2 (f) Acids, alkalis and titrations

Question 1

Different Indicators

Answer 1

• Litmus
• Phenolphthalein
• Methyl Orange
• Universal Indicator

Question 2

Litmus

Answer 2

Acidic: Red
Alkaline: Blue

Question 3

Phenolpthalein

Answer 3

Acidic: Colourless
Alkaline: Pink

Question 4

Methyl Orange

Answer 4

Acidic: Red
Alkaline: Yellow

Question 5

Universal Indicator

Answer 5

Rainbow
Goes from red to purple as pH increases

Question 6

pH scale

Answer 6

a measure of how acidic/alkaline a solution is

Question 7

pH scale values

Answer 7

• 0-3 = strongly acidic
• 4-6 = weakly acidic
• 7 = neutral
• 8-10 = weakly alkaline
• 11-14 = strongly alkaline

Question 8

What can alkalis do?

Answer 8

Neutralise acids

Question 9

How to carry out an acid/alkali titration

Answer 9

1. Measure acid using pipette and pipette filler
2. Transfer to conical flask
3. Fill burette with alkali. Record initial reading of burette
4. Add a few drops of phenolpthalein indicator to conical flask
5. Add sodium hydroxide until colour change
6. Take final reading on burette
7. Work out alkali added: Final reading - initial reading

Question 10

Ways to make the titration accurate

Answer 10

• Rinse burette with alkali to remove impurities
• Rinse pipette with acid to remove impurities
• Swirl conical flask to mix
• Repeat and create an average with concordant results = 0.2cm3