CBSE Class 10 Science Carbon and its compounds Assignment Set 06

Question. Ethane, with the molecular formula \( \text{C}_2\text{H}_6 \) has
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.
Answer: (b) 7 covalent bonds.

Question. Butanone is a four-carbon compound with the functional group
(a) Carboxylic acid.
(b) Aldehyde.
(c) Ketone.
(d) Alcohol.
Answer: (c) Ketone.

Question. 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. The chemical reaction shows the addition of chlorine to methane in the presence of sunlight.
\( \text{CH}_4 + \text{Cl}_2 \rightarrow \text{X} \)
What is likely to be the product of the reaction represented by “X”?
(a) \( \text{CH}_4 + \text{H}_2\text{SO}_4 \)
(b) \( \text{CH}_3\text{Cl} + \text{HCl} \)
(c) \( \text{CHCl}_3 + \text{HCl} \)
(d) \( \text{CH}_3\text{Cl} + \text{H}_2\text{SO}_4 \)
Answer: (b) \( \text{CH}_3\text{Cl} + \text{HCl} \)

Question. When ethanol is oxidized using potassium dichromate and Sulphuric acid. Which option represents the product “X”?
\( \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{K}_2\text{Cr}_2\text{O}_7\text{ / }\text{H}_2\text{SO}_4} \text{X} \)
Ethanol
(a) \( \text{CH}_2\text{O} \)
(b) \( \text{CH}_3\text{CH} \)
(c) \( \text{CH}_3\text{H}_2\text{O} \)
(d) \( \text{CH}_3\text{COOH} \)
Answer: (d) \( \text{CH}_3\text{COOH} \)

Question. The chemical reaction shows the addition of chlorine gas to hydrocarbon in the presence of sunlight.
\( \text{CHCl}_3 + \text{Cl}_2 \rightarrow \text{CCl}_4 + \text{HCl} \)
How does chlorine react to a hydrocarbon compound in the presence of sunlight?
(a) It adds hydrogen into the compound
(b) It adds an oxygen atom into the compound
(c) It substitutes hydrogen atom from the compound
(d) It breaks double and triple bonds into a single bond
Answer: (c) It substitutes hydrogen atom from the compound

Question. A student studies that vinegar, which is a diluted form of ethanoic acid, freezes during winter. What does this suggest about the physical properties of pure ethanoic acid?
(a) It has a low boiling point
(b) It has a low melting point
(c) It has a very high boiling point
(d) It has a very high melting point
Answer: (b) It has a low melting point

Question. Which of the following is the molecular formula of Cyclobutane?
(a) \( \text{C}_4\text{H}_{10} \)
(b) \( \text{C}_4\text{H}_6 \)
(c) \( \text{C}_4\text{H}_8 \)
(d) \( \text{C}_4\text{H}_4 \)
Answer: (c) \( \text{C}_4\text{H}_8 \)

Question. A student studies that a soap molecule has two ends, one of which is an ionic end and the other is the carbonic chain. Which option explains the interaction of a soap molecule with oil?
(a) Ionic end of the soap interacts with the oil
(b) The closest end of the soap interacts with the oil
(c) Carbonic chain end of the soap interacts with the oil
(d) Ends of the soap randomly interact with the oil
Answer: (c) Carbonic chain end of the soap interacts with the oil

Question. Methane, ethane and propane are said to form a homologous series because all are-
(a) Hydrocarbons
(b) Saturated compounds
(c) Aliphatic compounds
(d) Differ from each other by a \( \text{CH}_2 \) group
Answer: (d) Differ from each other by a \( \text{CH}_2 \) group

Question. Following is (are) the property (ies) of ionic compounds.
(a) They have high melting and boiling points
(b) They conduct electricity in solution or in molten state
(c) Both (a) and (b)
(d) None of the options
Answer: (c) Both (a) and (b)

Question. The following image represents a carbon compound.

    H   H   O   H
    |   |  ||   |
H - C - C - C - C - H
    |   |       |
    H   H       H

Which functional group is present in the compound?
(a) Alcohol
(b) Aldehyde
(c) Carboxylic acid
(d) Ketone
Answer: (d) Ketone

Question. The following represents the formulae of a few hydrocarbon compounds.
(a) \( \text{C}_2\text{H}_2 \) (b) \( \text{C}_2\text{H}_4 \) (c) \( \text{C}_2\text{H}_6 \) (d) \( \text{C}_3\text{H}_4 \)
Which of these compounds can be classified as alkynes?
(a) Only (a)
(b) Only (b)
(c) Both (a) and (d)
(d) Both (b) and (c)
Answer: (c) Both (a) and (d)

