Question

When 25 mL of 0.30 M ammonium iodide and 25 mL of 0.30 M sodium hydroxide are combined, the pH of the resulting solution will be : ..... A. Less than 7 B. Equal to 7 C. Greater than 7

Answer 1

pH of the resulting solution is greater than 7

Step-by-step explanation:

Concentration of ammonium iodide = 25 x 0.3 mmol

= 7.5 mmol

And concentration of Sodium hydroxide solution = 25 x 0.3 mmol

= 7.5 mmol

Since the concentration of both solution is equal.

The ionization reaction is

NH₄I + NaOH → NaI + NH₄OH

Concentration of NH₄OH is equal to 7.5 mmol because NH₄OH is the product of above reaction and the two electrolytes are strong, So completely ionized in solution.

so pOH = -log(7.5 x 10⁻³)

= 2.12

We know pH + pOH = 14

pH = 14 - 2.12 = 11.88

Since pH of the solution is greater than 7