Class 11 Chemistry Important Questions

Class 11 Chemistry Important Questions

INORGANIC CHEMISTRY

SET I

Generally one long question (10 marks) and one short question (5 marks) and few very short questions (2 marks) are asked from this portion along with their reactions which are listed in Q.no. 22, 23 and 25 of short questions mentioned below. Sample questions:

Q 1) Write the principle and self-explanatory diagram for the manufacture of sulphuric acid from pyrite ore by contact process. How would you show that sulphuric acid acts as:

a) an acid    b) a dehydrating agent

Write down the test reaction of sulphate ion in its aqueous solution. — — — — [6 + 2 + 2]

• First of all read question carefully, understand it and then write answer. This question requires principle and well labeled diagram only (i.e. procedure/process is not needed).
• In second portion of the question only 2 marks is given for (a) and (b) so write only one or two reactions to show each.

Q 2) Write balanced chemical equation for the preparation of ammonia by Haber’s process. How does ammonia react with:

a. sodium    b. chlorine    c. CuSO₄ — — — — — [5]

• This question requires balanced chemical reaction only (not more language of principle and procedure).

SET II

Usually one short question (5 marks) and few very short questions are asked from this portion. Sometimes long question (10 mark) is also asked from (ii) and (iii) along with reactions mentioned below in Q. no. 24 and 25 of short questions. Sample questions:

Q1) Write the chemical reaction for the laboratory preparation of H₂S gas. How does Kipp’s apparatus work to supply H₂S gas in salt analysis? — — — — [5]

• First portion requires only a chemical reaction of lab preparation (not principle, figure and procedure).
• Second portion requires the explanation on intermittent supply of H₂S gas by Kipp’s apparatus with figure.

Q 2) How is pure sulphur dioxide prepared in the laboratory? How does sulphur dioxide react with: a. acidified KMnO₄   b. HI   c. Potassium iodate.

How is bleaching action of SO₂ different from Cl₂? — — — — — [5 + 3 + 2]

• First portion requires all principle, figure and procedure for lab preparation.
• Last portion requires table containing differences between bleaching action of SO₂ and Cl₂.

Q 3) Give the laboratory method of preparation of carbon monoxide. Why is carbon monoxide extremely poisonous? — — — — [4 + 1]

Q 4) Give a balanced chemical reaction for the preparation of CO in the laboratory. Why is CO a harmful gas? — — — — [1 + 1]

• This question seems similar to the above question but it is a very short question. First portion requires reaction only for lab preparation of CO.

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Some important short questions from Inorganic chemistry (Non-metals)

1. What is nascent hydrogen? Mention an example to show nascent hydrogen is more powerful reducing agent than molecular hydrogen.

2. Name the isotopes of hydrogen. Which isotope is least abundant / radioactive?

3. Differentiate between ortho and para hydrogen.

4. Mention an important use of:

• Deuterated water (heavy water)
• Tritium
• Ozone
• Nascent hydrogen
• Deuterium

5. Write two examples of each:

• Amphoteric oxide
• Neutral oxide
• Peroxide
• Mixed oxide

6. How does formation of ozone take place in stratosphere? What is meant by tailing of mercury?

7. Why is water an excellent solvent for polar substances?

8. Explain why:

• Ammonia cannot be dried by passing through conc. H₂SO₄.
• Conc. HNO₃ is stored in dark bottle.
• Phosphorus is stored in water.
• Conc. H₂SO₄ is diluted by adding acid into water but not water into acid.
• H₂SO₄ always acts as an oxidizing agent but not reducing agent.

9. What is the laboratory test of:

• Nitrate ion (i.e. Nitric acid) (i.e. ring test)
• Cl⁻, Br⁻ and I⁻
• Sulphate ion (sulphuric acid)

10. What is aqua regia? Write its reaction with gold.

11. Compare the bleaching properties of Cl₂ and SO₂.

12. Give a chemical reaction for the preparation of HCl. Why HBr and HI cannot be prepared by treating conc. H₂SO₄ with bromide and iodide?

13. How does bromine / chlorine react with hot and conc. NaOH?

14. Why is CO extremely poisonous?

15. What is meant by allotropy? Which one is hardest allotrope and latest discovered allotrope of carbon? Write one use of each.

