Final answer:
The pH of the aqueous solution of the salt BA, formed from a weak acid with a pKa of 4.80 and a weak base with a pKb of 4.78, will be just above 7, with the closest answer being 7.01.option A is correct answer.
Step-by-step explanation:
The subject of this question is acid-base chemistry, which is a fundamental concept in chemistry, particularly when discussing the pH of solutions. We are given the pKa of a weak acid and the pKb of a weak base and asked to find the pH of the corresponding salt, BA, in aqueous solution.
To solve this, let's recall that the pKa and pKb values are related to the acid dissociation constant (Ka) and base dissociation constant (Kb), respectively. For conjugate acid-base pairs, the relationship Ka x Kb = Kw holds true, where Kw is the ionic product of water (1.0 x 10⁻¹⁴ at 25°C). The pKa and pKb are related by the equation pKa + pKb = 14, because the sum of pH and pOH in any aqueous solution is constant and equal to 14.
Given that the pKa of HA is 4.80 and pKb of BOH is 4.78, we can see that the salt BA will form a solution that is almost neutral but slightly basic, as the pKb is slightly lower than the pKa, implying a stronger base than acid. The pH of a solution of a weak base can be found by first determining the pOH (subtracting the pKb from 14) and then converting to pH by subtraction from 14. However, since Ka and Kb are so closely matched for the salt BA, the pH will be very close to 7. To be precise, it may be a fraction above 7, as the base is stronger by a small margin.
Therefore, the pH of the aqueous solution of the salt BA will be just above 7, and the closest answer choice is A) 7.01.