Explore topic-wise InterviewSolutions in .

Uses of Coal are:

• Coal is used as fuel in factories and homes. 
• Coal is used to obtain coke, coal gas and coal tar. 
• Coal is used in thermal power plants for generation of electricity.

Methane, carbon dioxide.

Correct option is: (b) Propyne

Molecular formula – CO₂, Molecular mass – 44, Melting point -56.6 °C Percentage occurrence in air – 0.03%.

Correct option is: (a) 55% to 60%

• Graphite is a black, soft, brittle and dull form of carbon. 
• It is neither malleable nor ductile. 
• These properties of graphite make it unsuitable for making of ornaments.
• Hence, graphite is not used for making ornaments.

Properties of fullerenes are:

• Molecules of fullerenes are found in the form of buckyballs and buckytubes. 
• There are 30 to 900 carbon atoms in one molecule of a fullerene. 
• Fullerenes are soluble in organic solvents such as carbon disulphide, chlorobenzene.

Correct option is: (a) -182.5 °C

Correct option is: (c) glass cutting

Correctly matched column:

Correctly matched column:

Correct option is: (b) 3500 °C

Correct option is: (a) 186 carats

Correct option is: (d) single bond

• The German chemist Wohier synthesized an organic compound urca from an inorganic compound ammonium cyanate, 
• Ever since then, many organic compounds have been made from inorganic compounds.
• Carbon was found to he the main element in all these compounds. 
• Hence, organic chemistry is also referred to as chem is try of carbon corn pounds.

Uses of methane are:

• Methane in the form of natural gas is used in industries such as fabric mills, paper mills, food processing industry, petrol purification.
• Being the smallest hydrocarbon, the proportion of CO₂ released in the combustion of methane is small and, therefore, it is used as a domestic fuel.
• Methane is used for production of organic compounds such as ethanol, methyl chloride, methylene chloride and acetylene.

Physical properties of methane are:

• Melting point of methane is (-182.5 °C). 
• Boiling point of methane is (-161.5 °C). 
• It is a colourless gas. 
• The density of liquid methane is less than that of water. 
• Methane is sparingly soluble in water. It is highly soluble in organic solvents like gasoline, ether and alcohol. 
• Methane is in gaseous state at room temperature.

(1) True 

(2) False. Hydrocarbons with double bonds are called as Unsaturated hydrocarbons. 

(3) False. Ethene is Unsaturated hydrocarbon. 

(4) False. Covalent compounds are bad conductor of electricity. 

(5) True

Match the columns:

Correct option is: (d) CH₄

1. Ethene. It is an unsaturated hydrocarbon with double bond between two carbon atoms while rest are saturated hydrocarbons with single bond between two carbon atoms.

2. CaCO₃. It is a salt which is an inorganic’ compound, while rest are hydrocarbon compounds, i.e. organic compounds.

3. C₂H₂ . It is an unsaturated hydrocarbon with triple bonds while rest are saturated hydrocarbons with single bonds between two carbon atoms.

4. Methane. It is a marsh gas while rest are allotropes of carbon.

5. Cotton. Cotton is a natural fibre while rest all are fossil fuels.

6. Proteins. Proteins are carbonaceous nutrients while rest all are natural fibres.

7. Coal. Coal is a fossil fuel while rest all are carbonaceous nutrients.

8. Charcoal. Charcoal is a non-crystalline form of carbon while rest all are types of coal.

9. Ornaments. Ornaments are made from diamonds while rest all are made from graphite.

• Methane is formed by the decomposition of plant and animal matter in swamps or marshy areas. 
• As methane gas bubbles out from marshy area, it is called as marsh gas.

(a) The colour of the lead in the pencil is black as it is made from graphite which is an all otrophic form of carbon.

(b) The lead breaks easily as it is made up of graphite which is brittle in nature.

(c) When we start the electric current in the circuit, the bulb in the circuit glows, indicating that the lead in the pencil is a good conductor of electricity.

(d) (i) Lead dust does not dissolve in water nor in kerosene. 

(ii) It remains insoluble in both the test tubes.

