To simulate the pH of blood,which is 7.4,a buffer solution made by dissolving sodium dihydrogen phosphate (K_a= 6.2 $\times$10^-⁸)and sodium hydrogen phosphate (K_a= 3.6 $\times$10^-¹³)together in an aqueous solution can be used.What mole ratio of Na₂HPO₄/NaH₂PO₄ is required to produce a solution with a pH of 7.4?

Question

Quizplus · Accepted Answer

To maintain a pH of 7.4, the buffer solution must have an equal concentration of the weak acid and its conjugate base. First, we need to determine which compound is the weak acid and which is the conjugate base. In this case, sodium dihydrogen phosphate (Na₂HPO₄) is the weak acid and sodium hydrogen phosphate (NaH₂PO₄) is the conjugate base. We can use the Henderson-Hasselbalch equation to find the mole ratio: pH = pKa + log([conjugate base]/[weak acid]) 7.4 = 6.8 + log([NaH₂PO₄]/[Na₂HPO₄]) 0.6 = log([NaH₂PO₄]/[Na₂HPO₄]) Antilog(0.6) = [NaH₂PO₄]/[Na₂HPO₄] 3.98 = [NaH₂PO₄]/[Na₂HPO₄] Therefore, the mole ratio of Na₂HPO₄/NaH₂PO₄ is approximately 1.6. The correct answer is (B) 1.6.

To Simulate the PH of Blood,which Is 7 ×\times× 10-8)and Sodium Hydrogen Phosphate (Ka = 3

To Simulate the PH of Blood,which Is 7 $\times$ 10^-⁸)and Sodium Hydrogen Phosphate (K_a= 3