CBSE 12 Chemistry Question Paper-2018 by Pavan | Practice Test to Test Your Knowledge
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  3. CBSE 12 Chemistry Question Paper-2018
CBSE 12 Chemistry Question Paper-2018

CBSE 12 Chemistry Question Paper-2018

This mock test includes actual CBSE Class 12 Chemistry board exam questions from the year 2018, helping students understand exam trends and practice real paper format

2025-08-05
Pavan Pavan
CBSE Class 12 Chemistry 2018 Grade 12

Duration

30 min

Questions

30

Marking

Negative

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Questions Preview

Analysis shows that FeO has a non-stoichiometric composition with the formula Fe0·95O. Give reason.

A
FeO contains iron in two oxidation states.
B
FeO contains excess oxygen atoms.
C
FeO contains a deficiency of oxygen atoms.
D
FeO is an unstable compound.

Out of chlorobenzene and benzyl chloride, which one gets easily hydrolyzed by aqueous NaOH and why?

A
Chlorobenzene
B
Benzyl chloride
C
Both react equally
D
Neither reacts

Write the coordination number and oxidation state of Platinum in the complex [Pt(en)2Cl2].

A
Coordination number: 4, Oxidation state: +2
B
Coordination number: 6, Oxidation state: +2
C
Coordination number: 4, Oxidation state: +4
D
Coordination number: 6, Oxidation state: +4

What is the IUPAC name of the following compound?

A
2-ethyl-3-methylpentan-2-ol
B
3-ethyl-2-methylpentan-2-ol
C
2-methyl-3-ethylpentan-2-ol
D
3-methyl-2-ethylpentan-2-ol

CO (g) and H2 (g) react to give different products in the presence of different catalysts. Which ability of the catalyst is shown by these reactions?

A
Catalytic activity
B
Selectivity
C
Inertness
D
Stability

Among the hydrides of Group-15 elements, which one has the lowest boiling point?

A
NH3
B
PH3
C
AsH3
D
SbH3

Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol–1) in 250 g of water. (Kf of water = 1·86 K kg mol–1)

A
-0.56°C
B
-1.12°C
C
-0.94°C
D
-1.05°C

How do you convert Ethanal to Propanone?

A
Oxidation
B
Reduction
C
Hydrolysis
D
Dehydration

Complete and balance the following chemical equation: Fe2+ + MnO4- + H+ → ?

A
Fe3+ + Mn2+ + H2O
B
Fe3+ + Mn2+ + OH-
C
Fe2+ + Mn3+ + H2O
D
Fe3+ + MnO2 + H2O

Calculate the rate of disappearance of N2O5 (g) for the reaction 2N2O5 (g) → 4NO2 (g) + O2 (g), given the rate of formation of NO2 is 2.8 × 10–3 M s–1.

A
5.6 × 10–3 M s–1
B
1.4 × 10–3 M s–1
C
2.8 × 10–3 M s–1
D
7.0 × 10–3 M s–1

Give reasons for the following:
(a) Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.
(b) Aquatic animals are more comfortable in cold water than in warm water.
(c) Elevation of boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.

A
All reasons are explained by colligative properties.
B
Osmotic pressure depends on the solute particle count, while boiling point elevation is a different concept.
C
The behavior is governed by vapor pressure lowering and freezing point depression.
D
All reasons are due to the interaction of solute particles with solvents.

An element ‘X’ (At. mass = 40 g mol–1) having f.c.c. structure, has unit cell edge length of 400 pm. Calculate the density of ‘X’ and the number of unit cells in 4 g of ‘X’. (NA = 6·022 × 10^23 mol–1)

A
Density: 4.5 g/cm³, Unit cells: 1.2 × 10^22
B
Density: 8.5 g/cm³, Unit cells: 2.4 × 10^22
C
Density: 7.2 g/cm³, Unit cells: 3.1 × 10^22
D
Density: 9.1 g/cm³, Unit cells: 4.2 × 10^22

Write the chemical reactions involved in the process of extraction of Gold. Explain the role of dilute NaCN and Zn in this process.

A
NaCN forms a complex with gold ions, and Zn reduces it to metallic gold.
B
NaCN dissolves gold, and Zn acts as a catalyst in the reaction.
C
NaCN removes impurities from gold, and Zn is used to purify the final product.
D
NaCN dissolves gold, and Zn aids in the filtration process.

Write the coordination number and oxidation state of Platinum in the complex [Pt(en)2Cl2].

