Chapter Chosen

Carbon and its Compounds

Book Chosen

Science

Subject Chosen

Science

Book Store

Download books and chapters from book store.
Currently only available for.
CBSE Gujarat Board Haryana Board

Previous Year Papers

Download the PDF Question Papers Free for off line practice and view the Solutions online.
Currently only available for.
Class 10 Class 12

Write the name and formula of the 2nd member of homologous series having general formula CnH2n.


Alkene series has the general formula of CnH2n. Propene is the second member of the alkene family and has C3Has the molecular formula.

4268 Views

(a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:

(i) Physical state

(ii) Taste

(iii) NaHCO3 test

(iv) Ester test

(b) Write a chemical reaction to show the dehydration of ethanol.


(a)

Property

Ethanol

Ethanoic acid

  (i)

Physical state

Ethanol is a colorless liquid with pleasant odor

Ethanoic acid is colorless, pungent smelling liquid

(ii)

Taste

Ethanol is bitter to taste

Ethanoic acid is sour to taste

(iii)

NaHCO3 test

Ethanol does not react with sodium bicarbonate

When ethanoic acid reacts with sodium NaHCO3 with the evolution of carbon dioxide gas.

(iv)

Ester test

Ethanol on reaction with ethanoic acid in the presence of acid forms ester.

Ethanoic acid on reaction with alcohols in the presence of conc. Sulphuric acid to form ester./

 

(b) Ethanol undergoes dehydration to form ethane. 

 2 CH subscript 3 CH subscript 2 OH space rightwards arrow from Conc. space straight H subscript 2 SO subscript 4 to increment of space 2 CH subscript 2 equals CH subscript 2 space plus straight H subscript 2 straight O

2213 Views

(a) What is soap? Why are soaps not suitable for washing clothes when the water is hard?

(b) Explain the action of soap in removing an oily spot from a piece of cloth. 


(a) Soap is sodium or potassium salt of higher fatty acids such as oleic acid (C17H33COOH), stearic acid (C17H35COOH), palimitic acid (C15H31COOH), etc.

A soap is a sodium or potassium salt of long chain fatty acids. Hard water contains salts of calcium and magnesium. On adding soap to water, calcium and magnesium ions present in water displace sodium or potassium ions from the soap molecules forming an insoluble substance called scum. Scum results in wastage of soap.

 (b) Cleansing action of soaps: 

The oily spot present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the oily spot and remove it from the cloth. Then, the molecules of soap arrange themselves in the form of micelle and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence, the oily spots are easily rinsed away by water.

903 Views

Explain why carbon forms compounds mainly by covalent bond. Explain in brief two main reasons for carbon forming a large number of compounds. Why does carbon form strong bonds with most other elements?


Carbon has 4 electrons in its outermost shell and requires 4 more electrons to attain a noble gas electronic configuration. It cannot form an  ion, as a huge amount of energy is required for the removal of 4 valence electrons. The  ion thus formed will have 6 protons and 2 electrons, which will make it highly unstable. Carbon cannot form an  ion, as its nucleus with 6 protons cannot hold 10 electrons due to interelectronic repulsion. So, carbon achieves a noble gas electronic configuration only by sharing its 4 valence electrons with other elements. Thus, it forms compounds mainly by covalent bonds.

 The two main reasons for carbon forming a large number of compounds are as follows:

(a) Catenation: It is the ability of carbon to form bonds with other carbon atoms; this results in compounds having long branched chains and rings.  

(b) Tetravalency: Carbon has 4 valence electrons, so it is capable of forming covalent bonds with 4 other atoms.

The small atomic size of carbon enables it’s nucleus to strongly hold on to the shared pair of electrons. Hence, carbon forms strong bonds with most other elements.

4055 Views

What is the difference between the chemical composition of soaps and detergents? State in brief the action of soaps in removing an oily spot from a shirt. Why soaps are not considered suitable for washing where water is hard?


Sodium or potassium salts of long chain carboxylic acid are soaps. Whereas, detergents are ammonium or sulphonate salts of long chain carboxylic acid.

Cleansing action of soap:

Dirt which is present on the clothes cannot be removed solely by water as they are inorganic in nature and insoluble in water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.

The diagram details us of the cleansing action of soaps.


Soaps are not considered suitable when water is hard. Hard water contains salts of calcium and magnesium. A soap is a sodium or potassium salt of long chain fatty acids. 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. The formation of scum results in wastage of an enormous quantity of soap. 

1556 Views

List in tabular form three physical and two chemical properties on the basis of which ethanol and ethanoic acid can be differentiated.


Difference in physical properties of ethanol and ethanoic acid

Ethanol

Ethanoic acid

It is liquid at room temperature.

It often freezes in winter.

Its melting point is 156 K.

Its melting point is 290 K.

Its boiling point is 351 K.

Its boiling point is 391 K.

 

Difference in chemical properties of ethanol and ethanoic acid

Ethanol

Ethanoic acid

On reaction with metallic sodium, ethanol releases hydrogen gas.

Ethanoic acid does not release hydrogen gas on reaction with metallic sodium.

Ethanol does not release carbon dioxide gas on reaction with sodium bicarbonate.

Carbon dioxide gas is released when ethanoic acid is reacted with sodium bicarbonate.

964 Views