Answer to Question #140744 in Inorganic Chemistry for Iyana Penelope Gardose

Question

solve for the pH of a solution containing 7.5g of ammonium hydroxide in 1.5L soln. Kb of ammonium hydroxide is 4.8x10^-11

Answer 1

M(NH₄OH) = 35 g/mol

n(NH₄OH) = m/M = 7.5 g / 35 g/mol = 0.214 mol

C(NH₄OH) = n/V = 0.214 mol / 1.5 L = 0.143 mol/L

NH₄OH = NH₄⁺ + OH^-

0.143 M 0 0

-x +x +x

0.143-x x x

K_b = 4.8x10^-11 = (x)(x) / 0.143 - x = x² / 0.143

x = 2.6x10^-6 M

pH = -lg [OH^-] = -lg (2.6x10^-6) = 5.585