Question

What is the pH of the buffer solution containing 0.1 mol of NH4OH and 0.1 mol of NH4Cl in 1
liter of solution (pK (NH4OH) = 4.75)? How will the pH change when solution would be diluted 10 times?​

Answer 1

Explanation:

equation : NH₄OH --------> NH₄ + OH

pKb = 4.75

so, the formula is pOH = pKb + log [NH₄]/[NH₃]

                                      = 4.75 + log [0.1]/[0.1]

                                      = 4.75

pH = 14 - pOH

     = 14 - 4.75

     = 9.25

for a basic solution, dilution upto 10 times is equal to the initial pH minus 1

so after dilution pH would be 8.25

for an acidic solution, dilution upto 10 times is equal to the initial pH plus 1