4.4.4: Titrations and pH curves

Question 1

pH curves

Answer 1

how the results of titration experiments

Question 2

X and y axis on pH curves

Answer 2

x axis: volume of base added

y axis: pH

Question 3

What is the requirement for an indicator

Answer 3

must change colour exactly at the end point of the titration,
changes colour over a narrow pH range

Question 4

Where must an indicator change colour on a pH curve?

Answer 4

change colour over a narrow pH range that lies entirely on the vertical part of the pH curve

Question 5

Indicators often used in acid-base titrations

2

Answer 5

methyl orange and phenophthalein

Question 6

Methyl orange colour change and at which pH

Answer 6

red at low pH
yellow at high pH
approx. pH of colour change: 3.1 - 4.4

Question 7

Phenolphthalein colour change and at which pH

Answer 7

colourless at low pH
pink at high pH
approx. pH of colour change: 8.3 - 10

Question 8

How to find the end point of weak acid/weak base titrations

and why

Answer 8

use a pH meter

because there’s no sharp pH change so no indicator will work