Page 170 - Chemistry

 Phenolphthalein
 2m lead (II) nitrate
 0.05 M sodium thiosulphate
 Distilled water
 20% volume hydrogen peroxide
 Source of heat ( Bunsen burner)

Notes:
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1. 20% 20 volume peroxide is prepared by diluting 20cm of 20v hydrogen peroxide
to make 100cm 3
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2. solution T is 1.0 hydrochloric acid and is made by dissolution 86cm of 35-37%
hydrochloric acid diluted to 1litre of solution
3. solution S is 0.5m sodium hydroxide
4. solid V is exactly 1.5g of sodium carbonate ( anhydrous)
5. solid J is potassium iodide
6. solid M is 1.2g magnesium powder
7. solution K is 0.02m copper (II) sulphate

1. You are provided with the following :
 1.0M Hydrochloric acid; solution T.
 0.5M sodium hydroxide; solution S
 Anhydrous sodium carbonate of unknown mass: solid V.
You are required to determine the mass of sodium. Carbonate that was used in the experiment.

Procedure
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Measure 60cm portion of 1m hydrochloric acid using a measuring cylinder and transfer
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it to 100cm beaker. Add all sodium carbonate (solid V) to the acid in the beaker and
stir gently. Leave the mixture for 3 minutes until there is no effervescence transfer
the mixture into a clean 100ml measuring cylinder and add distilled water to make
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100cm of the solution. Transfer all the solution into 250cm beaker and shake
well, label this solution W.
Fill the burette with solution S.
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Pipette 25.0cm of solution W and transfer to a conical flask. Add 2-3 drops of phenolphthalein
indicator and titrate with solution S. Records your results in table I below.
Repeat the titration to get two more concordant values.

Table I
Experiment I II III

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Final burette reading (cm )
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initial burette reading (cm )
Volume of solutions S used

Transfer the mixture into a clean 100ml- measuring cylinder and add distilled water to
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make 100cm of the solution.
(a) Determine the average volume of solution S used.
(b). Calculate the number of moles of sodium hydroxide (solution S) used.
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(c). Find the number of moles of hydrochloric acid in 25cm of solution W.
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(d). Determine the number of moles of hydrochloric acid in 100cm
3
(e). Calculate the number of moles of hydrochloric acid in the original 60cm of solution.
(f). Calculate the number of moles of hydrochloric acid that reacted with sodium
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