Equal volumes of 0.20 M ammonium hydroxide and 0.02 M ammonium chloride solutions are mixed together. What will be the pH of the resulting solution? [Given: pK _ b of NH ₄ OH = 4.75 ]

Step-by-step solution

The mixture of a weak base ( NH ₄ OH ) and its salt with a strong acid ( NH ₄ Cl ) forms a basic buffer. According to the Henderson-Hasselbalch equation for a basic buffer: pOH = pK _ b + [ salt ] [ base ] Since equal volumes of the two solutions are mixed, the ratio of their concentrations in the mixture is equal to the ratio of their initial molarities. [ salt ] = 0.02 M [ base ] = 0.20 M pOH = 4.75 + ( 0.02 0.20 ) pOH = 4.75 + (0.1) pOH = 4.75 - 1 = 3.75 The question asks for the pH of the solution: pH = 14 - pO