When a 0.2 M solution of sodium hydroxide is added from a burette to 100 mL of a 0.100 M solution of the weak acid HA (Ka = 6.46x 10 -5 ).  

Answer the following and write the final answer only:  1. The volume of NaOH solution needed to reach the equivalence point is ……………………. 

2. Without any calculation the value of pH atequivalence point is …………………………..

3.  At the initial point, before any titrant has been added, the pH value is…………………….

4. At half equivalence point, pH value = ……………………. 5. for abuffer solution of HA with a pH = 7.3 and pKa = 4.3 , The ratio of [HA] / [A_] is .................