Question

EXERCISES
9. What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution?
Write word equations of the reactions involved.
10. Saloni took a piece of burning charcoal and collected the gas evolved in a
test tube.
(a)
(b)
How will she find the nature of the gas ?
Write down word equations of all the reactions taking place in this
process.
11. One day Reeta went to a jeweller's shop with her mother. Her mother gave
an old gold jewellery to the goldsmith to polish. Next day when they brought
the jewellery back, they found that there was a slight loss in its weight.
Can you suggest a reason for the loss in weight?​

Answer 1

Answer:

9. (a) when dilute Sulfuric acid poured on Copper plate then Copper sulphate is formed as a precipitate and Hydrogen gas will be liberated .

(b)When iron nail is placed in the solution of Cupper sulphate solution , as Iron is more reactive in comparison to Copper , It will displace Copper from it's solution and Iron sulphate will be formed along with this Cupper will formed.

10 . here the liberated gas is CO2

We can know it's presence by passing it through Ca(OH)2.

If it forms whit precipitate then the evolved is certainly Carbon dioxide .

It's equation will be

Ca(OH)2+CO2--------->CaCO3+H2O

here CaCO3 is the white precipitate formed in the reaction.

11. To polish a gold ornament, it is dipped in a liquid called aqua regia (a mixture of hydrochloric acid and nitric acid). On getting the environment of aqua regia, the outer layer of gold dissolves and the inner shiny layer appears. The dissolving of the layer causes a reduction in the weight of the jewellery.

Answer 2

Answer:

[a] When a dilute Sulphuric acid is poured on a copper plate no reaction takes place due to less reactivity of copper..... Copper gets deposited on the iron nail and green solution is ferrous Sulphate solution.

[b] When an iron nail is dipped in copper sulphate solution, a brown coating of copper is formed on the surface of iron and the colour of copper sulphate solution changes from blue to light green.

10]a] Saloni needs to add some water in the test tube in which gas is collected. She needs to cover the test tube and shake it well. Now she will test the both solution with blue and red litmus which show the gas is acidic in nature.

[b] Charcoal reacts with oxygen to form carbon dioxide gas.

    C +O2------>CO2

Carbon dioxide reacts with water to form carbonic acid which is acidic in nature and turs blue litmus red.

    CO2+H2O--------->H2CO3

HOPE MY ANSWER WILL HELP YOU