Question

A solution is prepared at that is initially in ammonia , a weak base with , and in ammonium bromide . Calculate the pH of the solution. Round your answer to decimal places.

Answer 1

The question is incomplete, here is the complete question:

A solution is prepared at 25°C that is initially 0.22 M in ammonia $(NH_3)$, a weak base with $K_b=1.8\times 10^{-5}$, and 0.073 M in ammonium chloride $(NH_4Cl$. Calculate the pH of the solution. Round your answer to 2 decimal places.

Answer: The pH of the solution is 9.74

Explanation:

The chemical equation for the reaction of ammonia with hydrochloric acid follows:

$NH_3+HCl\rightarrow NH_4Cl$

To calculate the pOH of basic buffer, we use the equation given by Henderson Hasselbalch:

$pOH=pK_b+\log(\frac{[salt]}{[base]})$

$pOH=pK_b+\log(\frac{[NH_4Cl]}{[NH_3]})$

We are given:

$pK_b$ = negative logarithm of base dissociation constant of ammonia = 4.74

$[NH_4Cl]=0.073M$

$[NH_3]=0.22M$

pOH = ?

Putting values in above equation, we get:

$pOH=4.74+\log(\frac{0.073}{0.22})\\\\pOH=4.26$

To calculate pH of the solution, we use the equation:

$pH+pOH=14\\\\pH=14-4.26=9.74$

Hence, the pH of the solution is 9.74