7. In each of the following questions, assume that there is no volume change when HCl is added to water in part (a) or the phosphate buffer in part (c). (a) Calculate the pH when 0.031 moles of HCl are added to 1.000 liter of water. (b) What is the difference between the pH of pure water (pH7.00) and the pH of the solution after HCl was added? (c) Calculate the pH when 0.031 moles of HCl are added to 1.000 liters of a buffer containing 0.112 MKH2PO4 and 0.383MK2HPO4. (d) The pH before the HCl was added is equal to 7.742. What is the difference between the pH before adding the HCl and after adding the HCl