Question. Which of the following is the molecular formula of cyclobutane?
(a) \( \text{C}_4\text{H}_{10} \)
(b) \( \text{C}_4\text{H}_6 \)
(c) \( \text{C}_4\text{H}_8 \)
(d) \( \text{C}_4\text{H}_4 \)
Answer: (c) \( \text{C}_4\text{H}_8 \)

Question. The number of isomers of pentane is
(a) 2
(b) 3
(c) 4
(d) 5
Answer: (b) 3

Assignments

Question. Give the names of the following functional groups:
(i) —OH (ii) –CHO (iii) —COOH
Answer: (i) Alcohol group (ii) Aldehydic group (iii) Carboxylic acid group

Question. Write the IUPAC names of the following compounds.
(A)

    H   H
    |   |
H - C - C - OH
    |   |
    H   H

(B)

    H   O   H
    |   ||  |
H - C - C - C - H
    |       |
    H       H

(C)

    H   O
    |   ||
H - C - C - O - H
    |
    H

Answer: (A) Ethanol (B) Propanone (C) Ethanoic acid.

Question. Vapours of a hydrocarbon were passed through bromine dissolved in carbon tetrachloride. The yellow colour of bromine got discharged? Predict the nature of the hydrocarbon.
Answer: The hydrocarbon is unsaturated. It is either an alkene or alkyne.

Question. What is the role of soap in cleansing of clothes?
Answer: Soap helps in forming a stable emulsion between oil drops carrying dirt particles and water. The emulsion is also known as micelle.

Question. Which organic compound is added to make ethanol unfit for drinking purposes? What is the name of the mixture formed?
Answer: Methanol which is highly poisonous is added in small amount to ethanol in order to make it unfit for drinking purposes. The mixture is called methylated spirit or denatured alcohol.

Question. Which element exhibits the property of catenation to maximum and why?
Answer: The element is carbon. This is because of very small size of carbon atom (77 pm) and high strength of \( \text{C—C} \) bond (355 kJ mol\(^{-1}\)).

Question. How will you convert Ethene into Ethanol? Give the chemical reaction involved.
Answer: Ethene is converted into ethanol by passing its vapours through water in the presence of Sulphuric acid. This reaction is called hydration of Ethene.
\( \text{H}_2\text{C} = \text{CH}_2 + \text{H}_2\text{O} \xrightarrow{\text{H}_2\text{SO}_4} \text{CH}_3\text{—CH}_2\text{—OH} \)

Question. Explain with the help of chemical equations, the following properties of carbon.
(i) Combustion
(ii) Oxidation.
Answer:
(i) \( \text{C}_2\text{H}_5\text{OH} + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O} \) (Combustion)
(ii) \( \text{C}_2\text{H}_5\text{OH} + \text{O}_2 \xrightarrow{\text{K}_2\text{Cr}_2\text{O}_7\text{ / }\text{H}_2\text{SO}_4} \text{CH}_3\text{COOH} + \text{H}_2\text{O} \) (Oxidation)

Question. Give a chemical test to distinguish between:
(i) Ethane and Ethene
(ii) Ethanol and ethanoic acid
(iii) Soaps and detergents.
Answer: (i) Ethene decolorizes the yellow colour of bromine water while ethane does not.
(ii) Ethanoic acid gives a brisk effervescence with sodium hydrogen carbonate while ethanol does not.
(iii) Soaps form curdy white precipitate or scum with hard water while detergents do not form any precipitate.

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. What is a homologous series? Which two of the following organic compounds belong to the same homologous?
\( \text{CH}_3 \), \( \text{C}_2\text{H}_6 \), \( \text{C}_2\text{H}_6\text{O} \), \( \text{C}_2\text{H}_6\text{O}_2 \), \( \text{CH}_4\text{O} \)
Answer: Homologous series is a series of organic compounds which has same functional group and similar chemical properties. Each member of this series differs by \( \text{—CH}_2\text{—} \) in its molecular formula and 14u in its molecular mass.
\( \text{CH}_4\text{O} \) (\( \text{CH}_3\text{OH} \)) and \( \text{C}_2\text{H}_6\text{O} \) (\( \text{C}_2\text{H}_5\text{OH} \)) belong to same homologous series.

Question. (i) An unknown compound has the smell of vinegar. Identify it.
(ii) What do we get when ethanoic acid reacts with ethanol in the presence of concentrated Sulphuric acid?
(iii) Give a test to identify the presence of ethanoic acid.
Answer: (i) The compound is ethanoic acid (\( \text{CH}_3\text{COOH} \)) also called acetic acid.
(ii) Ethyl ethanoate (\( \text{CH}_3\text{COOC}_2\text{H}_5 \)) is formed by esterification reaction. It has fruity smell.
(iii) Dip a strip of blue litmus paper in the solution of ethanoic acid. Its colour will change to red.

