Answer the questions.[Che-3M]

Question 13 Marks

Nikita took $\mathrm{Zn}, \mathrm{Al}, \mathrm{Cu}, \mathrm{Fe}, \mathrm{Mg}$ and Na metal and put each metal in cold water and then hot water. She reacted the metal with steam
(i) Name the metal which reacts with cold water.
(ii) Which of the above metals react with steam?
(iii) Name the metal which reacts with hot water.
(iv) Arrange these metals in order of increasing reactivity.

Answer

(i) Na
(ii) $\mathrm{Al}, \mathrm{Zn}, \mathrm{Fe}$
(iii) Mg
(iv) $\mathrm{Na}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Cu}$

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Question 23 Marks

State one characteristic each of the chemical reaction which takes place when:
i. Dilute hydrochloric acid is added to sodium carbonate.
ii. Lemon juice is added gradually to potassium permanganate solution.
iii. Dilute sulphuric acid is added to the barium chloride solution.
iv. Quick lime is treated with water.
v. Wax is burned in the form of a candle.

Answer

i. When dilute hydrochloric acid is added to sodium carbonate - Evolution of carbon dioxide gas takes place.
ii. Lemon juice is added gradually to potassium permanganate solution - Change its colour from purple to colourless.
iii. When dilute sulphuric acid is added to the barium chloride solution - Formation of white precipitate of barium sulphate.
iv. Quick lime is treated with water - change in temperature.
v. Wax is burned in the form of a candle - Change in state from solid to liquid and gas.

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Question 33 Marks

2g of silver chloride is taken in a china dish and the china dish is placed in sunlight for some time. What will be your observation in this case ? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.

Answer

In this reaction, we will observed that the white colour of Silver chloride changes to Greyish white due to the formation of Silver metal. The decomposition of silver chloride is caused by light. This reaction is used in black and white photography.
- $2 \mathrm{AgCI}(\mathrm{s})$ Sunlight $2 \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}_{2}(\mathrm{~g})$
- Decomposition reaction / Photolytic decomposition.

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Science Answer the questions.[Che-3M]

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