Calculate the pH of a solution that is 0.205M benzoic acid and 0.230M sodium benzoate, a salt whose anion is the conjugate base of benzoic acid. (The pKa of benzoic acid

pH = 4.25

Explanation:

A solution composed of a weak acid and its conjugate base is a buffer solution. To calculate the pH of a buffer solution we use the Henderson-Hasselbach equation:

pH = pKa + log ([conjugate base]/[weak acid]

In this case, we have the following data:

[conjugate base] = [sodium benzoate] = 0.230 M

[weak acid] = [benzoic acid] = 0.205 M

The pKa of benzoic acid is 4.2. So, we introduce the data in the equation:

pH = 4.2 + log (0.230 M/0.205 M) = 4.2 + 0.050 = 4.25

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.