Page 50 - Chemistry ICSE Class IX

38 ICSE Chemistry – 9
ƒ Zinc ore, calamine (ZnCO ), decomposes on heating to give zinc
3
oxide (ZnO). This is an important step in the extraction of zinc metal.
heat
ZnCO (s) o ZnO(s) + CO (g)
2
3
zinc carbonate (calamine) zinc oxide carbon dioxide
ƒ Lead nitrate [Pb(NO ) ] on heating decomposes to give lead oxide
3 2
A н C o A C н (litharge) and brown fumes of nitrogen dioxide (NO ).
ŝƐƉůĂĐĞŵĞŶƚ ƌĞĂĐƟŽŶ 2
heat
2Pb(NO ) (s) o 2PbO(s) + 4NO (g) + O (g)
3 2
2
2
lead(II) nitrate lead(II) oxide nitrogen dioxide oxygen
(litharge)
What is a displacement reaction
A reaction in which one part (an atom or a group of atoms) of a molecule
is replaced by another is called displacement reaction. Displacement
reactions are also called substitution reactions. For example, the following
reaction
A + BC o AC + B

Ferrous sulphate crystals in which A displaces B from BC, is a displacement (or substitution) reaction.

ACTIVITY 2 Materials required: ŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ͕ ƚĞƐƚ ƚƵďĞƐ͕ njŝŶĐ ŵĞƚĂů͕ njŝŶĐ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ͕ ĐŽƉƉĞƌ͕ ŵĂŐŶĞƐŝƵŵ ĂŶĚ ŝƌŽŶ
Aim: dŽ ƐŚŽǁ ƚŚĂƚ ŵŽƌĞ ƌĞĂĐƟǀĞ ŵĞƚĂů ĐĂŶ ĚŝƐƉůĂĐĞ ůĞƐƐ ƌĞĂĐƟǀĞ ŵĞƚĂů ĨƌŽŵ ŝƚƐ ƐĂůƚ ƐŽůƵƟŽŶ ďƵƚ ƚŚĞ ƌĞǀĞƌƐĞ ŝƐ ŶŽƚ
ƉŽƐƐŝďůĞ

