Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

The p-Block Elements

Short Answer Type

111.

Explain what happens when boric acid is heated.

348 Views

112.

Explain what happens when boric acid is added to water?

297 Views

113.

Why is boric acid considered as a weak acid ?

748 Views

114.

Explain the structure of boric acid.

143 Views

115.

Name the elements of group 14 and write down their electronic configuration.

214 Views

Long Answer Type

116.
How do elements of group 14 occur in nature? Give their uses.

Occurrence of Group 14 elements:

Occurrence of Carbon and its uses. Carbon is one of the most important element since it is an essential constituent of most of the compounds found in plants and animals. It occurs:
(i) In native state. Carbon occurs in native state as diamond, graphite and coal.
(ii) In combined state.
(a) It occurs in all living organisms, plants and animal body as proteins, carbohydrates, fats and other complex compounds.
(b) Atmosphere. It is present as CO₂ to the extent of 0.03 percent.
(c) Hydrocarbon. It occurs as hydrocarbons in marsh gas, petroleum, paraffin, vaseline, paper, cloth etc.
(d) Minerals. It occurs widely in minerals such as chalk, marble, kanker, lime stone which are different varieties of calcium carbonate ; magnesite, MgCO₃ ; dolomite, MgCO₃. CaCO₃ ; spathic ore of iron, FeCO₃ ; zinc carbonate ZnCO₃, etc.

Uses of diamond. It is used
(i) for making dies for drawing thin wires from metals and
(ii) in cutting glass and drilling rocks. Uses of graphite. It is used (i) in the manufacture of lead pencils and (ii) in making graphite electrodes. Occurrence of Silicon and its uses Occurrence. Silicon is the second most abundant (27.2 % ) element in the earth’s crust. It comes next to oxygen (45.5 % ) only. However, it does not occur in the free state. In the combined state, silicon is an important constituent of igneous rocks which consist of silicates of magnesium, aluminium, potassium or iron. Silicon is widely present as silica (SiO₂) in various forms such as sand, quartz, flint etc.

Uses: (i) Silicon is used in the manufacture of certain alloys as ferrosilicon, silicon bronze, manganese silicon bronze etc.
(ii) Very high purity silicon is used as semi conductor in transistors.
(iii) Silicon when added to steel, increases its resistance to the attack by acids.

Occurrence of Tin and its uses:
Occurrence. Tin occurs in free state at some places but occurs widely in a number of minerals e.g. sulphide ores of copper, zinc and iron. The most common ore of tin is tin stone or cassiterite, SnO₂Uses. Tin is used:
(i) in tinning brass untensils,
(ii) in the manufacture of alloys (Bronze, Gun metal, Solders etc.),
(iii) in the form of tin foil for wrapping cigarettes,
(iv) as tin amalgam in making mirrors.

Occurrence of Lead and its uses:
Occurrence. Lead is found in native state in small traces. It is found largely in the combined state.
The important minerals of lead are:
(i) Galena: lead sulphide (PbS)
(ii)Cerussite: lead carbonate (PbCO₃)
(iii) Anglesite: lead sulphate (PbSO₄)
(iv) Crocoisite: lead chromate (PbCrO₄).
Uses. It is used:
(i) in making cable coverings,
(ii) in making bullets, shots and lead accumulators,
(iii) in marking lead chambers for sulphuric acid plant,
(iv) in making tetraethyl lead, Pb(C₂H₅)₄, which is used as an anti knocking agent in petrol,
(v) in making various lead alloys such as solder, type metal and pewter.

150 Views

Short Answer Type

117.

Why does carbon act as abrasive and also as lubricant?

236 Views

Long Answer Type

118.

Discuss the characteristics of group 14 elements in terms of:
(i) Atomic radius
(ii) Ionisation enthalpy
(iii) Electropositive character
(iv) Melting and boiling points.

201 Views