Question

The ph of a phosphate buffer is 7.10 at 25C. What is the pH of the buffer at 37C? The delta H for the relevant dissociation step is 3.75 kJ/mol.

Answer 1

Concept: As the temperature increases, the rate of dissociation of acid increases, as a result, [H⁺] increases, which indicates that pH decreases as pH = -Log[H⁺]

The pH = 7.10, which is closer to the pKa2 value of phosphoric acid (7.20 at 25 C)

In the standard books (biological buffers book), it's mentioned that its pKa2 value at 37 C = 7.16

Therefore, the resulting pH will also decrease by 7.20 - 7.16 = 0.04

i.e. The pH of the buffer at 37 C = 7.10 - 0.04 = 7.06