Carbon and Its Compounds Important Questions

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Important Questions

Ques. Which organic compound is added to make ethanol unfit for drinking purposes? What is the name of the mixture formed?

Ans. Highly poisonous methanol is added in a small amount to ethanol to make it unfit for drinking purposes. The mixture is called methylated spirit or denatured alcohol.

Ques. A compound with the molecular formula C₂H₆O is used as a fuel. Identify the compound.

Ans. The compound is ethanol with the formula C₂H₅OH.

Ques. What is expected in the structures of the compounds methanol and ethanol?

Ans. They have the same functional group (—OH) known as an alcoholic group.

Ques.  Give the names of the following functional groups:

1. (–OH)
2.  (-COOH) 

Ans.  (i) Alcohol Group (ii) Carboxylic acid group

Ques. Name the products formed when ethanol burns in the air?

Ans. CO₂ and H₂O are formed.

C₂H₅OH (I) + 3O₂(g) = 2CO₂(g) + 3H₂O(I) + Heat + Light

Ques. What two forms of energy are liberated on burning alcohol?

Ans. Heat energy and Light energy.

Ques. What is meant by a saturated hydrocarbon?

Ans. Those hydrocarbons in which valiancy of carbon is satisfied by single bonds only are called saturated hydrocarbons.

Ques. Draw the structure of the ethanol molecule?

Ans. 

Ques. Give reasons for the following observation:

1. The element carbon forms a vast number of compounds.
2. The air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
3. The use of synthetic detergents causes pollution of water.

Ans. 

1. Carbons forms many compounds since carbon is small in size and can form stable covalent bonds (catenation), and it shows tetravalency.
2. Air holes of the gas burner are made open (adjusted) so that air can pass through, which is needed for complete combustion so that heated vessels do not get blackened.
3. Some synthetic detergent is not non-biodegradable, therefore, cause pollution of water.

Ques. Name the functional group present in each of the following organic compounds:
(i) C₂H₅CI
(ii) C₂H₅OH

Ans. 

1. (-Cl) Halogen (Chloro)
2. (-OH) Alcohol

Ques.  Name the functional group pr

esent in each of the following compounds:
(i) HCOOH
(ii) C₂H₅CHO

Ans.
(i) —COOH (Carboxylic acid)
(ii) —CHO (Aldehyde)

Ques. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is C_nH_2n.
Ans.
C₃H₆, H₂C=CH—CH₃
Propene is the second member of the series whose general formula is C_nH_2n.

Ques. List in tabular form three physical and two chemical properties based on which ethanol and ethanoic acid can be differentiated: -

Ans.

 Physical Properties:

Chemical Properties:

Ques. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in water having calcium and magnesium ions.

Ans. Detergents chemically are sodium or potassium salts of sulphonic acid of benzene or alkene.
Merits:

1. They work well with hard water.
2. They are more effective than soaps.

Demerits:

1. They are expensive.
2. Some of them having branching are non-biodegradable, therefore create water pollution.

Detergents are suitable for hard water having Mg²⁺ and Ca²⁺ ions because they do not form insoluble salts with Mg²⁺ and Ca²⁺ ions.

Ques. What is meant by Double Bond or Double Covalent Bond? Give Examples.

Ans. The bond between two atoms formed by sharing of two pairs of electrons is called a double bond. Two horizontal lines between two atoms denote a double bond example, O≡O (O₂).

Examples:

1. The formation of an Oxygen atom has six electrons in its outermost shell, two short of forming a complete octet. Thus, each oxygen atom in O2 shares 2 electrons with another oxygen atom to attain a stable configuration.
2. Formation of ethylene molecule (C₂H₂): In ethylene, two carbon atoms share two pairs of electrons between them—the rest two electrons on each carbon atom share one electron, each with two hydrogen atoms. Thus, ethylene molecules have one double bond (C=C) and four single bonds (C-H).

Ques. What is the product based on the Versatile Carbon Compound?

