Studying saponification reaction for preparation of soap
To study saponification reaction for preparation of soap.
- Two beakers (250 mL)
- Two test tube
- A glass rod
- A measuring cylinder (50 mL)
- Wire gauge
- 20% sodium hydroxide solution : 30 mL
- Distilled water
- Vegetable oil (cotton seed oil, soyabean oil, palm oil) : 20 mL
- sodium chloride (common salt) : 10 g
- Red and blue litmus paper strips.
Soaps are sodium or potassium salts of long chain fatty acids. The process in which soap is produced is called saponification. Oils and fats are triesters or triglycerides of fatty acids. When a fat or oil reacts with a base like sodium hydroxide or potassium hydroxide, salts of fatty acids or soaps are formed along with glycerol. Addition of NaCl causes the precipitation of soap.
- Take nearly 20 mL of vegetable oil (preferably palm oil) in a 250 mL beaker. Warm it gently to melt, if needed.
- Add 30 mL of 20% sodium hydroxide solution with constant stirring.
- Successively dip the red and blue litmus paper into this reaction mixture. Do you find any change in colour of any litmus paper strip. Note and record your observation.
- Touch the beaker from outside. Is it hot or cold? Note and record your observation.
- Heat the beaker containing the reaction mixture on a wire gauge with constant stirring till it thickness.
- Add 10 g of common salt to this. Stir the mixture well and allow it to cool.
- Leave the mixture for some time (nearly 24 hours) till the soap set to a semi-solid mass floating on the top a solution.
- Remove the soap cake and cut it into desired shape.
- The colour of red litmus turns blue, whereas the colour of blue litmus does not change.
- Beaker containing reaction mixture gets warm.
- Soap solution is basic in nature.
- Saponification reaction is an exothermic reaction as heat is released during the course of the reaction.
- Stir the reaction mixture carefully so that it does not spill out.
- Use a wire gauge to heat the reaction mixture.
- Let the soap set and float on the spent lye before removing it form the beaker.
- Sodium hydroxide is hydroscopic in nature. Therefore, store it in an air-tight container.
- Sodium hydroxide is highly corrosive in nature. Therefore, handle it carefully.
- To study the dependence of current on the potential difference with graph
- Determination of equivalent resistance of two resistors when connected in series
- Determination of equivalent resistance of two resistors when connected in parallel
- Determination of the focal length of Concave mirror by obtaining the image of a distant object
- Determination of the focal length of Convex lens by obtaining the image of a distant object
- Tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence
- Tracing the path of the rays of light through a glass prism
- Finding the pH of the samples by using pH paper/universal indicator
- Studying the properties of acids and bases (HCl & NaOH) on the basis of their reaction
- Performing and observing the reactions and classifying them into: i. Combination reaction, ii. Decomposition reaction, iii. Displacement reaction and iv. Double displacement reaction
- Observing the action of Zn, Fe, Cu and Al metals on the salt solutions
- Studying the properties of acetic acid (ethanoic acid)
- Studying saponification reaction for preparation of soap
- Studying the comparative cleaning capacity of a sample of soap in soft and hard water
- Preparing a temporary mount of a leaf peel to show stomata
- Showing experimentally that light is necessary for photosynthesis
- Experimentally show that carbon dioxide is given out during respiration
- Studying (a) binary fission in Amoeba, and (b) budding in yeast with the help of prepared slides
- Studying homology and analogy with the help of models/charts of animals and models/charts/specimens of plants
- Identification of the different parts of an embryo of a dicot seed (Pea, gram or red kidney bean)