Which of the following solutions is not a buffer?
a. 125mL of 0.200M HCl added to 200mL of 0.400M CH3CO2-
b. 200mL of 0.400M HCl added to 125mL of 0.200M CH3CO2-
c. 200mL of 0.500M NaOH added to 200mL of 1.000M HF
d. 100mL of 0.500M H2PO4- added to 100mL of 0.100M HPO42-
e. 100mL of 0.200M HF added to 300mL of 0.200M NaF
The solution is given with a brief explanation of the correct multiple choice answer.