5.16 Titration Practical

Question 1

What is a titration?

Answer 1

A titration is an experimental technique used to find out how much acid is needed to neutralise a quality of alkali or vice versa. You can then use this result to work out the concentration of the acid or alkali

Question 2

What is the equipment list for the titration experiment? (6)

Answer 2

• Burette
• Pipette
• White tile
• Clamp stand
• Conical flask
• Pipette filler

Question 3

What is the method to the titration experiment? (6)

Answer 3

• Say you want to find out the concentration of some alkali. Using a pipette and pipette filer, add a set volume of the alkali to a conical flask. Add two or three drops of indicator too.
• Use a funnel to fill a burette with a standard solution of an acid. Make sure you do this below eye level - you don’t want to be looking up if some acid spills over. Record the initial volume of the acid in the burette.
• Using the burette, add the acid to the alkali a bit at a time - giving the conical flask a regular swirl. Go especially slow when you think the end-point (colour change) is about to be reached
• The indicator changes colour when all the alkali has been neutralised
• Record the final volume of acid in the burette, and use it, along with the initial reading, to calculate the volume of acid used to neutralised the alkali
• Repeat the titration until you get ‘concordant results’, which means volumes of acid that are within 0.10cm cubed of each other
• Use the concordant results to calculate the mean volume of acid required to neutralise the alkali

Question 4

Why are indicators used in titration practicals?

Answer 4

When doing a titration, you must place an indicator in the conical flats so that you can tell when the acid has neutralised the alkali. Indicators show this by changing colour as the pH changes from alkaline to acidic

Question 5

What colour is litmus in acidic solutions?

Answer 5

Red

Question 6

What colour is litmus in alkaline solutions?

Answer 6

Blue

Question 7

What colour is Phenolphthalein in acidic solutions?

Answer 7

Colourless

Question 8

What colour is Phenolphthalein in alkaline solutions?

Answer 8

Pink

Question 9

What colour is methyl orange in acidic solutions?

Answer 9

Red

Question 10

What colour is methyl orange in alkaline solutions?

Answer 10

Yellow

Question 11

Which precaution reduces the risk of harm from acid burns?

Answer 11

Wearing gloves

Question 12

Why should you still the conical flask during the titration?

Answer 12

To evenly distribute the added acid/alkali

Question 13

Which piece of apparatus should you use to accurately measure the volume of your acid or alkali before transferring it to a conical flask?

Answer 13

Pipette

Question 14

How should you increase the accuracy of your titration?

Answer 14

To increase the accuracy of your titration and to spot any outliers, you need several consistent readings. The first titration you do should be a rough titration to get an approximate idea of the end-point. Then repeat the whole thing a few times, making sure you get (pretty much) the same answer each time (within 0.10cm cubed). Finally, calculate a mean of your results, ignoring the rough titration and any outliers