CBSE Class 10 Science Carbon and its compounds Assignment Set E

Very Short Answer Type Questions :

Question. What change will you observe if you test soap with litmus paper (red and blue)?
Answer: Soap is alkaline in nature, hence it will turn red litmus into blue, blue litmus will remain blue.

Question. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is CnH₂n+1OH
Answer: Ethanol, C₂H₅OH or CH₃CH₂OH

Question. Why are carbon and its compounds used as fuels for most applications?
Answer: Carbon and its compounds undergo combustion to produce heat, the amount of heat released can be handled and used so they are used as fuels for most applications.

Question. Explain the formation of scum when hard water is treated with soap.
Answer: Hard water contains salts of calcium and magnesium. When soap molecule comes in contact with these salts it forms a curdy white precipitate (compound insoluble in water) called scum.
Soap + Hard water ⎯→ scum

Question. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is CnH₂n.
Answer: C₃H6, H₂C=CH—CH₃
Propene is second member of series whose general formula is CnH₂n.

Question. Write the name and formula of the first member of the carbon compounds having functional group —CHO.
Answer: 

Question. Give two uses of methane gas.
Answer: (i) It is used as a fuel (ii) It is the major component of biogas and CNG.

Question. Why do soaps form scum when added to hard water?
Answer: Hard water contains carbonate and sulphate salts of magnesium or sodium ions which react with the soap molecule to form a compound which is insoluble in water. Hence soaps form scum with hard water.

Question. What happens when ethanol burns in air?
Answer: Ethanol burns to form carbon dioxide and water.

Question. What is isomerism?
Answer: A property in which a compound can exist in different structural formula but its molecular formula remains the same.

Question. What is hydrophilic?
Answer: The substance showing attraction towards water is called hydrophilic.

Question. Name the second member of alkyne series.
Answer: Propyne

Question. Give the names of the functional group
(i) —CHO (ii) —C==O
Answer: (i) —CHO → Aldehyde (ii) (Img 28)

Question. The structural formula of an ester is
Name the alcohol and the acid from which it would have been formed.
Answer: Alcohol is C₂H₅OH ethanol
Acid is H3C—H₂C—COOH propanoic acid.

Short Answer Type Questions :

Question. (a) Why are covalent compounds generally poor conductors of electricity?
(b) Name the following compound:
(c) Name the gas evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?
Answer: 

Question. Give reasons for the following observations:
(a) The element carbon forms a very large number of compounds.
(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
(c) Use of synthetic detergents causes pollution of water.
Answer: (a) Carbon forms large number of compounds since carbon is small in size and can form stable covalent bonds (catenation) and it shows tetravalency.
(b) Air holes of 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.
(c) Some synthetic detergents are non-biodegradable, therefore, cause pollution of water.

Question. Name the compound formed when ethanol is warmed with ethanoic acid in the presence of a few drops of cone.H₂S0₄
Answer: 

Question. What happens when a small piece of sodium is dropped into ethanol?
Answer: Hydrogen gas will be evolved. 

Question. Give the electron dot structure of CH₃Cl and C₂H₂.

Answer: 

Question. Draw the electron dot structure of N₂ and NH₃.
Answer: 

Question. State two characteristic features of carbon which when put together give rise to large number of carbon compounds.
Answer: (i) Catenation (ii) Tetravalency of carbon

Question. Write the structural formula of chloroethane.
Answer: 

Question. Give reason for the following observations:
(a) The element carbon forms a very large number of compounds.
(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
(c) Use of synthetic detergents causes pollution of water. 
Answer: (a) Carbon forms large number of compounds due to its property of catenation, i.e. self linking. They form isomeric compounds i.e. compounds with same molecular formula but different structural formula.
(b) The vessels blacken due to deposits of black carbon particles on it which is caused due to incomplete combustion of fuel. Air holes are adjusted so that air enters through the holes and helps in complete combustion of the fuel.
(c) Synthetic detergent is non-biodegradable, it remains in the water thereby causing water pollution.

Question. What is meant by a functional group in an organic compound? Name the functional group present in
(i) CH₃CH₂OH
(ii) CH₃COOH
(b) State one point of difference between soap and synthetic detergent.
Answer: (a) Functional group is an atom or group of atoms or reactive part of compound, which determines chemical properties of compounds.
(i) —OH (Alcohol)
(ii) —COOH (Carboxylic acid)
(b) Soaps do not work well with hard water, detergents work well with hard water.

