To Determine 5e Percentage Of Hypochlorite In Bleach

Question 1

Describe how a 25cm3 sample of the original bleach was diluted to exactly 500cm3.

Answer 1

Rinse a pipette with deionised water and fill up to mark bottom of the meniscus. Pour the bleach into a clean dry volumetric flask. Add deionised water up to the mark until bottom of the meniscus. Add drop- wise at the end as a froth can form. Read at eye level. Stopper and invert the flask 20 times.

Question 2

What colour developed when the potassium iodide and the sulfuric acid reacted with the
diluted bleach in the conical flask?

Answer 2

Reddish-brown colour

Question 3

Give two reasons why excess potassium iodide was used.

Answer 3

To keep iodine in solution as soluble potassium triiodide.

To ensure all the hypochlorite in bleach has reacted.

Question 4

the indicator used and state the colour change observed at the end point.

Answer 4

Starch. Blue-black to colourless