RBSE Solutions for Class 10 Science Chapter 4 Carbon and Its Compounds

Rajasthan Board RBSE Solutions for Class 10 Science Chapter 4 Carbon and Its Compounds Textbook Exercise Questions and Answers.

RBSE Class 10 Science Solutions Chapter 4 Carbon and Its Compounds

RBSE Class 10 Science Chapter 4 Carbon and Its Compounds InText Questions and Answers

Page 61.

Question 1.
What would be the electron dot structure of carbon dioxide which has the formula CO₂?
Answer:
The electron dot structure of CO₂ is written as:

So, the structural formula of CO, is O = C = O

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:
Atomic number of sulphur =16
Electronic configuration = K, L, M 2, 8, 6
Hence, sulphur atom has 6 electrons in the outermost (valence) shell. Thus, it requires two electrons to complete its octet. So every sulphur atom will share two electrons.

Page 68.

Question 1.
How many structural isomers can you draw for Pentane?
Answer:
The molecular formula of Pentane is C₅H₁₂. Three structural isomers can be drawn for this, which are as follows:
(i)

Pentane (normal Pentane)
(ii)

Isopentane (2-Methyl butane)
(iii)

Neo Pentane (2, 2-Dimethyl propane)

Question 2.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Answer:
Catenation and tetravalency of carbon are the two properties which lead to the hug number of carbon compounds:

(i) Catenation:
Carbon has the ability to form bonds with other atoms of carbon, this property is called catenation. Carbon atoms may be linked by single, double or triple bonds.

(ii) Tetravalency:
Carbon has four valency so it is capable of bonding with four other atoms of carbon or atoms of some
other monovalent element. Compounds of carbon are formed with oxygen, hydrogen, nitrogen, sulphur, chlorine and many other elements.

Question 3.
What will be the formula and electron dot structure of cyclopentane?
Answer:
The molecular formula of cyclo pentane is C₅H₁₀. The structural formula and electron dot structure of this is as follows:

Question 4.
Draw the structures for the following compounds:
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone
(iv) Hexanal Are structural isomers possible for bromopentane?
Answer:
(i) Ethanoic acid: CH₃COOH

(ii) Brompentane: C₅H_nBr

(iii) Butanone: CH₃CH₂COCH₃

(iv) Hexana: C₆H₁₂O

yes, the structural isomers of bromopentane are possible, which can be eight in numbers.

Question 5.
How would you name the following compounds:

Answer:
Name of the above compounds can be given as:
(i) CH₃ – CH₂ – Br is obtained from Ethane. The prefix of Br present in the compound is Bromo, so the name of this compound is Bromo Ethane

(ii)

This compound belongs to Aldehyde group and the suffix of CHO group is ‘al’ so the name of this compound is Methanal. This is also called formaldehyde.

(iii)

This compound have six carbon atoms. Compound is unsaturated and a triple bond is also present on first position of carbon chain and the suffix for triple bond is ‘yne’. So the name of the compound is Hexyne or Hex-1-yne.

Page 71.

Question 1.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer:
The conversion of ethanol to ethanoic acid is oxidation reaction because oxygen is increased in this reaction. Ethanol contains one oxygen atom and acetic acid contains two oxygen atoms and addition of oxygen is oxidation. This oxidation is performed by oxidants, KMnO₄ or K₂Cr₂O₇ and hydrogen is removed from ethanol.

Question 2.
A tnixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used.
Answer:
The percentage of carbon is more in ethyne and the percentage of oxygen in air is only 20%. Remaining are mainly nitrogen with other gases so this amount of oxygen is not sufficient for complete combustion of ethyne. High temperature is required for welding. But complete combustion occurs when the mixture of ethyne and oxygen is burned. Thus, to ensure complete combustion and to obtain a high temperature required for welding, a mixture of ethyne and oxygen is used instead of ethyne and air.

Page 74.

Question 1.
How would you distinguish experimentally between an ‘ alcohol and a carboxylic acid?
Answer:
Alcohol (example C₂H₅OH) and carboxylic acid (like CH₃COOH) can be distinguished in the laboratory by the following tests :
(1) Alcohol has smell like spirit while carboxylic acid have pungent smell.
(2) Alcohol does not effect the blue litmus but carboxylic acid turns blue litmus into red.
(3) Alcohol does not react with NaHCO₃ while carboxylic acid reacts with NaHCO₃ and gives effervescence due to liberation of CO₂ gas.
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Question 2.
What are oxidising agents?
Answer:
The substance which are capable of adding oxygen to Others, such substances are known as oxidising agents. Example: Potassium permangnate (KMnO₄) and potassium dichromate (K₂Cr₂O₇) are oxidising alcohols to acids, that is, adding oxygen to the starting material.

Page 76.

Question 1.
Would you be able to check if water is hard by using a detergent?
Answer:
No, it is not possible to check that water is hard by using a detergent because detergent gives foam with hard water also and does not give any scum or precipitate.

