Calculate the pH when 59.0 mL of 0.229 M hydrochloric acid is mixed with 59.0 mL of 0.229 M sodium hydroxide solution at 25 °C. Calculate the pH when 59.0 mL of 0.229 M of a certain monoprotic weak acid, HA, is mixed with 59.0 mL of 0.229 M sodium hydroxide solution at 25 °C. For HA, the Ka is 6.9× 10-5.