Advertisements
Advertisements
प्रश्न
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Advertisements
उत्तर
Copper reacts with moist carbon dioxide in the air to form copper carbonate, which causes a copper vessel to lose its shiny brown surface and form a green layer of copper carbonate. The citric acid present in lemon or tamarind neutralises the base copper carbonate and dissolves the layer. That is why tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface its characteristic lustre.
\[\ce{2Cu + \underset{(Present in air)}{H2O + CO2 + O2} -> \underset{(green)}{\underset{Basic copper carbonate}{CuCO3.CU(OH)2}}}\]
APPEARS IN
संबंधित प्रश्न
A solution of CuSO4 in water is .................... in colour.
(a) Pink
(b) Blue
(c) Colourless
(d) Green
Iron is
(a) More reactive than zinc
(b) More reactive than aluminium
(c) Less reactive than copper
(d) Less reactive than aluminium
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
What name is given to those metal oxides which show basic as well as acidic behaviour?
How would you show that silver is chemically less reactive than copper?
Explain why, metals usually do not liberate hydrogen gas with dilute nitric acid.
What happens when a rod of zinc metal is dipped into a solution of copper sulphate? Give chemical equation of the reaction involved.
Can we keep sodium immersed under water? Why?
Name two metals (other than zinc and iron) which can displace hydrogen from dilute hydrochloric acid?
What is the action of water on aluminium ? Write equation of the chemical reaction involved.
You are given samples of three metals − sodium, magnesium and copper. Suggest any two activities to arrange them in order of their decreasing reactivities.
One of the following is not a neutral oxide. This is:
(a) CO
(b) H2O
(c) N2O
(d) Na2O
Out of the following oxides, the amphoteric oxide is:
(a) Fe2O3
(b) Al2O3
(c) P2O5
(d) N2O
Metal A burns in air, on heating, to form an oxide A2O3 whereas another metal B burns in air only on strong heating to form an oxide BO. The two oxides A2O3 and BO can react with hydrochloric acid as well as sodium hydroxide solution to form the corresponding salts and water.
(a) What is the nature of oxide A2O3?
(b) What is the nature of oxide BO?
(c) Name one metal like A.
(b) Name one metal like B.
CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)
FeSO4(aq) + Zn(s) → ZnSO4(aq) + Fe(s)
On the basis of the above reactions, indicate which is most reactive and which is least reactive metal out of zinc, copper and iron.
Which of the following reactions will not occur? Why not?
(a) MgSO4 (aq) + Cu (s) → CuSO4 (aq) + Mg (s)
(b) CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)
(c) MgSO4 (aq) + Fe (s) → FeSO4 (aq) + Mg (s)
If A, B, C, D, E, F, G, H, I, J and K represent metals in the decreasing order of their reactivity, which one of them is most likely to occur in a free state in nature?
Name a metal which It does not react with any physical state of water?
When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?
A zinc plate was kept in a glass container having CuSO4 solution. On examining it was found that the blue colour of the solution is getting lighter and lighter. After a few days, when the zinc plate was taken out of the solution, a number of small holes were noticed in it. State the reason and give chemical equation of the reaction involved.