Question 2.
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
Answer:
Agitation is required for washing of clothes after adding the soap so that molecules of soap can form micelles to remove spots of oil, dirt particles etc. Micelle helps in the removal of spots of oil and dirt particles so agitation of clothes by different means helps in the removal of dirt particles.

RBSE Class 10 Science Chapter 4 Carbon and Its Compounds Textbook Questions and Answers

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:
(b) 7 covalent bonds.

Question 2.
Butanone is a four carbon compound with the functional group:
(a) Carboxylic acid
(b) Aldehyde
(c) Ketone
(d) Alcohol.
Answer:
(c) 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:
(b) The fuel is not burning completely.

Question 4.
Explain the nature of the covalent bond using the bond formation in CH₃Cl.
Answer:
In case of carbon, it has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration. But this is not possible due to the high energy requirement for the carbon atom. Therefore, carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements.

Hence, covalent bonds are found in CH₃Cl. Carbon needs 4 electrons to complete its octet, while hydrogen requires one electron to achieve the noble gas configuration. Similarly, chlorine also requires one electron. That is why, they all share electrons, so that carbon forms three bonds with hydrogen and one bond with chlorine, as follows:

The type of bond in CH₃Cl is single covalent bond.

Question 5.
Draw the electron dot structures for:
(a) ethanoic acid
(b) H₂S
(c) propanone
(d) F₂.
Answer:
The electron dot structure of the compounds given above are as follows:
(a) Ethanonic acid:

(b) H₂S

(C) Propane

(d) F₂

Question 6.
What is a homologous series? Explain with example.
Answer:
Homologous series:
A series of compounds in which the same functional group substitutes the hydrogen present in a carbon chain is called homologous series. Chemical properties of all the members of a homologous series are same because functional group is same and chemical properties depends on functional group.
Example:
General formula of Alkane (Saturated Hydrocarbon) Homologous series is CnH₂n⁺. Methane (CH₄), Ethane (C₂H₆), Propane (C₃Hg), Butane (C₄H₁₀), Pentane.(C₅H₁₂) and Hexane (C₆H₁₄) etc. are the members of this series.

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Answer:
Difference in Ethanol (C₂H₅OH Ethyl Alcohol) and Ethanoic acid (CH₃ COOH Acetic Acid)
(a) On the basis of Physical Properties:
(i) Ethanol has smell like spirit while ethanoic acid has pungent smell.
(ii) The melting point and boiling point of ethanol are 156 and 351 K successively.
while the melting point and boiling point of pure ethanoic acid are 290 and 391 K.

(b) On the basis of Chemical Properties:
(1) Ethanol does not effect the blue litmus while ethanoic acid turns blue litmus into red.
(2) Ethanol does not react with Na₂CO₃ and NaHCO₃ while ethanoic acid forms salt, CO₂ and H₂O by the reaction with these compounds.

(iii) Ethanol forms sodium ethoxide by the reaction swith Na and hydrogen gas is liberated with effervescence while ethanoic acid forms sodium acetate (Sodium Ethanoate) by the reaction with Na.

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:
When soap is added in water then its two ends have differing properties, one is hydrophilic which dissolves in water, while the other end is hydrophobic, which dissolves in hydrocarbons not in water. When this is added in water ionic end of soap remains in water and the hydrocarbon ‘tail’ out of water. Inside water, these molecules have a unique orientation that keeps the hydrocarbon portion out of the water.

This is achieved by forming clusters of molecules in which the hydrophobic tails are in the inner side of the cluster and the ionic ends are on the surface of the cluster. This structure is called a micelle. Soap in the form of a micelle is able to clean, because the oily dirt is collected in the centre of the micelle. Soap is soluble insolvent like Ethanol so micelle will not form in such type of solvents.

Question 9.
Why are carbon and its compounds used as fuels for most applications.
Answer:
Carbon and its compounds are used as fuels due to following reasons:
(i) When carbon and its compounds are burned in presence of excess air or oxygen then large amount of heat and light is produced.
(ii) Once burned, they keep on burning without needing additional heat energy.
(iii) Calorific value of these is high.

Question 10.
Explain the formation of scum when hard water is treated with soap.
Answer:
When hard water is treated with soap, foam is formed with difficulty because soap forms insoluble salt by the reaction with calcium and magnesium salt present in hard water. This insoluble salts is called scum. In this situation large amount of soap is used to form the foam.

Question 11.
What change will you observe if you test soap with litmus paper (Red and Blue)?
Answer:
The soap solution is alkaline because it is the salt of weak acid and strong base so it turns red litmus into blue but it does not have any effect on blue litmus.

Question 12.
What is Hydrogenation? What is its industrial application?
Answer:
Addition of hydrogen to unsaturated hydrocarbons in presence of a catalyst such as nickel (Ni) or palladium (Pd) to give saturated hydrocarbons is called hydrogenation.

micelle. Soap in the form of a micelle is able to clean, because the oily dirt will be collected in the centre of the micelle. The micelles remains in solution as a colloid and will not come together to precipitate because of ion- ion repulsion. Thus, the dirt suspended in the micelles can be removed easily. The soap micelles are large enough to scatter light. So, a soap solution appears cloudy.