Identifying Bleaching Powder

The aim of this experiment is to identify bleaching powder among the given samples of chemicals. Bleaching powder contains a mixture of calcium hypochlorite (Ca(OCl)₂) and calcium chloride (CaCl₂). Hence, it is represented as CaOCl₂ and is also known as calcium oxychloride. When treated with dilute acid, like dilute sulphuric acid, it liberates hypochlorous acid (HClO) that decomposes to give nascent oxygen. Nascent oxygen is a very strong oxidising agent. It can oxidise the molecules, imparting colour to material and hence bleach it. Bleaching is the process of whitening or lightening a coloured fabric.

• 2CaOCl₂ (s) + H₂SO₄ (aq) → CaSO₄ (aq) + CaCl₂ (aq) + 2HClO (aq)
• HClO → HCl + [O] 

Apparatus and Materials Required

Apparatus:

• Bleaching powder
• Sodium chloride
• Ammonium chloride 
• Potassium chloride
• Dilute sulphuric acid,
• Beakers
• Magnetic stirrers with Stir bars
• Watch glasses
• Petri dish
• Yellow flower petals
• Distilled water
• Lime water

Procedure

The following steps to follow for the procedure:

1. Prepare a 5% solution of each sample given to you by dissolving 5 g of each sample in four different beakers labelled A, B, C and D, containing 100 mL water each.
2. Dip a petal in each solution.
3. Record the colour of the petal when dipped in the sample solution.
4. Take the petals out and dip them in four different beakers labelled 1, 2, 3 and 4 containing 50 mL dilute sulphuric acid each.
5. Gently stir the petals in the acid.
6. Record the colour of the petals dipped in the sample solution. 

In this experiment, we learnt that sample D is bleaching powder as it exhibited bleaching action. Bleaching powder reacts with dilute sulphuric acid to generate hypochlorous acid, which decomposes to give nascent oxygen. Nascent oxygen, a very strong oxidising agent, is responsible for the bleaching action.

FAQs on Identifying Bleaching Powder