Class 10 NCERT Solutions Our Environment - NCERT Solutions prepared for CBSE students by the best teachers in Delhi.
Question 1: What would be the electron dot structure of carbon dioxide which has the formula CO2?
Answer: Electron dot structure of CO2 is
Question 2: What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (Hint − the eight atoms of sulphur are joined together in the form of a ring.)
Answer: Electron dot structure of a sulphur molecule
Question 3: How many structural isomers can you draw for pentane?
Answer: Three structural isomers are possible for pentane.
Question 4: What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Answer: The two features of carbon that give rise to a large number of compounds are as follows:
(i) Catenation - It is the ability to form bonds with other atoms of carbon.
(ii) Tetravalency - With the valency of four, carbon is capable of bonding with four other atoms.
Question 5: What will be the formula and electron dot structure of cyclopentane?
Answer: The formula for cyclopentane is C5H10. Its electron dot structure is given below.
Question 6: Draw the structures for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal
*Are structural isomers possible for bromopentane?
Question 7: Why do ionic compounds have high melting points?
Answer: Ionic compounds have strong electrostatic forces of attraction between the ions. Therefore, it requires a lot of energy to overcome these forces. That is why ionic compounds have high melting points.
Question 8: Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer: Since the conversion of ethanol to ethanoic acid involves the addition of oxygen to ethanol, it is an oxidation reaction.
Question 9: A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Answer: When ethyne is burnt in air, it gives a sooty flame. This is due to incomplete combustion caused by limited supply of air. However, if ethyne is burnt with oxygen, it gives a clean flame with temperature 3000°C because of complete combustion. This oxy-acetylene flame is used for welding. It is not possible to attain such a high temperature without mixing oxygen. This is the reason why a mixture of ethyne and air is not used.
Question 10: How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer: We can distinguish between an alcohol and a carboxylic acid on the basis of their reaction with carbonates and hydrogen carbonates. Acid reacts with carbonate and hydrogen carbonate to evolve CO2 gas that turns lime water milky. Alcohols, on the other hand, do not react with carbonates and hydrogen carbonates.
Question 11: What are oxidising agents?
Answer:Some substances such as alkaline potassium permanganate and acidified potassium dichromate are capable of adding oxygen to others. These are known as oxidising agents.
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