Question

The pH of a 25.0 mL sample of a buffer changed by one unit when 3.02 mL of 0.39 M HCl was added to it. What is the acid buffer capacity of this buffer? Express your answer in moles acid per L of buffer, according to the buffer capacity definition in your lab manual.

Answer 1

Buffer capacity is defined as number of moles of strong acid as base required to change the pH value of a 1 L buffer solution by 1 unit beta = Delta B/Delta pH Buffer capacity there, Delta B is number of moles of strong acid as base required to charge pH of 1 L of buffer solution and Delta pH is change in pH due to addition of strong acid or base. Volume of buffer solution = 25.0 mL volume of HCl added = 3.02 mL = 3.02 times 10^- 3 \r\n molarity of HCl is 0.39 M Delta pH = 1 given Calculate moles of HCl as follow M = n/V_in L molarity Thus, n = M times V = 0.39 times 3.02 times 10^- 3 L Therefore M = mol/L = 1.178 times 10^- 3 mol/L times L = 1.178 times 10^- 3 mol Now, beta = Delta B/Delta pH = n/V(1L) for 25 times 10^- 3, number of moles - 1.178 times 10^- 3 thus by