If the pK_a of HCHO₂ is 3.74 and the pH of an HCHO₂/NaCHO₂solution is 3.74,which of the following is true? A)[HCHO₂] [NaCHO₂] B)[HCHO₂] = [NaCHO₂] C)[HCHO₂]

Question

If the pK_a of HCHO₂ is 3.74 and the pH of an HCHO₂/NaCHO₂solution is 3.74,which of the following is true? A)[HCHO₂] > [NaCHO₂] B)[HCHO₂] = [NaCHO₂] C)[HCHO₂] < [NaCHO₂] D)[HCHO₂] << [NaCHO₂] E)It is not possible to make a buffer of this pH from HCHO₂ and NaCHO₂.

Quizplus · Accepted Answer

The pK_a of HCHO₂ is equal to the pH of the solution, which means that HCHO₂ is exactly half dissociated into H+ and CHO₂-. When an equal amount of NaCHO₂ is added to the solution, the Na+ ions will not have a significant effect on the pH, so the concentration of CHO₂- will remain the same as that of H+. Therefore, [HCHO₂] = [CHO₂-] = [NaCHO₂], so choice B is correct.

If the PKa of HCHO2 Is 3

If the PK_a of HCHO₂ Is 3