16. What happens when white phosphorus is heated with aqueous caustic soda? (i.e. preparation of phosphine).

17. Write molecular formula and one use of:

• Borax    • Hypo
• Boric acid    • Carborundum
• Silica gel

18. Why are noble gases chemically inert? Write two uses of noble gases.

19. What are the major pollutants for photochemical smog? Write its major effects.

20. How do oxides of sulphur (SO₂) and nitrogen responsible for acid rain? Write major effects of acid rain.

21. What is greenhouse effect? How does CFC deplete ozone layer?

22. Reaction of ammonia with:

• CO₂ gas    • Cl₂ gas
• CuSO₄ solution    • Na-metal    • CuO
• Mercurous nitrate / chloride paper

23. Reaction of nitric acid with:

• Zn    • Mg    • Cu
• Fe    • I₂    • P₄

24. Reaction of CO with:

• Ni    • Cl₂    • NaOH
• Water gas (CO + H₂) is heated over ZnO + Cu

25. Reaction to show that:

• H₂SO₄ as: (a) an acid (b) an oxidizing agent (c) dehydrating agent
• SO₂ as an oxidizing agent
• H₂S as: (a) a reducing agent (b) an analytical reagent

SET III

This set is from metals. Usually one long question (10 marks) is asked from (1) and (2) numbers along with their reactions mentioned below in no. 8, 9, 10 and 11 of short questions.

Sample question:

Q1) Explain the Castner-Kellner process for the manufacture of caustic soda. Why do alkali metals impart characteristic colour to flame? How does NaOH react with a) CO₂   b) Zn — — — — — — [6 + 2 + 2]

One short question (5 mark) is asked from (3).

Sample question:

Q2) Give the chemistry of plaster of Paris. — — — — — — [5]

• Write chemistry means write some preparation methods, properties (physical + chemical) and uses.

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Some important short questions from metals

1. “Every ore is a mineral but every mineral is not ore” – give reason.

2. Write differences with example between:

• Calcination and Roasting
• Pyrometallurgy and Electrometallurgy
• Flux and Slag

3. Write short note on:

• Froth flotation process
• Carbon reduction process
• Aluminothermite process

4. Explain why:

• Carbon reduction process is not applied for the extraction of alkali metals.
• Alkali metals impart characteristic colour to the flame.
• Sodium metal gets tarnished in air.
• Quick lime produces hissing sound when added into cold water.
• Sodium metal is kept in kerosene.
• Sodium fire in laboratory is not extinguished by adding water.

5. Define the terms:

• Dead burnt plaster
• Setting of plaster of Paris

6. Write important characteristics of alkali metals and alkaline earth metals.

7. Write molecular formula and one use of: washing soda, baking soda, caustic soda and soda ash.

8. Convert:

• Caustic soda to washing soda and baking soda
• Sodium into washing soda
• Sodium into sodium silicate
• Washing soda into soda ash

9. Action of sodium (Na) with:

• Water    • NH₃
• Moist air

10. Action of caustic soda (NaOH) with:

• Phosphorus    • CO₂
• Sulphur    • Zinc
• Ammonium chloride

11. Action of washing soda (Na₂CO₃) with:

• Air    • Heated sand (SiO₂)
• Heat    • CaCl₂

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ORGANIC CHEMISTRY

SET IV

One short question (5 Marks) is asked out of two lab preparations mentioned in no. 1. Sample questions:

Q1) How is ethene prepared in the laboratory? What happens when ethene is passed through Baeyer’s reagent? — — — — — — — [4 + 1]

One short question (5 marks) is asked from no. 2, 3, 4 and 5. Usually one question is asked from Lassaigne’s test for nitrogen and Homologous series. Sample questions:

Q2) Define homologous series. What are the characteristic features of homologous series? Write structural formula and IUPAC name of first member of ketone series. — — — — [1 + 3 + 1]

Q3) Write short note on Lassaigne’s test for nitrogen. — — — — — — [5]

Q4) Write short note on:

a. Markovnikov’s rule    b. Ozonolysis — — — — — — — [5]

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Some important short questions from Organic chemistry

1. Explain why:

• Sodium extract (Lassaigne’s extract) is alkaline in nature.
• Sodium extract is boiled with conc. nitric acid while testing for halogens.

