CBSE Class 10 Science Chemistry Cleaning Capacity of Soap Assignment

CBSE Class 10 Science Chemistry Cleaning Capacity of Soap Assignment. Students are advised to refer to the attached assignments and practice them regularly. This will help them to identify their weak areas and will help them to score better in examination. Parents should download and give the assignments to their children for practice.

Aim: To study the comparative cleaning capacity of a sample of soap in soft and hard water.

Materials required: beakers, test tubes,Distilled water, Calcium chloride,glass rods,Pre -prepared soap solution ,Measuring cylinder ,Measuring scale etc

Theory: Although soap is a good cleaning agent, its cleaning capacity is reduced when used in hard water. Hardness of water is due to the presence of sulphates, chlorides or bicarbonate salts of Ca²⁺ or Mg²⁺ ions. Soaps are sodium or potassium salts of long chain fatty acids. When soap is added to hard water, the Ca2+ and Mg2+ ions present in hard water react with soap. The sodium salts present in soaps are converted to their corresponding calcium and magnesium salts which are precipitated as scum. The insoluble scum sticks on the clothes and so the cleaning capacity of soap is reduced.

Ca²⁺ + 2 RCOONa→ (RCOO)₂Ca + 2Na⁺

The cleaning action of soap is very effective in soft water because it contains negligible calcium and magnesium ions.

Procedure:

¶ Take three beakers and label them as A, B and C.

¶ In beaker A, put 20ml of distilled water using a measuring cylinder.

¶ In beaker B, put 20 ml of tap water using another measuring cylinder.

¶ In beaker C, add 20 ml of tap water. To this, add 2 g of calcium chloride and stir with a glass rod till it dissolves.

¶ Add 10 ml of soap solution to each beaker.

¶ Stir the contents in the beakers with separate glass rods to ensure that soap has mixed properly.

¶ In beaker A, the soap solution formed is almost clear, in beaker B, some turbidity is observed and in beaker C scum is formed.

¶ Take three pieces of white cloth of size 5 cm x 5 cm each.

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