Carbon and its Compounds — Class 10 Science PYQs

(A) / Both A and R are true and R is the correct explanation of A.

(A) / Both A and R are true and R is the correct explanation of A. (1 Mark)

(a) (i)
(I) They do not give rise to charged particles/ ions. (1)
(II) Soap reacts with calcium and magnesium salts present in
hard water and forms insoluble substances called Scum. (1)
(III) C-C bonds are strong and stable whereas Si-Si bonds are
relatively weak. (1)
(ii) (I) $\ce{CH3CH2OH ->[acidified K2Cr2O7+heat] CH3COOH}$ (1)
(II) $\ce{CH2=CH2 + H2 ->[Ni] CH3-CH3}$ (1)

(a) (i) • The unique ability of carbon to form bonds with other atoms of carbon giving rise to large molecules. (1 Mark)
• Because of strong and stable C-C bond. (1 Mark)
(ii) • A group of organic compounds with the same functional group and similar chemical properties / Series of compounds in which the same functional group substitutes for Hydrogen in a carbon chain / Compounds having same general formula, successive member differ by $\ce{CH2}$ or 14u. (1 Mark)
• Example: - Methane-Ethane or any other. (1 Mark)
(iii) Because soap forms insoluble precipitates (scum) by reacting with calcium and magnesium salts present in hard water. (1 Mark)

(B)/ alkene
1
1

(B)/-CHO (1)

(B) / -COOH (1 Mark)

(a) (i)
u2022 A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain./ Can be represented by a single general formula and successive members differ by $\ce{-CH2}$ unit or 14u.
u2022 $\ce{C2H4}$ and $\ce{C4H8}$ belong to the same homologous series/ are alkenes.
(ii) (I) $\ce{CH3CH2OH + CH3COOH ->[Acid] CH3COOC2H5 + H2O}$
(II) $\ce{C2H5OH + 3O2 ->[Burning] 2CO2 + 3H2O}$ (balancing may be ignored)
(iii) The ionic end of soap interacts with water while the carbon chain interacts with oil/dirt. The soap molecules thus form a structure called micelle.

(i) Carbon cannot form $\ce{C^4+}$ cation because removal of four electrons is energetically not possible. Carbon cannot form $\ce{C^4-}$ anion because nucleus with six protons cannot hold ten electrons. (2 Marks)
(ii) • A series of compounds in which the same functional group substitutes for hydrogen in carbon chain is called a homologous series. (1 Mark)
• Because of higher molecular mass of $\ce{C4H10}$ than $\ce{C3H8}$ or $\ce{C2H6}$. (1 Mark)
(iii) Ethanoic acid / acetic acid / $\ce{CH3COOH}$ is formed /
$\ce{CH3-CH2OH ->[Alkaline KMnO4 + Heat][Or acidified K2Cr2O7 + Heat] CH3COOH}$ (1 Mark)

(D)/ $\ce{C4H8}$ and $\ce{C5H12}$ (1 Mark)

(D)/ Propyne (1 Mark)

(i) I. Propanal (1 Mark)
II. Propyne (1 Mark)
(ii) I. Ester group (1 Mark)
II. $\ce{CH3-COOH + CH3-CH2OH ->[Acid] CH3-C(=O)-O-CH2-CH3 + H2O}$ (1 Mark)
(iii) Soaps reacts with calcium and magnesium salts present in hard water to form scum (insoluble substance). (1 Mark)

(B)/ $\ce{C4H8}$

(C)/ $\ce{C3H8}$ (1 Mark)

(b) (i) (I) Propanone/acetone
(
frac{1}{2})
(II) Propyne
(
frac{1}{2})
(ii) Hydrogenation/addition reaction.
(1)
(iii) $\ce{C4H10}$ will have higher melting point, as it has a higher molecular mass than $\ce{C3H8}$ and Melting point increases with the increase in molecular mass.
(1)
(iv) Sodium ethoxide ($\ce{C2H5ONa}$) is formed and hydrogen gas is evolved / $\ce{2Na + 2CH3CH2OH -> 2CH3CH2O-Na+ + H2}$ (balancing may be ignored)
(1)
(v) $\ce{CH3COON C2H5 + NaOH -> CH3COONa + C2H5OH}$
(
frac{1}{2}+
frac{1}{2})

(i) I. Propanal (1 Mark)
II. Propyne (1 Mark)
(ii) I. Ester group (1 Mark)
II. $\ce{CH3-COOH + CH3-CH2OH ->[Acid] CH3-C(=O)-O-CH2-CH3 + H2O}$ (1 Mark)
(iii) Soaps reacts with calcium and magnesium salts present in hard water to form scum (insoluble substance). (1 Mark)

(a) •
ce{CH3-CH2-CH2-CH2OH} /
H H H H
H-C-C-C-C-O-H
H H H H
• Butanol (1/2)
(b) • Ethanol gets oxidised to form ethanoic acid. (1/2)
(c) • alkaline
ce{KMnO4}+heat
ce{CH3-CH2-OH -> CH3COOH} (1/2)
•
ce{CH3-COOH + CH3-CH2OH <=>[Acid] CH3-C-O-CH2-CH3 + H2O} (1)
• Esterification reaction. (1)
OR
(c) • Ethanol will get dehydrated to form ethene. (1/2)
• alkaline
ce{KMnO4}+heat
ce{CH3-CH2-OH -> CH3COOH} (1/2)
(Award full marks if equation is written with condition)
• Dehydrating agent/ Catalyst (1)

(i) X - $\ce{CH3COOH}$/ethanoic acid /acetic acid
$\frac{1}{2}$
Y - $\ce{CH3COOC2H5}$/$\ce{CH3COOCH2CH3}$/ ester/ ethyl ethanoate
$\frac{1}{2}$
Z - $\ce{CH3COONa}$/sodium ethanoate/sodium acetate
$\frac{1}{2}$
(ii) Catalyst / dehydrating agent
$\frac{1}{2}$
(iii)
$\ce{CH3-COOH + CH3-CH2OH <=>[Acid] CH3-C-O-CH2-CH3 + H2O}$
• Esterification reaction
$\frac{1}{2}$
• $\ce{CH3COOC2H5 + NaOH -> CH3COONa + C2H5OH}$
1
• Saponification reaction/ De-esterification reaction
$\frac{1}{2}$
5

(A) / tomato, curd, ant-sting (1 Mark)

(A)/ Both A and R is true and R is correct explanation of A.

(A) / The hydrophobic tail of the soap molecule is in the interior of the cluster, whereas hydrophilic end is on the surface of the cluster. (1 Mark)