Very Short Answer Type Questions :

Question. What is meant by a sturated hydrocarbon?
Answer: Those hydrocarbons in w hich valency of carbon is satisfied by single bonds only are called sturated hydrocarbons.

Question. How many covalent bonds are there in a molecule of ethane (C₂H₆)?
Answer: There are 7 covalent bonds in a molecule of ethane.

Question. Which of the following hydrocarbons undergo addition reactions?
C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄.
Answer: Addition reaction takes place in unsaturated hydrocarbons.
Hence C₃H₆ and C₂H₂ are unsaturated hydrocarbons and will show addition reaction.

Question. Give two properties of ionic compounds.
Answer: (i) High melting point and high boiling point.
(ii) Can conduct electricity.

Question. A compound has a molecular formula C₂H₆O. It is used as a fuel. Name the compound and name its functional group.
Answer: C₂H₆O is an alcohol, i.e. ethanol C₂H₅OH
Functional group is —OH.

Question. Give the IUPAC name of acetic acid and propyl alcohol.
Answer: Acetic acid – Ethanoic acid
Propyl alcohol – Propanol

Question. What is catenation?
Answer: Carbon has the unique ability to form bonds with the other atoms of carbon which gives rise to large molecules. This property of self linking is called catenation.

Question. What is the melting point of acetic acid?
Answer: M.P. = 290 K.

Question. What is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds?
Answer: —CH₂— is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds.

Question. How can you obtain the following from pure ethanol:
(i) Ethene (ii) Ethanoic acid (iii) Ester?
Answer: (i) Ethene: Ethanol when heated with excess of concentrated sulphuric acid will form ethene.

Question. (a) What is a ‘homologous series’ of substances?
(b) In an organic compound, which parts largely determine its physical and chemical properties?
(c) Write a chemical equation to represent the reaction of ethanol with acidified solution of potassium dichromate.
Answer: (a) Homologous series is a series of organic compounds having same general formula, all members of the compounds show same chemical properties and slight gradation in physical properties.
(b) Functional group.

Short Answer Type Questions :

Question. Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene.
Answer: 

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

Question. Why does carbon forms large number of compounds?
Answer: Carbon forms large number of compounds because of tetravalency and catenation property.
Tetravalency – Carbon has valency 4, to attain noble gas configuration carbon share its valence electrons with other elements like hydrogen, chlorine, etc.
Catenation – Carbon also shows the property of self-linking in which it forms long, branched or cyclic chains to form large number of compounds.

Question. Complete and balance the following equations:
(a) CH₃CH₂OH + O₂ ⎯→
(b) Na + CH₃CH₂OH ⎯→
Answer: (a) 2CH₃CH₂OH + 6O₂ ⎯⎯→ 4CO₂ + 6H₂O + heat + light
(b) 2Na + 2CH₃CH₂OH ⎯⎯→ 2CH₃CH₂ONa + H₂

Question. Name the peculiar/specific chemical property exclusive in case of saturated hydrocarbons and unsaturated hydrocarbons.
Answer: Saturated hydrocarbons show substitution reaction in which hydrogen atom gets substituted by other elements or atoms. Unsaturated hydrocarbons show addition reaction, in which hydrogen atom gets added across the double bond or triple bond of the compound.

Question. Write the electron dot structure of ethene molecule (C₂H₄).
Answer: 

Question. What is ethanoic acid? Write the formula of the functional group present in this acid.
What special name is given to its 5 – 8% solution in water? How does ethanoic acid react with sodium carbonate? Write a chemical equation of the reaction and common name of the salt produced.
Answer: 

Question. Write the names and molecular formula of two organic compounds having functional r group suffixed as ‘-oic acid’. With the help of a balanced chemical equation and explain what happens when any one of them reacts with sodium hydroxide.
Answer: 

Question. What is a homologous series? Which two of the following organic compounds belong to the same homologous?
CH₃ ,C₂H₆, C₂H₆O, C₂H₆O₂,CH₄O
Answer: 

Question. Write the electron dot structure of ethane molecule (C₂H₆).
Answer: 

Question. Give reasons for the following:
(i) Element carbon forms compounds mainly by covalent bonding.
(ii) Diamond has a high melting point.
(iii) Graphite is a good conductor of electricity.
(iv) Acetylene bums with a sooty flame.
(v) Kerosene does not decolourise bromine water while cooking oils do.
Answer: (i) It is because carbon has four valence electrons, it cannot gain or lose four electrons because high energy is needed. It can only share four electrons.
(ii) It is due to strong covalent bonds and compact structure of diamond.
(iii) It is due to presence of free electrons in graphite because each carbon is linked to three more carbon atoms.
(iv) It is due to high percentage of carbon, it burns with sooty or smoky flame.
(v) Kerosene oil is mixture of saturated hydrocarbons therefore does not decolourise bromine water.

