ [NH₃]
1.8 × 10⁻⁵ (0.053 - x) - (0.083 + x) × x = 0
x = [OH⁻] = 1.15 x 10⁻⁵
The pH from the hydroxide ion is calculated as,
pOH = - log [OH⁻]
= - log (1.15 x 10⁻⁵)
= 4.94
Further,
pH = 14 - pOH
= 14 - 4.94
= 9.06
Therefore, option iii. 9.06 is the pH of the solution.
Learn more about pH here:
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