A Buffer Is Composed of 0

Multiple Choice

A buffer is composed of 0.400 mol H₂PO₄^- and 0.400 mol HPO₄^2- diluted with water to a volume of 1.00 L.The pH of the buffer is 7.210.How many moles of HCl must be added to decrease the pH to 6.210?

A) 0.200 mol
B) 0.327 mol
C) 0.360 mol
D) 0.400 mol
E) 3.60 mol