21.3 neutralisation

Question 1

define the equivalence point on a titration curve

Answer 1

centre of the vertical section on the pH titration curve

Question 2

define the equivalence point

Answer 2

volume of one solution that exactly reacts with the volume of the other solution

Question 3

what is an acid-base indicator?

Answer 3

a weak acid that has a distinctively different colour from its conjugate base

Question 4

define the end point

Answer 4

indicator contains equal concentrations of HA and A- and the colour will be between the two extreme colours

Question 5

what is the colour of the weak acid and conjugate base in methyl orange?

Answer 5

weak acid is red
conjugate base is yellow

Question 6

what colour is the methyl orange at first when a strong base is being added to a strong acid?

Answer 6

methyl orange is red because of high concentration of H+ ions which forces equilibrium to the left

Question 7

what happens when you add OH- ions to the methyl orange and acid solution?

Answer 7

OH- ions react with H+ in the indicator which forms water
weak acid dissociates shifting equilibrium position to the right
the colour changes first to orange at the end point and then to yellow as the equilibrium position is shifted to the right

Question 8

what happens when you add acid to a basic solution and methyl orange indicator?

Answer 8

H+ ions react with conjugate base
equilibrium position shifts to the left
the colour changes first to orange at the end point and finally to red when the equilibrium position has shifted to the left

Question 9

the pH of the end point is the same as…

Answer 9

the pKa value of HA

Question 10

what indicator must you use for a titration?

Answer 10

one that has a colour change which coincides with the vertical section of the pH titration curve

Question 11

what is there no indicator suitable for?

Answer 11

a weak acid- weak base titration