Carbon and its Compounds — Class 10 Science PYQs

The formula of functional group for aldehyde is :

Assertion (A) : Carbon shares its valence electrons with other atoms of carbon or with atoms of other elements.
Reason (R) : The shared electrons belong to the outermost shells of both the atoms and lead to both atoms attaining the noble gas configuration.

(a) (i) Give reasons for the following :
(I) Covalent compounds are poor conductor of electricity.
(II) Soap does not form lather in hard water.
(III) Carbon shows catenation but silicon does not.
(ii) Write chemical equations for the following :
(I) Oxidation of ethanol by acidified ${\mathrm{K}}_2\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7$.
(II) Hydrogenation of ethene.
OR
(b) Mohan heated ethanol with a compound 'X' in the presence of a few drops of conc. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ and observed a sweet smelling compound 'Y' is formed. When 'Y' is treated with sodium hydroxide it gives back ethanol and a compound 'Z'.
(i) Identify 'X', 'Y' and 'Z'.
(ii) Write the role of conc. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ in the reaction.
(iii) Write the chemical equations involved and name the reactions.

(a) (i) Draw two isomeric structures of Butene (${\mathrm{C}}_4{\mathrm{H}}_8$).
(ii) Name the following compounds :
(I) $\mathrm{H}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{Cl}$ ...
(II) $\mathrm{H}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{H}$ ...
(iii) Write the chemical equations for the following reactions. Mention one essential condition each for these reactions to take place.
(I) Ethanol undergoes complete oxidation
(II) Propene undergoes hydrogenation
(III) Ethanoic acid reacts with ethanol
OR
(b) (i) A carbon compound X is a good solvent. On reaction with sodium, X forms two products Y and Z. Z is used to convert vegetable oil into vegetable ghee. Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer.
(ii) Write chemical equation to show what happens when ethanol :
(I) burns in oxygen/air.
(II) is heated at $443\mathrm{K}$ in excess conc. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$.
(III) reacts with acidified potassium dichromate.

(a) A saturated organic compound 'A' with two carbon atoms belongs to the homologous series of alcohols. On oxidation, it forms an organic acid 'B' with molecular mass $60\mathrm{u}$. On heating 'A' with excess concentrated sulphuric acid at $443\mathrm{K}$, an unsaturated hydrocarbon 'C' is formed.
(i) Name A, B and C.
(ii) Calculate molecular mass of C.
(iii) What happens when a pinch of sodium carbonate is added to compound B ? Write chemical equation for the reaction.
(iv) Draw electron dot structure of compound B.
OR
(b) (i) What is a homologous series of carbon compounds ? Write the name and formula of three successive members of the homologous series of compounds having functional group – COOH.
(ii) Write the name of two carbon compounds in which carbon atoms are arranged in the form of a ring. Draw the structure of any one of the two.

(a) (i) Draw electron dot structure of chlorine molecule.
(Atomic Number of Chlorine = 17)
(ii) What happens when chlorine reacts with methane in the presence of sunlight ? Write the name of the reaction.
OR
(b) (i) Give reason why carbon forms compounds mainly by covalent bonding.
(ii) Why do covalent compounds have low melting and boiling points.
(iii) Give reason for the following :
I. Covalent compounds are bad conductors of electricity.
II. Carbon shows catenation.

Select from the following the members of same homologous series :
(1)
H H H
| | |
H - C - C - C = O
| |
H H
(2)
H H
| |
H - C - C - C - H
| || |
H O H
(3)
H H O
| | ||
H - C - C - C - OH
| |
H H
(4)
H H H H
| | | |
H - C - C - C - C = O
| | |
H H H
(b) What happens to (i) the melting point, and (ii) the solubility of compounds as the molecular mass of the compounds in a homologous series increases ?

Assertion (A) : Propanal and propanone are structural isomers.
Reason (R) : Propanal and propanone both have the same molecular formula.

What are micelles ? Draw the structure.

(a) (i) A compound 'X' having two carbon atoms in its molecule turns blue litmus red and 5 – 8% solution of 'X' in water is widely used as a preservative. Identify the compound 'X' and write its structure.
(ii) Compare its pH nature with a mineral acid.
(iii) 'X' on reacting with alcohols produces sweet smelling compounds, used in making perfumes. Name the reaction and write its chemical equation.
(iv) When sodium carbonate is added to 'X', a colourless gas is produced which turns lime water milky. Write the chemical equation for the reaction giving the name of the salt produced.
OR
(b) (i) Differentiate between saturated and unsaturated hydrocarbons by giving one example each, with a structural formula.
(ii) Write the method of converting an unsaturated hydrocarbon into a saturated hydrocarbon. Name the industry where this reaction is commonly used.
(iii) Write the name and structure of a hydrocarbon having double bond and four carbon atoms in its one molecule.