You perform a potentiometric titration on the same water sample (100 mL) with 0.0155M HCl. The initial pH of the sample is 7.98. When you have added 3.56 cm3 the pH meter reads 6.98 you add a further 18.21 cm3 to reach a pH of 4.5. a) What is the buffer capacity of the sample? b) What is the alkalinity of the sample?