Question

Ammonia, NH3, is a weak base that is often used in household cleaning solutions. what is the pH of a solution of ammonia that contains 5.0 g of ammonia in 709 mL

Answer 1

Answer:

11.44

Explanation:

$K_b$ = Base ionization constant of ammonia = $1.8\times 10^{-5}$

m = Mass of ammonia = 5 g

V = Volume of ammonia = 709 mL = $709\times 10^{-3}\ \text{L}$

M = Molar mass of ammonia = 17.03 g/mol

Molaritiy of ammonia

$C=\dfrac{n}{V}\\\Rightarrow C=\dfrac{\dfrac{m}{M}}{V}\\\Rightarrow C=\dfrac{\dfrac{5}{17.03}}{709\times 10^{-3}}\\\Rightarrow C=0.414$

We have the relation

$pOH=\dfrac{1}{2}(pK_b-\log C)\\\Rightarrow pOH=\dfrac{1}{2}(-\log (1.8\times 10^{-5})-\log 0.414)\\\Rightarrow pOH=2.56$

$pH+pOH=14\\\Rightarrow pH=14-pOH\\\Rightarrow pH=14-2.56\\\Rightarrow pH=11.44$

The pH of the solution is 11.44.