1. For each of the solutions below, determine the pH at equilibrium if 0.15 mmol/L of HCl is added.
   1. (10 pts) Pure water
   2. (35 pts) A buffered water to which a combination of H₂CO₃ and NaCO₃ has been added, which has a total carbonate concentration (C_T) of 100 mmol/L and a pH of 7. Assume [CO₃²] is negligible at all times, no exchange of carbonate/CO₂ with the atmosphere occurs (C_T is constant), and the following reactions are relevant:

H₂CO₃ HCO₃ + H⁺ pK_A = 6.3

Water dissociation pK_w = 14

Hint: first determine the concentration of Na⁺ initially present at pH 7, before HCl is added. Also, C_T = [H₂CO₃]+[HCO₃]

****** Please use Ka, charge neutrality and Ct to find the initial concentration of Na+, then use Ka, charge neutrality, Ct and Kw to find the Ph after the Hcl is added.*****