Standardisation of a HCl Solution using a Standard Solution of Na2CO3

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Equipment:

• 0.1 M Sodium Carbonate solution
• Hydrochloric acid solution
• Methyl orange indicator
• Burette
• Pipette and filler
• Retort stand and clamp
• Conical flask
• Funnel
• White tile
• Wash bottle

Experiment:

1. Rinse conical flask, pipette and burette with deionised water.
2. Rinse pipette with sodium carbonate solution
3. Rinse burette with HCl
4. Pipette 25cm³ sodium carbonate solution into conical flask and add three drops methyl orange indicator
5. Using a funnel, fill burette with HCl above zero mark and remove funnel.
6. Allow acid to folw into a beaker until bottom of meniscus is at 0 mark
7. Make sure bottom of the tap is filled.
8. Carry out a rough titration by adding HCl to conical flask in 1cm³ lots, with swirling, over white tile  until colour of solution changes from orange to pink. Note burette reading.
9. Carry out two more accurate titrations.
10. Calculate concentration using formula.

Possible Questions:

1. Why was a white tile used?

To easily see colour changes

2. Why were only 3 drops indicator used?

The indicator is itself an acid, and too much would cause inaccuracies

3. Why were apparatus rinsed with solution before titration?

To remove residual water which would result in inaccuracies