Question. Give two uses of ethanol and one harmful effect of it.
Answer: Ethanol is a good solvent so it is used in making medicines such as tincture iodine, cough syrups and many tonics. Ethanol is also used in making alcoholic drinks.
Harmful effects: Intake of small amount of ethanol leads to drunkenness. Intake of even small amount of ethanol can be lethal. Long-term use or consumption can lead to severe health problems.

Question. (a) Name the compound CH3COOH and identify its functional group.
(b) Give a chemical test to identify this compound.
(c) Name the gas evolved when this compound acts on solid sodium carbonate. How would you identify this gas?
Answer: (a) Ethanoic acid, functional group is—COOH (Caboxylic/group)
(b) Take few drops of ethanoic acid in a test tube and add sodium hydrogen carbonate solution to it. Brisk effervescence of CO2 gas is formed.
(c) CO₂ gas is evolved. To identify the gas, pass it through freshly prepared limewater, it turns milky due to the formation of milky white precipitate of CaCO3.
Ca(OH)₂ + CO₂ ⎯⎯→ CaCO₃ + H₂O

Question. (a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
(b) (i) Name the products formed when ethanol burns in air.
(ii) What two forms of energy are liberated on burning alcohol?
(c) Why is the reaction between methane and chlorine considered a substitution reaction?
Answer: (a) On adding bromine water, the unsaturated hydrocarbon decolourises the bromine water but the saturated hydrocarbon will not decolourise bromine water.
(b) (i) Ethanol burns in air to produce carbon dioxide and water.
C₂H₅OH + 3O₂ ⎯⎯→ 3CO₂ + 3H₂O + heat
(ii) Two forms of energy obtained are heat energy and light energy.
(c) When methane reacts with chlorine, the hydrogen atom of methane is replaced by chlorine atom step by step and hence it is termed as substitution reaction.
CH₄ + Cl₂ ⎯⎯→ CH₃Cl + HCl

Question. (a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
(b) (i) Name the products formed when ethanol burns in air. ‘
(ii) What two forms of energy are liberated on burning alcohol?
(c) Why is the reaction between methane and chlorine considered a substitution reaction?
Answer: 

Question. An organic compound ‘X’ which is also called antifree mixture has the molecular formula C₂H₆O ‘X’ on oxidation gives a compound ‘Y’ which gives effervescence with a baking soda solution. What can X and Y be? Write their structural formula.
Answer: X is ethanol, (C₂H₅OH)
Y is ethanoic acid (CH₃COOH)

Question. Write the structures of isomers of hexane.
Answer: 

Long Answer Type Questions :

Question. With the help of balanced chemical equations explain what happens when ethanol is heated with (i) alkaline solution of potassium permanganate, (ii) excess concentrated sulphuric acid at 443 K. Mention any two uses of ethanol.
Answer: 

Question. (a) What is homologous series? Give one example.
(b) What will happens if ethanoic acid reacts with ethanol in the presence of an acid as a catalyst? Name the reaction. Write the chemical reaction for this reaction.
(c) Why are soaps ineffective in hard water?
Answer: (a) Homologous series is series of compounds having same functional group and same chemical properties. When members of the series are arranged in ascending order, two successive members differ by –CH2 group and mass 14 u.
Example : Alcohol
CH3OH
CH2 mass 14. a.m.u
C2H5OH
C3H7OH
(b) Ethanol reacts with ethanoic acid to produce a fruity smelling compound called ester, the conc. sulphuric acid is used as dehydrating agent which removes water.
Such reaction is called esterification.
Example:

(c) Hard water contains salts of Ca and Mg. Soap molecule reacts with these salts to produce white precipitate called scum, which is insoluble in water and the cleansing action of soap becomes ineffective.

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

Question. (a) In 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.
Answer: 

Question. What are the hydrocorbons write the name and general formula of (i) sturated hydrocarbons, (ii) unsaturated hydrocarbons, and draw the structure of one hydrocarbon of each type. How can an unsaturated hydrocarbon be made saturated?
Answer: