SSLC Chemistry Annual Exam Answer Key

SSLC EXAMINATION, MARCH - 2025

CHEMISTRY (English)

Time: 1½ Hours

Total Score: 40

Instructions:

• The first 15 minutes is cool-off time.
• You may use this time to read the questions and plan your answers.
• Answer only on the basis of instructions and questions given.
• Consider score and time while answering.

SECTION - A

Answer any 4 questions from 1 to 5. Each question carries 1 score. 4x1=4

1. Which of the given compounds is a mineral of Aluminium?

(Calamine, Cuprite, Cryolite, Magnetite)

Answer - Cryolite

1

2. Which polymer is formed from isoprene?

Answer: Natural Rubber

1

3. Find the total number of atoms in 2 GMM water (H₂O).

Answer :
GMM (gram molecular mass) of water (H₂O) = 18g
1 molecule of H₂O contains 3 atoms (2 hydrogen + 1 oxygen)
mole of H₂Ocontains (6.022 × 1023) molecules

1

4. Which is the product obtained when SO₃ gas is dissolved in concentrated sulphuric acid?

Answer: Oleum (H₂S₃O₇)

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5. Many of the metals in ______ block are used as catalysts in petroleum industry.

(s, p, d, f)

Answer: d-block

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SECTION - B

Answer any 4 questions from 6 to 10. Each question carries 2 scores. 4x2=8

6. Classify the following compounds into alkanes, alkenes and alkynes.

C₂H₄, C₅H₁₂, C₃H₈, C₆H₁₂

Answer
Alkanes: C₅H₁₂(Pentane), C₃H₈(Propane)

Alkenes: C₂H₄ (Ethene), C₇H₁₂ (Heptene)

Alkynes: (None in the given list)

2

7. Two gases Oxygen and Nitrogen at STP are given.

(a) Calculate the number of molecules in 64 g of Oxygen.

Answer
Molecular mass of O₂ = 32g
1 mole of O₂ = 6.022 ×10 ²³ molecules
Moles in 64 g O₂ = 64/32 = 2 moles
Total molecules = 2 × 6.022 × 10 ²³ =1.204×10 ²⁴ molecules

(b) Calculate the mass of Nitrogen having the same volume as that of 64 g of Oxygen.

At STP, equal volumes of gases contain equal moles.

64 g of O₂2= 2 moles

For N₂ 2 moles = 2 x 28 g = 56 g

Answer: Mass of Nitrogen = 56 g

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8. Two reactions related to the extraction of metals are given. Among these reactions, identify calcination and roasting.

(a) Cu_₂S ore is converted to Cu₂O by heating.

Answer: Roasting (since Cu₂S reacts with oxygen)

b) Carbonates and hydroxides of metals decompose to form their oxides.

Answer: Calcination (since it involves thermal decomposition without oxygen)

9. Identify A and B.

(a) CH₃-OH + CO (A) (in presence of catalyst, high temperature & pressure)

Answer: A = CH₃COOH (Acetic Acid)

(b) CHCl₃ + Cl₂ → (B) + HCl

Answer: B = CCl₄ (Carbon Tetrachloride)