【Daily Question】Theoretical Foundation 2020.07.25
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Multiple-choice question: Given that Kθb(NH3) = 1.77×10^-5, when a 0.2 molL-1 solution of NH3.H2O and a 0.2 molL-1 solution of HCl are mixed in equal volumes, what is the pH value of the resulting solution? A、5.12 B、8.87 C、1.63 D、9.73 Answer: A Hint: Extra rewards will be given to those who can explain the solution process; the answer can be found in the response
At the same molar concentration, when two acids or bases of equal mass are mixed, they react completely. The ammonium chloride that is formed is a salt of a strong acid and a weak base; therefore, option bd can be ruled out. The pH value for option c is around 1, which seems quite unreasonable. So I think the correct answer is a (it’s just a guess – please don’t take it seriously)