Grade 10 : Science - 4. Carbon Compounds (Set 3) | Concept of Maths

Question 1

A student attempts to analyze the electron dot structure of Ethyne ($C_2H_2$) but makes a conceptual statement regarding its covalent bonds. Identify the incorrect statement.

Accepted Answer

C) The total number of shared electron pairs (bonding pairs) in an ethyne molecule is 4.

Answer

A) There is a triple covalent bond between the two carbon atoms sharing 6 electrons.

Answer

B) Each hydrogen atom shares a single pair of electrons with a carbon atom.

Answer

D) The carbon-carbon and carbon-hydrogen bonds are arranged in a linear geometry.

Question 2

An organic compound X with the molecular formula $C_3H_6O_2$ reacts vigorously with sodium metal to evolve a colorless gas Y which burns with a pop sound. Compound X also reacts with solid sodium bicarbonate to produce gas Z which turns lime water milky. Identify the structural formula of X and the identities of gases Y and Z.

Accepted Answer

B) $X = CH_3CH_2COOH$, $Y = H_2$, $Z = CO_2$

Answer

A) $X = CH_3COOCH_3$, $Y = O_2$, $Z = CO_2$

Answer

C) $X = CH_3COCH_2OH$, $Y = H_2$, Z = CO

Answer

D) $X = CH_3CH_2COOH$, $Y = CO_2$, $Z = H_2$

Question 3

A mixture of ethanoic acid and ethanol is heated in the presence of concentrated $H_2SO_4$. The ester product formed is isolated and then heated with NaOH solution (saponification). Which of the following options correctly identifies the final salt and alcohol produced during this entire pathway?

Accepted Answer

A) Sodium ethanoate and Ethanol

Answer

B) Sodium acetate and Methanol

Answer

C) Ethyl ethanoate and Water

Answer

D) Sodium methanoate and Ethanol

Question 4

Consider the following statements about the structural isomers of Pentane ($C_5H_{12}$):
I. Isomers of pentane exhibit different chemical properties because they have completely different functional groups.
II. Neopentane (2,2-dimethylpropane) has a lower boiling point than n-pentane because its spherical shape reduces the surface area, weakening intermolecular Van der Waals forces.
III. The total number of unique structural chain isomers possible for pentane is 3.

Which of the statements given above are correct?

Accepted Answer

B) Only II and III

Answer

A) Only I and II

Answer

C) Only I and III

Answer

D) All I, II, and III

Question 5

A student tests the properties of soaps in different water samples. They add equal volumes of soap solution to three test tubes:
- Tube A: Distilled water
- Tube B: Tap water containing dissolved $Ca(HCO_3)_2$
- Tube C: Underground well water containing dissolved $MgSO_4$

Which of the following describes the accurate observation and underlying chemical reasoning?

Accepted Answer

C) Tubes B and C form a white curd-like precipitate (scum) because calcium and magnesium ions react with soap to form insoluble salts.

Answer

A) Tube A forms scum because distilled water lacks ions to stabilize soap micelle structures.

Answer

B) Tube B forms a rich lather immediately because bicarbonate ions enhance soap solubility.

Answer

D) Tube C forms lather while Tube B forms scum because sulfate ions do not interfere with soap molecules.

Question 6

In the homologous series of Alkynes, let $M_n$ represent the molar mass of the n-th member (where n = 1 corresponds to Ethyne, $C_2H_2$). Which of the following expressions correctly gives the difference in molar mass between the n-th and the (n+2)-th member of this series?

Accepted Answer

B) 28 u

Answer

A) 14 u

Answer

C) 42 u

Answer

D) 56 u

Question 7

Analyze the reaction pathway below:
$$Compound A (C_2H_6O) \xrightarrow{Conc. H_2SO_4, \, 443 K} Compound B (C_2H_4) \xrightarrow{H_2, \, Ni Catalyst} Compound C$$ Identify the IUPAC name and the nature of Compound C.

Accepted Answer

B) Ethane, which is a saturated hydrocarbon.

Answer

A) Ethene, which is an unsaturated hydrocarbon.

Answer

C) Ethanol, which is an alcohol.

Answer

D) Ethyne, which is an unsaturated hydrocarbon containing a triple bond.

Question 8

A student sets up an experiment to study esterification by mixing 1 mL of ethanoic acid and 1 mL of ethanol. They prepare four test tubes with different conditions:
- Tube 1: Added 2-3 drops of concentrated $H_2SO_4$.
- Tube 2: Added 2-3 drops of dilute HCl.
- Tube 3: Added 2-3 drops of concentrated NaOH.
- Tube 4: No catalyst added.

In which test tube will the sweet-smelling ester form fastest, and what is the chemical role of the agent responsible?

Accepted Answer

B) Tube 1; Concentrated $H_2SO_4$ acts as an acid catalyst to speed up the reaction and as a dehydrating agent to remove water, driving the reversible reaction forward.

Answer

A) Tube 3; NaOH acts as a strong base catalyst to neutralize carboxylic acids, shifting the reaction forward.

Answer

C) Tube 2; Dilute HCl provides hydration water molecules that stabilize the transition state of the ester.

Answer

D) Tube 4; The reaction is autocatalytic and proceeds fastest in neutral conditions without interference.

Question 9

A saturated straight-chain hydrocarbon 'P' contains exactly 10 covalent bonds in a single molecule. Identify the correct value of the number of carbon atoms (n) and the IUPAC name of compound 'P'.

Accepted Answer

A) n = 3, Propane

Answer

B) n = 3, Propene

Answer

C) n = 4, Butane

Answer

D) n = 4, Butyne

Question 10

A student writes the following chemical equation to represent the reaction of ethene with bromine water:
$$CH_2=CH_2 + Br_2 \xrightarrow{Sunlight} CH_3-CHBr_2$$ Identify the errors in this student's chemical formulation.

Accepted Answer

B) The reaction is an addition reaction that occurs readily without sunlight; the correct product is 1,2-dibromoethane ($CH_2Br-CH_2Br$).

Answer

A) The reaction is a substitution reaction and requires heating instead of sunlight; the product is correct.

Answer

C) The reaction is a dehydration reaction; the product must be ethyne (CH \equiv CH) and hydrogen bromide.

Answer

D) The reaction represents a catalytic reduction; it requires a platinum catalyst instead of sunlight.