Q26 of 56 Page 1

While preparing soap a small quantity of common salt is generally added to the reaction mixture of vegetable oil and sodium hydroxide. Which one of the following may be the purpose of adding common salt?

Saponification is the reaction of alkaline hydrolysis of ethyl ethanoate. The Ethyl ethanoate is heated by addition of Sodium hydroxide results in formation of Sodium Ethanoate and Ethanol. Thus reaction is used for making soaps.



common salt is added to precipitate out the soap during saponification reaction because salt helps in decreasing the solubility of the soap and precipitating it out.

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24

Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles in old age. What type of lenses are required by the persons suffering from this defect to see the objects clearly?

Akshay, sitting in the last row in his class, could not see clearly the words written on the blackboard. When the teacher noticed it, he announced if any student sitting in the front row could volunteer to exchange his. Seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send the message to Akshay's parents advising them to get his eyesight checked.


In the context of the above event, answer the following questions:


(a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect?


(b) State the values displayed by the teacher and Salman.


(c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman?

 25

What do we observe on pouring acetic acid on red and blue litmus papers?

 27

A student takes about 4 mL of distilled water in four test tubes marked P, Q R and S.

He then dissolves in each test tube an equal amount of one salt in one test tube, namely sodium sulphate in P, potassium sulphate in Q calcium sulphate in R and magnesium sulphate in S. After that he adds an equal amount of soap solution in each test tube. On shaking each of these test tubes well, he observes a good amount of lather (foam) in the test tubes marked

 28

A student was asked to observe and identify the various parts of an embryo of a red kidney bean seed. He identified the parts and listed them as under:

I. Tegmen II. Testa


III. Cotyledon IV. Radicle V. Plumule


The correctly identified parts among these are: