What volume of 0.1mol/L hydrochloric acid solution should be added to 50 mLof the following solutions respectively to prepare solution at pH =7.00? (1) 0.1mol/L NaOH solution. (2) 0.1 mol/L NH3 solution (3) 0.1 mol/L Na2HPO4 If these solutions prepared are buffer solutions, and which one have the best buffer capacity.