Ans. Food, clothes, medicines, books, or any of the things you listed are all based on this versatile carbon. In addition, all living structures are carbon-based. The amount of carbon present in the earth’s crust and the atmosphere is entirely merged. The earth’s crust has only 0.02% carbon in minerals (like carbonates, hydrogen-carbonates, coal and petroleum), and the atmosphere has 0.03% carbon dioxide. Despite this small amount of carbon available in nature, the importance of carbon seems to be immense.

Ques. What is a triple bond or triple covalent bond? Explain the formation of the triple bond giving two examples.

Ans. The bond formed between two atoms through the sharing of three electron pairs is called a triple bond. Three horizontal lines between two atoms denote a triple bond example; nitrogen molecule is as N≡N.

Examples:

1. Formation of N₂ molecules: Nitrogen atoms have five electrons in their outermost shells. Therefore, in N2 molecules two nitrogen atom shares 3 electrons and acquiring the stable structure and forming an N₂ molecule with a triple bond.
2. Formation of acetylene molecule (C₂H₂): In an acetylene molecule, each carbon atom satisfies its valency by sharing one electron with a hydrogen atom and sharing the other three electrons with the other carbon atom.

Covalent Bond

The covalent compound is formed when two atoms achieve stability by sharing electron pair, each contributing one electron pair. In this way, the atom can be regarded as having acquired a noble gas configuration.

Ques. Why is petrol regarded as a better fuel than kerosene?

Ans. In petrol, the combustion of hydrocarbons present is complete, and they burn with a blue flame. However, in kerosene, the discharge is not full. It burns with smoky flame accompanied by the release of unburnt carbon atoms. Therefore, petrol is regarded as a better fuel than kerosene.

Ques. What is a homologous series? Which two of the following organic compounds belong to the same homologous series?
C₂H₆, C₂H₆O, C₂H₆O₂,

Ans. Homologous series represent different families of organic compounds into which these are divided. Two characteristics of homologous series are listed.
The compounds CH₄O and C₂H₆O belong to the same homologous series known as alkanols.

Ques. State two characteristic features of carbon that give rise to a large number of carbon compounds when put together.

Ans.

1. The size of the carbon atom is tiny (Atomic radius = 77 pm)
2. The strength C—C bond is relatively high (355 kj mol^-1)

Therefore, any number of carbon atoms can be linked by covalent bonds; his self-linking property is called catenation.

Ques. What are the two properties of carbon which lead to the vast number of carbon compounds we see around us?

Ans. Carbon forms a large number of compounds due to the following properties:

(a) Catenation → Carbon shows the property of catenation that is the ability to form bonds with other carbon atoms forming long chains, both branched and unbranched chains, and even rings.

(b) Tetravalency → Carbon has valency 4; it can bond with four other carbon atoms or atoms of other non-covalent elements, giving rise to compounds with specific properties depending on the factors present in the mixture.

(c) Isomerism → Carbon compounds show the property of isomerism, which compounds the same molecular formula but a different structural formula.

Ques. How would you distinguish experimentally between alcohol and carboxylic acid?

Ans. 

1. Acid test: Reaction with carbonates/hydrogen carbonates. Take samples of alcohol and carboxylic acid in 2 test tubes, and add sodium carbonate or sodium bicarbonate solution to each. The compound which will produce brisk effervescence of CO2 gas will be acid.
2. Alcohol test: Take a small amount of ethanol and ethanoic acid in test tube A and B. Add 5% alkaline potassium permanganate drop by drop to this solution and warm the test tube.

The color of potassium permanganate will disappear in a test tube containing alcohol.

Ques. People use a variety of methods to wash clothes. Usually, after adding the soap, the beat, the clothes on a stone, or a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?

Ans. Soap lowers the surface tension of water. The long-chain non-ionic hydrocarbon group in soap gets attached to the oil or grease droplets and loosens them from cloth fibers along with the dirt. However, this loosening is insufficient to remove the grease with dirt altogether. Hence the clothes are agitated to eradicate the grease droplets.

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