📘 UNIT – 2 CHEMISTRY (1 Mark Questions with Answers)

🧮 1. Define Mole
A mole is the quantity of substance that contains 6.022 × 10²³ particles (atoms, molecules or ions). It relates the mass of a substance to the number of particles present.
Formula: n=wGMWn = \frac{w}{GMW}.

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⚪ 2. What are Colloids?
Colloids are heterogeneous mixtures where very small particles of one substance remain evenly distributed in another. These particles are bigger than molecules but too small to settle down.

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🌱 3. Define an Ecosystem
An ecosystem is a biological system where living organisms (plants, animals, microbes) interact with each other and with their physical environment like air, water, and soil.

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⚠️ 4. What is Threshold Limit Value (TLV)?
TLV is the maximum concentration of a chemical substance to which a person can be exposed daily without harmful health effects. It ensures safe working conditions.

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💧 5. Explain Solvent and Solute with Example

  • Solvent → The substance present in larger quantity, in which other substances dissolve (e.g., water).

  • Solute → The substance present in smaller quantity that dissolves in the solvent (e.g., salt in water).

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🧂 6. Equivalent Weight of Na₂SO₄
Molecular weight of Na₂SO₄ = 142 g. Since it gives 2 equivalents (Na⁺ ions), the equivalent weight = 142 ÷ 2 = 71 g

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📏 7. Define Molarity
Molarity (M) is the number of moles of solute dissolved per litre of solution. It is a unit to express the concentration of a solution.

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⚗️ 8. Weight of 2 Moles of H₂SO₄
Molecular weight of H₂SO₄ = 98 g. Therefore, weight of 2 moles = 2 × 98 = 196 g.

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🥤 9. Solute and Solvent in Soda Water
In soda water, CO₂ gas acts as the solute, while water is the solvent. Together, they form a fizzy drink

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🔵 10. What is a Colloid?
A colloid is a special type of mixture where one substance is dispersed evenly throughout another, and the particles do not settle even on standing.

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🧊 11. Define Solubility
Solubility is the maximum amount of solute that can dissolve in a fixed quantity of solvent at a particular temperature to form a stable solution.

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🧪 12. What is Saturated Solution?
A saturated solution is one in which the solvent has dissolved the maximum possible amount of solute at that temperature. Extra solute remains undissolved.

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🧪 13. What is Unsaturated Solution?
An unsaturated solution is one that can still dissolve more solute at a given temperature. It means the solvent has not yet reached its maximum solubility.

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📏 14. Molarity Relation for Volumetric Analysis
In volumetric analysis, the relation used is:

M1V1=M2V2M_1 V_1 = M_2 V_2

where MM = molarity and VV = volume of solutions. This helps in neutralization and titration calculations.

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⚪ 15. What is Meant by Internal Phase of Colloids?
The internal phase of a colloid is the dispersed phase (tiny particles) that remain distributed throughout the external medium. Example: Fat globules in milk.

Chemistry 3 Mark Answers

1. Classify solutions based on their physical state.

  • Solutions are classified based on the physical state of the solvent.

  • The three main types of solutions are:

  • Gaseous Solutions: The solvent is a gas.

  • Example: Air (oxygen and other gases dissolved in nitrogen gas).

  • Liquid Solutions: The solvent is a liquid.

  • Example: Sugar dissolved in water (solid in liquid).

  • Solid Solutions: The solvent is a solid.

  • Example: Alloys like brass (zinc dissolved in copper).

2. Compare any three properties of lyophilic and lyophobic colloids.

  • Interaction:

  • Lyophilic: Strong interaction between dispersed phase and medium.

  • Lyophobic: Weak interaction between dispersed phase and medium.

  • Stability:

  • Lyophilic: Highly stable; not easily coagulated.

  • Lyophobic: Less stable; can be easily coagulated.

  • Reversibility:

  • Lyophilic: Reversible; residue can be easily reconverted.

  • Lyophobic: Irreversible; residue cannot be easily reconverted.

3. Explain the terms producers, consumers and decomposers with example.

  • Producers (Autotrophs): Make their own food (e.g., Sunlight, CO₂).

  • Example: Green plants, algae.

  • Consumers (Heterotrophs): Depend on others for food.

  • Example: Herbivores (cow), Carnivores (lion), Omnivores (humans).

  • Decomposers: Break down dead organic matter and waste.

  • Example: Bacteria and fungi.

4. Explain the effect of e-waste on environment.

  • Soil and Water Pollution: Toxic metals (lead, mercury) leach into soil and groundwater, contaminating them.

  • Air Pollution: Burning e-waste to recover metals releases toxic fumes and particulate matter into the air.

  • Health Hazards: These pollutants enter the food chain and water sources, posing serious health risks to animals and humans.

5. What are the saturated, Unsaturated and Super-saturated solutions?

  • Saturated Solution: A solution that contains the maximum amount of solute that can be dissolved at a given temperature.

  • Unsaturated Solution: A solution that contains less solute than the maximum amount that can be dissolved at a given temperature.

  • Supersaturated Solution: An unstable solution that contains more solute than the saturated solution at a given temperature. It crystallizes upon disturbance.

6. What is Molarity? Calculate molarity of a solution prepared by dissolving 5.85 g NaCl in 500 ml of water?

  • Molarity (M) is defined as the number of moles of solute dissolved per liter of solution.

