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CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 5   FOR BOARD EXAMINATION

QUESTION NO. 1

What is difference between soap and detergent? State in brief the cleansing action of soap in a movie and always got from a fabric. Why are so are not very effective when fabric is washed in hard water? How is this problem resolved.

ANSWER NO.1

          Soaps are sodium salt of long chain carboxylic acid. Whereas  detergents are sodium salt of long chain benzene sulphonic acid. Detergents are soluble in hard water, whereas so do not work in hard water. Dirts are oily in nature, all does not dissolve in water. The molecules of soap are Sodium and potassium salt of long chain carboxylic acid. The ionic end of soap interact with water while the  carbon chain interact with oil. The soap molecules, thus form structures called micelles where one end of the molecules towards the oil droplet while the ionic end faces  outside. This form and emulsion in water. The soap micelles thus  help in pulling out the dirt in water and clothes are cleaned.
            This is caused by the action of soap with calcium and magnesium salt, which cause the hardness of water. Hence a large amount of water is needed. 
              This problem is overcome by using another class of compound called detergent as a cleaning agent.

QUESTION NO. 2

(a) activity to demonstrate the decomposition reaction of Lead Nitrate.
(b) draw a labelled diagram of experimental setup. List to main observations.
(c) balanced chemical equation for the reaction stating the physical state of reactant and the product.

ANSWER NO. 2 


(a) 1. Take to take about 2 gram Lead Nitrate powder in a boiling tube.
2. Hold the boiling tube and heat over frame.

(b) OBSERVATION 


  • When Lead Nitrate is heated it produces a yellow precipitate of lead monoxide.
  • It also produces a brownish colour tube which is Nitrogen dioxide along with oxygen. 

 (c) 2Pb(NO3)2  ----------------->2PbO + 4NO2 + O2

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