Question

A 1.0L solution contains equimolar amounts of NH4Cl and NH3, 10 mL of water is added to the solution. Which statement describes the effect of the added water use equations to explain

a) pH increases b) pH decreases c) pH remains unchanged d) molar concentration of the NH3 increases

Answer 1

pOH = pKb + log([NH_​​4⁺]/[NH_{​​​​​3}])

Concentration of NH_{​​​​​4}​​​​Cl = NH_{​​​​​3}

That means pOH = pKb

When 10ml water is added to the buffer concentration of ammonium ion and ammonia changes equally . The ratio of their concentration does not change . Hence pH would remains same .

On dilution pH of buffer does not changes

Answer: (c) pH remains unchanged