CARBON AND ITS COMPOUNDS

Carbon and Its Compounds Class 10 Exemplar Problems

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Multiple choice questions:

Q-1: Carbon exist in the atmosphere in the form of

(a) Only carbon monoxide

(b) Carbon monoxide in traces and carbon dioxide

(c) Only carbon dioxide

(d) Coal

Solution: (c)

Carbon exists in the atmosphere in the form of carbon dioxide gas CO₂ in air (only 0.03%). Carbon also occurs in the earth’s crust in the form minerals likes carbonates. It also occurs in the form of fossil, organic compounds, wood, cotton and wool, etc.

Q-2: Which of the following statements are usually correct for carbon compounds? These

(i) are good conductors of electricity

(ii) are poor conductors of electricity

(iii) have strong forces of attraction between their molecules.

(iv) do not have strong force of attraction between their molecules.

(a) (i) and (iii)                         (b) (ii) and (iii)                         (c) (i) and (iv)                          (d) (ii) and (iv)

Atomic number of carbon is 6. So, its electron configuration is 2, 4. It can achieve the inert gas electron arrangement only by the sharing of electrons.

Solution: (d)

Carbon mainly forms covalent compounds, which due to the absence of free ions are generally poor conductors of electricity. Also the forces of attraction in between their molecules are week.

Q-3: A molecule of ammonia NH₃ has

(a) Only single bound                                                                (b) Only double bonds

(c) Only triple bonds                                                                  (d) two double bonds and one single bond   

Atomic number of N is 7.

Its electronic configuration is 2, 5 so it needs 3 more electrons to complete its octet. It gains 3 electrons each form 3 hydrogen atoms. Also N has one lone pair of electrons.

Solution: (a)

A molecule of ammonia has only single bonds and these are covalent bonds.

Note: The pair of electrons on the nitrogen atom in  molecule which is not involved in bond formation is called lone pair.

Q-4: Buckminsterfullerene is an allotropic form of

(a) phosphorus                                (b) sulphur                               (c) carbon                              (d) tin

Solution: (c)

Buckminsterfullerene is an allotrope of carbon containing clusters of 60 carbon atoms joined together to form spherical molecules. Its formula is C₆₀ (C-Sixty). It is a dark solid at room temperature and compared to another allotropic form of carbon (diamond and graphite), it is neither very hard nor soft.

Q-5: Which of the following are correct structural isomers of butane?

Isomers are compounds having the same molecular formula but different structures. Molecular formula of butane is C₄H₁₀

Solution: (a)

Structure (i) is n-butane

Structure (iii) is iso-butane

Since the molecular formula is the same, only structures are different. So (i) and (ii) isomers while structure (ii) and (iv) have molecular formula C₄H₈

In the above given reaction, alkaline KMnO₄ acts as

(a) reducing agent                                                                            (b) oxidizing agent

(b) catalyst                                                                                        (d) dehydrating agent

Oxidizing agent is a substance which given oxygen to the compound for oxidation (i.e., oxygen is removed from it) or which hydrogen from the compound. In other word we can say that CH₃CH₂OH is oxidised to CH₃COOH in the presence of oxidising agent like alk KMnO₄

Solution: (b)

KMnO₄ acts as oxidizing agent because it removes hydrogen from  and adds one oxygen to it.

Q-7: Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of

(a) addition reaction                                                                      (b) substitution reaction

(c) displacement reaction                                                             (d) oxidation reaction

Solution: (a)

Oils are unsaturated compounds containing double bonds. Addition reactions are characteristics property of the unsaturated hydrocarbons. The given reaction is an example of addition reaction.

Q-8: In which of the following compounds OH is the functional group?

(a) Butanone                               (b) Butanol                              (c) Butanoic                             (d) Butanal

Solution: (b)

(c) displacement reaction                                                                         (d) oxidation reaction

Solution: (a)

Oils are unsaturated compounds containing double bonds. Addition reactions are characteristics property of the unsaturated hydrocarbons. The given reaction is an example of an addition reaction.

Q-9: The sop molecular has a

(a) hydrophilic head and a hydrophobic tail

(b) hydrophobic head and a hydrophilic tail

(c) hydrophobic head and a hydrophobic tail

(d) hydrophilic head and a hydrophilic tail

Solution: (a)

A soap molecular is made up two part: A long hydrocarbon part and a short ionic part group. The long hydrocarbon chain is hydrophobic (water repelling) and ionic portion is hydrophilic (water attracting).