1) Consider the titration of a weak acid with a strong base at the equivalence point. Choose all true statements that apply.

 

a) The pH is equal to the pKa of the acid.

b) All of the weak acid originally present in the solution has been converted into its conjugate base.

c) The moles of weak acid and its conjugate base are equal in the solution.

d) The moles of weak acid originally in the solution is equal to the moles of strong base added.

 

2) In a titration of a weak acid with a strong base, how is the pH calculated at the equivalence point?

a) Using weak base equilibrium

b) Using the concentration of a strong acid

c) Using weak acid equilibrium

d) Henderson-Hasselbalch equation

E) Using the concentration of strong base.

1)

b) All of the weak acid originally present in the solution has been converted into its conjugate base.

2

a) Using weak base equilibrium

d) Henderson-Hasselbalch equation

1)

a) The pH is equal to the pKa of the acid........Only true at the half equivalence point

b) All of the weak acid originally present in the solution has been converted into its conjugate base.....True, at equivalence point all the acid will be consumed.

c) The moles of weak acid and its conjugate base are equal in the solution...................False. At the equivalence all weak acid is gone

d) The moles of weak acid originally in the solution is equal to the moles of strong base added......False. This is only true for monoprotic acids, this won´t be the case for polyprotic acids.

2) In a titration of a weak acid with a strong base, how is the pH calculated at the equivalence point?

a) Using weak base equilibrium..........True

b) Using the concentration of a strong acid..........False. There is no strong acid

c) Using weak acid equilibrium................False. All weak acid is gone

d) Henderson-Hasselbalch equation...............True. You can always use the equation for weak acid/base equilibriums. Just be careful, you have to use the weak base equilibrium and make the proper analysis

E) Using the concentration of strong base..........False. At the equivalenence point the strong base will be consumed