ŵĞƚĂůƐ
Procedure: dĂŬĞ ĂďŽƵƚ ϱ ŵů ŽĨ ĚŝůƵƚĞ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ ŝŶ Ă ƚĞƐƚ ƚƵďĞ͘ EŽƚĞ ŝƚƐ ĐŽůŽƵƌ͘ /ƚ ŝƐ ďůƵĞ͘ WůĂĐĞ Ă ƚŚŝŶ ƉůĂƚĞ
ŽĨ njŝŶĐ ŵĞƚĂů ŝŶ ƚŚĞ ƐŽůƵƟŽŶ ĂŶĚ ƐƟƌ ƚŚĞ ƐŽůƵƟŽŶ ǁŝƚŚ ŝƚ ĨŽƌ Ă ĨĞǁ ŵŝŶƵƚĞƐ͘ tŚĂƚ ĚŽ LJŽƵ ƐĞĞ͍
dŚĞ ďůƵĞ ĐŽůŽƵƌ ŽĨ ƚŚĞ ƐŽůƵƟŽŶ ĨĂĚĞƐ ĂǁĂLJ ĂŶĚ ƌĞĚ ƉƌĞĐŝƉŝƚĂƚĞ ŽĨ ĐŽƉƉĞƌ ƐĞƩůĞƐ ĚŽǁŶ͘ dŚŝƐ ĞdžƉĞƌŝŵĞŶƚ ƐŚŽǁƐ ƚŚĂƚ
njŝŶĐ ĚŝƐƉůĂĐĞƐ ĐŽƉƉĞƌ ĨƌŽŵ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ͘
EŽǁ͕ ƚĂŬĞ njŝŶĐ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ ŝŶ Ă ƚĞƐƚ ƚƵďĞ ĂŶĚ ƉůĂĐĞ Ă ĐŽƉƉĞƌ ǁŝƌĞ ŝŶ ŝƚ͘ ^ŚĂŬĞ ŝƚ ĨŽƌ ƐŽŵĞ ƟŵĞ ĂŶĚ ƐĞĞ ŝĨ ƚŚĞƌĞ ŝƐ
ĂŶLJ ĐŚĂŶŐĞ ŝŶ ĐŽůŽƵƌ Žƌ ĂŶLJ ƉƌĞĐŝƉŝƚĂƚĞ ŝƐ ĨŽƌŵĞĚ͘ dŚĞƌĞ ŝƐ ŶŽ ĐŚĂŶŐĞ ŝŶ ƚŚĞ ĐŽůŽƵƌ ŽĨ ƚŚĞ ƐŽůƵƟŽŶ ĂŶĚ ŶŽ ƉƌĞĐŝƉŝƚĂƚĞ
ŝƐ ĨŽƌŵĞĚ͘ dŚŝƐ ĞdžƉĞƌŝŵĞŶƚ ƐŚŽǁƐ ƚŚĂƚ ĐŽƉƉĞƌ ĐĂŶŶŽƚ ĚŝƐƉůĂĐĞ njŝŶĐ ĨƌŽŵ njŝŶĐ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ͘
ZĞƉĞĂƚ ƐŝŵŝůĂƌ ĞdžƉĞƌŝŵĞŶƚƐ ǁŝƚŚ ĂůƵŵŝŶŝƵŵ͕ ŵĂŐŶĞƐŝƵŵ ĂŶĚ ŝƌŽŶ ǁŝƚŚ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ ; Ϳ͘
&ƌŽŵ ƚŚĞ ĞdžƉĞƌŝŵĞŶƚƐ͕ ǁĞ ĮŶĚ ƚŚĂƚ ŵĂŐŶĞƐŝƵŵ ;DŐͿ͕ njŝŶĐ ;ŶͿ ĂŶĚ ŝƌŽŶ ;&ĞͿ ĐĂŶ ĚŝƐƉůĂĐĞ ĐŽƉƉĞƌ ĨƌŽŵ ĐŽƉƉĞƌ
ƐƵůƉŚĂƚĞ ƐŽůƵƟŽŶ ďƵƚ ĐŽƉƉĞƌ ŝƐ ŶŽƚ ĂďůĞ ƚŽ ĚŝƐƉůĂĐĞ ƚŚĞƐĞ ŵĞƚĂůƐ ĨƌŽŵ ƚŚĞŝƌ ƐĂůƚ ƐŽůƵƟŽŶƐ͘ ůů ƚŚĞƐĞ ŵĞƚĂůƐ ĂƌĞ͕
ƚŚĞƌĞĨŽƌĞ͕ ŵŽƌĞ ƌĞĂĐƟǀĞ ƚŚĂŶ ĐŽƉƉĞƌ ; ƵͿ͘
Conclusion: &ƌŽŵ ƚŚĞ ƌĞƐƵůƚƐ ŽďƚĂŝŶĞĚ͕ ŝƚ ĐĂŶ ďĞ ĐŽŶĐůƵĚĞĚ ƚŚĂƚ Ă ŵŽƌĞ ƌĞĂĐƟǀĞ ŵĞƚĂů ĐĂŶ ĚŝƐƉůĂĐĞ ůĞƐƐ ƌĞĂĐƟǀĞ ŵĞƚĂůƐ
ĨƌŽŵ ƚŚĞŝƌ ƐĂůƚ ƐŽůƵƟŽŶƐ͕ ďƵƚ Ă ůĞƐƐ ƌĞĂĐƟǀĞ ŵĞƚĂů ĐĂŶŶŽƚ ĚŝƐƉůĂĐĞ ŵŽƌĞ ƌĞĂĐƟǀĞ ŵĞƚĂůƐ ĨƌŽŵ ƚŚĞŝƌ ƐĂůƚ ƐŽůƵƟŽŶƐ͘
ƒ Displacement of copper (Cu) from copper sulphate solution
(CuSO ) by active metals like iron, zinc, lead and magnesium, is a
4
typical displacement reaction.
This displacement reaction can be demonstrated by performing the
following simple experiment:
Take about 5 mL of copper sulphate solution in a test tube. Place an
iron nail in the solution. Observe the change.
After some time, you will see
(a) blue colour of the copper sulphate solution fades away
(b) reddish deposit on the nail.
The reddish deposit on the nail is the displaced copper.
This experiment shows that iron displaces copper from copper
sulphate solution.
CuSO (aq) + Fe(s) o Cu(s) + FeSO (aq)
4
4
copper sulphate (blue) iron copper metal ferrous sulphate
(light green)