Question 1:

Ethane, with the molecular formula C₂H₆ has

(a) 6 covalent bonds.

(b) 7 covalent bonds.

(c) 8 covalent bonds.

(d) 9 covalent bonds.

Answer:

Correct Option: - (b) 7 covalent bonds.

One covalent bond is between 2 carbons and rest is with 6 hydrogens.

Question 2:

Butanone is a four-carbon compound with the functional group

(a) carboxylic acid.

(b) aldehyde.

(c) ketone.

(d) alcohol.

Answer:

Correct Option: - (c) Ketone.

The functional group of butanone is ketone.

 

 

Question 3:

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

(a) the food is not cooked completely.

(b) the fuel is not burning completely.

(c) the fuel is wet.

(d) the fuel is burning completely.

Answer:

Correct Option: - (b) the fuel is not burning completely.

 

 

Question 4:

Explain the nature of the covalent bond using the bond formation in CH₃Cl.

Answer:

Carbon forms bond by sharing its four electrons with other atoms.

Such bonds which are formed by the sharing of an electron pair between two atoms are known as covalent bonds.

In covalent bonding, both the atoms share the valence electrons, i.e., the shared electrons belong to the valence shells of both the atoms.

Here, carbon requires 4 electrons to complete its octet, while each hydrogen atom requires one electron to complete its duplet.

Also, chlorine requires an electron to complete the octet.

Therefore, all of these share the electrons and as a result, carbon forms 3 bonds with hydrogen and one with chlorine.

  

CH₃Cl

 

 

Question 5:

Draw the electron dot structures for

(a) ethanoic acid.

(b) H₂S.

(c) propanone.

(d) F₂ .

Answer:

Electron dot structures of

1. Ethanoic Acid:

1. H₂S:-

1. Propanone

1. F₂

 

 

Question 6:

What is a homologous series? Explain with an example.

Answer:

A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group.

For example, methane, ethane, propane, butane, etc. are all part of the alkane homologous series. The general formula of this series is C_nH_2n+2.

Methane CH₄

Ethane CH₃CH₃

Propane CH₃CH₂CH₃

Butane CH₃CH₂CH₂CH₃

It can be noticed that there is a difference of −CH2 unit between each successive compound.

 

 

Question 7:

How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

 

 

Answer:

Difference between ethanol and ethanoic acid on the basis of their physical and chemical properties are as follows:-

1. Ethanol has a pleasant smell whereas ethanoic acid has the smell of vinegar.
2. Ethanoic acid reacts with metal carbonates and metal hydrogen carbonates to form salt, water, and carbon dioxide gas while ethanol does not react with them.
3. The melting point of ethanoic acid is 17°C. This is below room temperature and hence, it freezes during winters.
4. Ethanol has no action on litmus paper whereas ethanoic acid turns blue litmus paper into red.
5. Ethanol has no reaction with sodium Hydrogen carbonate but Ethanoic Acid gives brisk Effervescence with Sodium hydrogen carbonate.
6. Ethanol has a burning taste where as ethanoic acid has a sour taste.

Metal Carbonates /Metal Hydro carbonates + carboxylic acid à salt + water + carbon dioxide

For Example: - 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂

Metal Carbonates/ Metal Hydrogen carbonates + Alcohols à No reaction

For Example: - CH₃CH₂OH + Na₂CO₃ à No reaction

 

Question 8:

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Answer:

A soap molecule has 2 ends one is hydrophilic i.e. it dissolves in water, and the other one is hydrophobic i.e. it dissolves in the oil or dirt.

Micelle formation takes place when soap is added to water as the hydrophobic part attracts dirt and grease.

No micelle will be formed in other solvents such as ethanol because the alkyl chain of soap becomes soluble in alcohol.

 Micelles can be formed only around suspended molecules of oil in a mixture.

Ethanol is a very good solvent and it can even dissolve oil to form a clear solution.

 

Question 9:

Why are carbon and its compounds used as fuels for most applications?

Answer:

Most of the carbon compounds give a lot of heat and light when burnt in air.

Saturated hydrocarbons burn with a clean flame and no smoke is produced.

The carbon compounds, used as a fuel, have high calorific values.

Therefore, carbon and its compounds are used as fuels for most applications.

 

 

Question 10:

Explain the formation of scum when hard water is treated with soap.

Answer:

Soap does not work properly when the water is hard. A soap is a sodium or potassium salt of long chain fatty acids.

Hard water contains salts of calcium and magnesium.

When soap is added to hard water, calcium and magnesium ions present in water displace sodium or potassium ions

from the soap molecules forming an insoluble substance called scum. A lot of soap is wasted in the process.

 

 

Question 11:

What change will you observe if you test soap with litmus paper (red and blue)?

Answer:

Since soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue.

 

 

Question 12:

What is hydrogenation? What is its industrial application?

Answer:

When hydrogen is added to unsaturated hydrocarbons in the presence of catalysts such as palladium or nickel they give rise to saturated hydrocarbons.

Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction itself being affected.

Commonly used catalyst in the hydrogenation of vegetable oils is nickel.

Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains.

Oils containing unsaturated fatty acids should be chosen for cooking.

 

Question 13:

Which of the following hydrocarbons undergo addition reactions?

C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄

Answer:

Unsaturated hydrocarbons undergo addition reactions. Being unsaturated hydrocarbons,

C₃H₆ and C₂H₂ undergo addition reactions.

 

 

 

Question 14:

Give a test that can be used to differentiate chemically between butter and cooking oil.

Answer:

Butter contains saturated fats. Therefore, it cannot be hydrogenated. On the other hand, oil has unsaturated fats.

That is why it can be hydrogenated to saturated fats (solids).

Bromine water test can be used to differentiate chemically between butter and cooking oil.

Add bromine water to a little of cooking oil and butter taken in separate test tubes.

1. Decolourising of bromine water by cooking oil shows it is an (unsaturated compound).
2. Butter (saturated compound) does not decolourise bromine water

 

 

Question 15:

Explain the mechanism of the cleaning action of soaps.

Answer:

The mechanism of the cleaning of soap can be described as below:-

1. Soaps are molecules in which the two ends have differing properties, one is hydrophilic,
2. that is, it dissolves in water, while the other end is hydrophobic, that is, it dissolves in hydrocarbons.
3. When soap is at the surface of water, the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ protruding out of water.
4. When soap is added to water in which dirty clothes are soaked, the two parts of the soap molecule dissolve in two different mediums.
5. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth.
6. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster.
7. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.