A
Coordination number: 4, Oxidation state: +2
B
Coordination number: 6, Oxidation state: +2
C
Coordination number: 4, Oxidation state: +4
D
Coordination number: 6, Oxidation state: +4

What happens when a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount of FeCl3 solution?

A
The precipitate dissolves to form a complex solution.
B
The precipitate becomes insoluble.
C
The solution becomes turbid.
D
The precipitate is reduced to Fe2+.

Write the hybridisation and number of unpaired electrons in the complex [CoF6]3–. (Atomic No. of Co = 27)

A
Hybridisation: sp3d2, Unpaired electrons: 0
B
Hybridisation: sp3d2, Unpaired electrons: 1
C
Hybridisation: d2sp3, Unpaired electrons: 2
D
Hybridisation: sp3, Unpaired electrons: 2

Identify the chiral molecule in the following pair: (A) and (B) are two molecules. Which is chiral?

A
Molecule A is chiral.
B
Molecule B is chiral.
C
Neither molecule is chiral.
D
Both molecules are chiral.

Write the structure of the alkene formed by dehydrohalogenation of 1-bromo-1-methylcyclohexane with alcoholic KOH.

A
Cyclohexene
B
1-Methylcyclohexene
C
1,2-Dimethylcyclohexene
D
Trans-1,2-dimethylcyclohexene

What is the role of NaCN in the extraction of gold?

A
NaCN reacts with gold to form a soluble complex.
B
NaCN reduces gold ions to metallic gold.
C
NaCN stabilizes the gold metal.
D
NaCN acts as a catalyst in the reaction.

Write the formula for the coordination compound Iron(III) hexacyanoferrate(II).

A
[Fe(CN)6]3–
B
[Fe(CN)6]2–
C
[Fe(CN)6]4–
D
[Fe(CN)6]5–

Why is bithional added to soap?

A
It acts as an antibacterial agent.
B
It provides a pleasant fragrance.
C
It helps in moisturizing the skin.
D
It acts as a preservative.

What is tincture of iodine? Write its one use.

A
It is a solution of iodine in alcohol, used as a disinfectant.
B
It is a solution of iodine in water, used as an antiseptic.
C
It is a solution of iodine in glycerol, used as a preservative.
D
It is a solution of iodine in oil, used as a treatment for skin conditions.

Among the following, which one acts as a food preservative? Aspartame, Aspirin, Sodium Benzoate, Paracetamol

A
Aspartame
B
Aspirin
C
Sodium Benzoate
D
Paracetamol

Define polysaccharides with an example.

A
Polysaccharides are long-chain carbohydrates formed by the polymerization of simple sugars, e.g., starch.
B
Polysaccharides are short-chain carbohydrates formed by the condensation of glucose, e.g., glucose.
C
Polysaccharides are simple sugars that provide energy, e.g., fructose.
D
Polysaccharides are lipids that store energy, e.g., triglycerides.

What happens when a freshly prepared precipitate of Fe(OH)3 is shaken with a small amount of FeCl3 solution?

A
The precipitate dissolves to form a complex solution.
B
The precipitate becomes insoluble.
C
The solution becomes turbid.
D
The precipitate is reduced to Fe2+.

Write the hybridisation and number of unpaired electrons in the complex [CoF6]3–. (Atomic No. of Co = 27)

A
Hybridisation: sp3d2, Unpaired electrons: 0
B
Hybridisation: sp3d2, Unpaired electrons: 1
C
Hybridisation: d2sp3, Unpaired electrons: 2
D
Hybridisation: sp3, Unpaired electrons: 2

Identify the chiral molecule in the following pair: (A) and (B) are two molecules. Which is chiral?

A
Molecule A is chiral.
B
Molecule B is chiral.
C
Neither molecule is chiral.
D
Both molecules are chiral.

Write the structure of the alkene formed by dehydrohalogenation of 1-bromo-1-methylcyclohexane with alcoholic KOH.

A
Cyclohexene
B
1-Methylcyclohexene
C
1,2-Dimethylcyclohexene
D
Trans-1,2-dimethylcyclohexene

What is the role of NaCN in the extraction of gold?

A
NaCN reacts with gold to form a soluble complex.
B
NaCN reduces gold ions to metallic gold.
C
NaCN stabilizes the gold metal.
D
NaCN acts as a catalyst in the reaction.

Write the formula for the coordination compound Iron(III) hexacyanoferrate(II).

A
[Fe(CN)6]3–
B
[Fe(CN)6]2–
C
[Fe(CN)6]4–
D
[Fe(CN)6]5–