Page 42 - Science Class 08

this acid to different degrees. In the laboratory, 2Mg + 2HCI Õ 2MgCl + H 2
2
2
hydrogen is prepared by the ac on of dilute Fe + 2HCI Õ FeCI + H
hydrochloric acid on zinc. Aluminium, when 2 2
The table given below gives the reac ons of
fresh acts vigorously with hydrochloric acid.
various metals with air, water and dilute acids.
2AI + 6HCI Õ 2AICI + 3H
3 2

Metal With air With water With acids

Aluminium oxides mild with water steady reac on
strong on hea ng

Copper doesn’t burn no reac on with no reac on
but oxidises water, steam

Gold doesn’t burn and no reac on no reac on
forms no oxide
oxidises, forms no reac on steady reac on
Iron
H with water
2
burns to displace H , steady reac on
Magnesium 2
form oxides strong on hea ng

Silver oxides no reac on no reac on
burns bright strong reac on
Sodium steady reac on
and oxide with cold water

burns to bright steady reac on
Zinc doesn’t react
an oxide

We observe reac ons between metals and acids displaces the copper out of it and takes its
in day-to-day life also. Sauces, pickles, curd and place to form iron sulphate green in colour. It
juices of citrus fruits, when put into utensils of happens because iron is more reac ve than
copper.
iron or aluminium, form poisonous salts that are
Some similar reac ons are given below:
highly injurious to health. That is why such
Iron + Copper Sulphate Õ Copper + Iron
things are put into glass or plas c vessels.
Sulphate
Replacement Reac on Fe + CuSO₄ Õ Cu + FeSO
4
(blue) (green)
Magnesium+Copper Sulphate Õ Copper +
Take some copper sulphate solu on and put Magnesium Sulphate
an iron nail in it for a minute or two. Then Mg + CuSO₄ Õ Cu + MgSO 4
take the nail out and observe it carefully. You (blue) (colourless)
will see a layer of copper deposited on it. At Zinc + Copper Sulphate Õ Copper + Zinc
the same me, you will see that the blue Sulphate
colour of the copper sulphate has turned to Zn + CuSO₄ Õ Cu + ZnSO₄
be green. Why?
(blue) (colourless)
The iron nail when put into copper sulphate

42 Science-8