Solvents such as water, kerosene and cooking oil do not dissolve coal powder in them.

Correct option is: (b) 16

Properties of diamond are:

• Brilliant and pure diamond is the hardest natural substance. 
• The density of diamond is 3.5 g/cm . 
• The melting point of diamond is 3500 °C. 
• When a diamond is heated at 800 °C in the presence of oxygen, CO₂ is given away. In this process no other product besides CO₂ is formed.
• Diamond does not dissolve in any solvent.
• Acids/bases have no effect on diamond.
• Diamond is a bad conductor of electricity as it does not have free electrons.

Correct option is: (a) 4%

Practical uses of CO₂ are:

1. CO₂ is used to make aerated drinks. 
2. CO₂ obtained by chemical reaction or kept under pressure is used in fire extinguishers. Liquified CO₂ is used to remove caffeine from coffee.
3. Liquid CO₂ is used as solvent in modem ecofriendly dry cleaning.
4. Solid carbon dioxide is used in cold storage and to keep milk and milk products and frozen substances cool during transport. It is also used for getting special effects of a mist in dramas and movies.

• Limewater traditionally means a weak solution of the alkali calcium hydroxide Ca(OH)₂ . 
• When CO₂ is passed through limewater, it reacts with calcium hydroxide to form insoluble particulates (precipitate) of Calcium carbonate (CaCO₃). 
• Calcium carbonate is weak basic salt and this gives a milky white precipitate. 
• Hence, lime water turns milky when CO₂ gas is passed through it.

Correct option is: (a) 4

Correct option is: (c) C₂H₆

Correct option is: (b) 2, 4

Carbon in its combined state exists as various compounds such as:

• Carbon dioxide and in the form of carbonates such as calcium carbonate, marble, calamine (ZnCO₃). 
• Fossil fuel – coal, petroleum, natural gas.
• Carbonaceous nutrients – carbohydrates, proteins, fats.
• Natural fibres – cotton, wool, silk. 
• Hydrocarbons – compound of carbon and hydrogen.

Uses of graphite are:

• Graphite is used for making lubricants. 
• Graphite is used for making carbon electrodes. 
• Graphite is used in pencils for writing. 
• Graphite is used in paints and polish. 
• Graphite is used in arc lamps which gives a very bright light.

Properties of graphite are:

• Graphite found in nature is black, soft, brittle and slippery. 
• Inside each layer of graphite, free electrons move continuously within the entire layer. That is why graphite is a good conductor of electricity.
• Due to the layered structure graphite can be used for writing on paper. 
• The density of graphite is 1.9 to 2.3 g/cm³.
• Graphite does not dissolve in most solvents.

Correctly matched column:

1. Density is defined as mass per unit volume of a substance, expressed as kilograms per cubic meter. 

2. At standard temperature and pressure, the density of air is 1.29 kg/m³. While that of carbon dioxide (CO₂) is 1.79 kg/m³. Hence, density of CO₂ is more than that of air.

• When substances melt or boil, bonds between the molecules are broken due to heat supplied. 
• On covalent compounds, the intermolecular forces of attraction are weak.
• Hence, intermolecular forces in covalent compounds are broken easily due to which they have low melting and boiling points.

Correct option is: (b) low melting point

• A compound is a substance formed when two or more elements are chemically bonded with each other in definite proportion by weight. 
• When atoms or two or more different elements chemically react with each other in a definite proportion by weight, a compound is formed.
• The properties of a compound are altogether different from its constituent elements.
• Example: Pure water is a compound made up of two elements Hydrogen and Oxygen. Hydrogen (H) atoms and oxygen (O) atoms have chemically reacted with each other in definite proportion to form a compound water (H₂O). The proportion of hydrogen and oxygen in water by volume is 2 : 1 and by weight is 1 :8 respectively.
• The properties of water are altogether different from the properties of its constituent elements, hydrogen and oxygen.

Fabric mills, paper mills, food processing industry, petrol purification.

Ethanol, methyl chloride, methylene chloride, acetylene.

Correct option is: (c) Methane gas