  • Formula: Molarity (M) = Moles of Solute / Volume of Solution in Liters

  • Calculation:

  • Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol

  • Moles of NaCl = Mass / Molar mass = 5.85 g / 58.5 g/mol = 0.1 mol

  • Volume of solution = 500 mL = 500/1000 = 0.5 L

  • Molarity (M) = 0.1 mol / 0.5 L = 0.2 M

7. Write the formulae for the calculation of equivalent weight of acid, base and salt.

  • For an Acid: Equivalent Weight = Molar Mass of Acid / Basicity (Number of H⁺ ions it can provide)

  • Example: HCl (Basicity=1), H₂SO₄ (Basicity=2)

  • For a Base: Equivalent Weight = Molar Mass of Base / Acidity (Number of OH⁻ ions it can provide)

  • Example: NaOH (Acidity=1), Ca(OH)₂ (Acidity=2)

  • For a Salt: Equivalent Weight = Molar Mass of Salt / Total positive charge on cation (or negative charge on anion)

  • Example: NaCl (Charge=1), CaCl₂ (Charge=2), AlCl₃ (Charge=3)



Chemistry 5 Mark Answers

1. Find the weight of H₂SO₄ required to prepare 400 ml of 0.5 M solution.

To find the weight, we first calculate the number of moles required using the formula for molarity.

  • Moles of solute = Molarity × Volume in Liters = 0.5 mol/L × 0.4 L = 0.2 mol.

  • The molar mass of H₂SO₄ is 98 g/mol.

  • Therefore, Weight = Moles × Molar mass = 0.2 mol × 98 g/mol = 19.6 grams.

2. Find the normality of 500 ml solution containing 0.53 grams of Na₂CO₃.

Normality is calculated using the number of gram equivalents.

  • The molar mass of Na₂CO₃ is 106 g/mol. Its n-factor is 2.

  • Equivalent weight = Molar mass / n-factor = 106 / 2 = 53 g/equiv.

  • Number of gram equivalents = Mass / Equivalent weight = 0.53 g / 53 g/equiv = 0.01 equiv.

  • Volume of solution = 500 mL = 0.5 L.

  • Normality (N) = Gram equivalents / Volume(L) = 0.01 equiv / 0.5 L = 0.02 N.

3. What is Biodiversity? Explain the methods of Conservation of Biodiversity.

  • Biodiversity refers to the variety of life found on Earth, encompassing all species of plants, animals, and microorganisms, the genetic differences among them, and the ecosystems they form.

  • Methods of Conservation:

    • In-situ Conservation: This method involves protecting species in their natural habitats. Examples include establishing national parks, wildlife sanctuaries, and biosphere reserves.

    • Ex-situ Conservation: This method involves protecting endangered species by removing them from their natural habitat and placing them in a special care setting. Examples include zoos, botanical gardens, and seed banks.

    • Other crucial methods include enacting and enforcing environmental protection laws and raising public awareness about the importance of conservation.

4. What is Green chemistry? Explain any four principles of Green Chemistry.

  • Green Chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.

  • Four Principles of Green Chemistry:

    1. Prevention: It is better to prevent waste from being formed in the first place than to clean it up after.

    2. Atom Economy: Synthetic methods should be designed to ensure that the final product contains the maximum proportion of the starting materials, minimizing waste.

    3. Less Hazardous Chemical Syntheses: Chemical processes should be designed to use and generate substances that have little or no toxicity to human health and the environment.

    4. Design for Degradation: Chemical products should be designed to break down into harmless substances at the end of their life cycle so they do not accumulate in the environment.

5. What is Normality? Find the normality of a solution prepared by dissolving 1.58g of KMnO₄ in 200 ml of water? (GMW of KMnO₄ is 158g).

  • Normality (N) is defined as the number of gram equivalents of solute per litre of solution.

  • For KMnO₄ in acidic medium, the n-factor is 5.

  • Equivalent weight = Molar mass / n-factor = 158 g/mol / 5 = 31.6 g/equiv.

  • Number of gram equivalents = Mass / Equivalent weight = 1.58 g / 31.6 g/equiv = 0.05 equiv.

  • Volume of solution = 200 mL = 0.2 L.

  • Normality (N) = 0.05 equiv / 0.2 L = 0.25 N.

6. Calculate molarity and normality of a solution prepared by dissolving 10.6 g of Na₂CO₃ in 2 litres of water.

  • Molar mass of Na₂CO₃ = 106 g/mol.

  • Molarity Calculation:

    • Moles of Na₂CO₃ = 10.6 g / 106 g/mol = 0.1 mol.

    • Molarity (M) = Moles / Volume(L) = 0.1 mol / 2 L = 0.05 M.

  • Normality Calculation:

    • The n-factor for Na₂CO₃ is 2.

    • Normality (N) = Molarity × n-factor = 0.05 M × 2 = 0.1 N.

7. Find the weight of H₂SO₄ required to prepare 1 lit. of 0.2 N solution.

  • Normality (N) = Gram equivalents / Volume(L)

  • So, Gram equivalents needed = N × V = 0.2 N × 1 L = 0.2 equiv.

  • Equivalent weight of H₂SO₄ = Molar mass / n-factor = 98 g/mol / 2 = 49 g/equiv.

  • Therefore, Weight = Gram equivalents × Equivalent weight = 0.2 equiv × 49 g/equiv = 9.8 grams.


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