Question. (a) The structural formula of an ester is

Write the structural formula of the corresponding alcohol and the acid.
(b) (i) Mention the experimental conditions involved in obtaining ethene from ethanol.
(ii) Write the chemical equation for the above reaction.
(c) Explain the cleansing action of soap.
Answer: (a) CH₃COOH and CH₃CH₂OH
Ethanoic acid Ethanol
(b) (i) Ethanol when heated in presence of conc. H₂SO₄, it gets dehydrated to form ethene at 160°C – 170°C.
(c) Cleansing action of soap: Soap consists of two ends, long chain of hydrocarbon is called hydrophobic which repels water and attracts dirt and grease. The other end is hydrophilic which attracts water. (Img 44)
When soap is added to water it forms micelle structure as shown below.
The tail of the soap sticks to the dirt inwards and the head points outward. When water is agitated, the dirt sticks to more number of soap molecules. On lot of rinsing with water, the water washes away soap molecule with dirt attached to it.

Question. A student reports the police about the illegal vending of alcohol near his school. He also knew about denatured alcohol.
(a) What is denatured alcohol?
(b) What would happen if somebody consumes denatured alcohol?
(c) What value is reflected by a student who reported the matter to police?
Answer: (a) Denatured alcohol is ethanol when added with poisonous methanol or copper sulphate solution.
(b) On drinking denatured alcohol a person may die.
(c) Value reflected by student is society’s law and order.

Question. 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 are soaps not considered suitable for washing where water is hard?
Answer: oaps are sodium or potassium salts of fatty acids having — COONa group. Detergents are sodium or potassium salts of sulphonic acids having — SO3Na and — SO4Na group. Cleansing action of soap: Soap molecules consist of a large hydrocarbon tail which is hydrophobic (water-hating or water repelling) with a negatively charged head which is hydrophilic (water-loving) as shown in figure. img
When a soap is dissolved in water, the molecules associate together as clusters called micelles in which water molecules, being polar in nature, surround the ions and the hydrocarbon part of the molecule attracts grease, oil and dirt.

Question. (a) State two properties of carbon which lead to a very large number of carbon compounds.
(b) Why does micelle formation take place when soap is added to water? Why are micelles not formed when soap is added to ethanol?
Answer: (a) (i)-Catenation (ii) Tetravalency
(b) It is because large number of molecular ions of soaps get aggregated and form colloidal solution.
Soap has hydrophobic tail (hydrocarbon) which dissolves in hydrocarbon part and hydrophilic part dissolves in water. Ethanol is non-polar solvent therefore micelles are not formed because hydrocarbon part gets attracted towards ethanol and ionic end will not dissolve in alcohol.

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

Question. Write the name and molecular formula of an organic compound having its name suffixed with ‘-ol and having two carbon atoms in the molecule. With the help of a balanced chemical equation indicate what happens when it is heated with excess of r cone.H₂S0₄.
Answer: 

Question. (a) What is vinegar?
(b) Describe with a chemical equation, what happens when sodium hydrogen carbonate reacts with ethanoic acid. (AI CBSE 2009)
Answer: (a) The 5% – 10% aqueous solution of acetic acid is called vinegar.
(b) CH₃COOH + NaHCO₃ ⎯⎯→ CH₃COONa + H₂O + CO₂
Acetic acid Sodium acetate
Ethanoic acid reacts with sodium bicarbonate to produce brisk effervescence of CO2 gas and sodium acetate.

Question. (a) Write the names of the functional groups in: (Img 37)
(b) Describe a chemical test to distinguish between ethanol and ethanoic acid.
Answer: (a) (i) Ketone (ii) Aldehyde
(b) On adding Na₂CO₃/NaHCO₃, the test tube containing ethanoic acid produces brisk effervescence of CO2 gas. Alcohol will not show any reaction.
CH₃COOH + NaHCO₃ ⎯→ CH₃COONa + CO₂ + H₂O
C₂H₅OH + NaHCO₃ ⎯→ No reaction

Long Answer Type Questions :

Question. Draw the electron dot structure for
(a) ethanoic acid.
(b) H₂S.
(c) propanone.
(d) F₂.
Answer: The electron dot structure are as follows:

Question. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Answer: Physical Properties

Question. You are given balls and stick model of six carbon atoms and fourteen hydrogen atoms and sufficient number of sticks. In how many ways one can join the models of six carbon atoms and fourteen hydrogen atoms to form different molecules of C₆H₁₄.
Answer: There are five ways in which six carbons can be joined with 14 hydrogen atoms.  

Question. Complete the following chemical equations and write the chemical name of the products formed.   

Answer: 

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