CBSE Guess > Papers > Question Papers > Class X > 2009 > Science > Science
Q. 6. Write an expression for the heat produced H in time t in a heater of resistance R which is carrying a current I.
Ans. Heat produced, H = I2 x R x t joules
Where
Q. 7. Describe an activity to demonstrate the change that takes place when white silver chloride is kept in sunlight. State the type of chemical reaction which takes place.
Activity :
(i) About 2 g of silver chloride is taken in a china dish. It is white in colour.
(ii) This china dish is placed in sunlight for some time.
(iii) It will be observed that white silver chloride turns grey due to formation of silver metal. This is a decomposition reaction.
Q. 8. Describe an activity to demonstrate what is observed when solutions of sodium sulphate and barium chloride are mixed together in a test tube. State the type of chemical reaction that takes place. 2
Ans. Activity when solutions of sodium sulphate and barium chloride are mixed:
(i) About 3 ml solution of sodium sulphate is taken in a test tube.
(ii) In another test tube, 3 ml of barium chloride solution is taken.
(iii) When solutions of sodium sulphate and barium chloride are mixed, a white precipitate of barium sulphate is formed at once.
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