Question

Calculate the ph of a solution formed by mixing 250. 0 ml of 0. 15 m nh4cl with 200. 0 ml of 0. 12 m nh3. the kb for nh3 is 1. 8 × 10-5.
i. 9. 45
ii. 4. 74
iii. 9. 06
iv. 04. 55
v. 9. 26

Answer 1

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.

What is pH?

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:

brainly.com/question/14790520

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