2. Give the functional isomers of: a) C₃H₈O   b) C₃H₆O   c) C₃H₆O₂ and write their IUPAC name.

3. What are electrophiles and nucleophiles? Write two examples of each.

4. Define inductive effect and give its important application.

5. Define antiknocking agent (Gasoline additive) and write one example.

6. What is the function of TEL in gasoline?

7. Define octane number. A fuel has octane number 80. What does it mean?

8. What is cracking of petroleum?

9. What happens when:

• Bromoethane is heated with sodium metal in presence of dry ether.
• Sodium acetate (sodium ethanoate) is heated with soda-lime.
• 2-Bromopropane is heated with alc. KOH.
• Ethene (ethylene) is passed through Baeyer’s reagent (Alkaline solution of KMnO₄).
• Ethyne (acetylene) gas is passed through ammoniacal solution of silver nitrate.

10. Write one example of each:

• Kolbe’s reaction
• Dehydrohalogenation reaction
• Decarboxylation reaction

11. Write a chemical test to distinguish:

• Ethyne (alkyne) from ethene (alkene)
• Ethene / ethyne from ethane

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PHYSICAL CHEMISTRY

SET V

This set is from physical chemistry. Usually one long question (10 marks) and one or two short questions (5 marks) and some very short questions are asked from this portion along with numerical problems. Sample questions:

Q 1) State and explain Graham’s law of diffusion of gas. Give its an application. 0.23 g of a volatile liquid occupies 126.4 cc at 27 °C and 760 mmHg pressure. Calculate the molecular weight of the liquid. How many molecules of the liquid are present in 0.23 g? — — [5 + 1 + 4]

Q 2) State Avogadro’s Law. Using the law, apply the law to deduce relationship between molecular mass and vapour density. — — — — — — — [5]

Q 3) 17 g of ammonia is completely reacted with 45 g of oxygen to produce NO and H₂O.

• Which is limiting reagent? — — — — — [5]
• Calculate the number of moles of unreacted reactant left over.
• What volume of NO is produced at NTP?
• Calculate the mass of water produced.

SET VI

This set is also from physical chemistry. Usually two short (5 marks) and few very short (2 marks) questions are asked from no. 1 – 8 of this set. Sample questions:

Q 1) Write short note on Le Chatelier’s principle. — — — [5]

Q 2) Write down the essential postulates of Bohr’s atomic model. How did it overcome the limitations of Rutherford’s atomic model? — — — [5]

Q 3) Give values of all four quantum numbers of 11^th electron of Magnesium (atomic no. 12). — — [2]

One short question is asked from no. 9 of this set. Sample question:

Q 4) Distinguish between oxidant and reductant. Balance the following reaction by oxidation number or ion-electron method:

MnO₄⁻ + H₂O₂ → MnO₂ + O₂ + OH⁻ — — — — [5]

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Some important short questions from Physical chemistry

1. What is ideal gas? Under what conditions will a gas nearly behave like an Ideal gas?

2. Why is Hund’s rule called rule of maximum multiplicity?

3. Define the terms: a. Surface tension   b. Viscosity   c. Aqueous tension

4. Give proper reason for the following:

• Rain (liquid) drops are spherical.
• Alcohol can flow easily but honey cannot.
• Evaporation takes place from the surface of liquid.
• It is more efficient to wash clothes in hot water than cold water.

5. What is evaporation? How does it differ from boiling?

6. Distinguish between:

• Isotropic and anisotropic substances giving an example of each
• Crystalline and amorphous solid
• Crystal lattice and unit cell

7. Mention one important character and an example of each:

• Efflorescence (efflorescent substance)
• Deliquescence (deliquescent substance)
• Hygroscopy (hygroscopic substance)

8. Why does electron not jump into the nucleus?

9. Define (a) nuclear fusion (b) nuclear fission (c) thermonuclear reaction, giving one example of each.

10. Distinguish between:

• Nuclear reactions and chemical reactions
• Controlled nuclear fission and uncontrolled nuclear fission

11. What is hydrogen bond? Differentiate between intramolecular and intermolecular H-bonding with example.

12. Define dipole moment and give its two important applications.

13. Write down the Lewis structure of:

• (NH₄)₂SO₄    • H₂SO₄, etc.

14. Differentiate between polar and non-polar covalent bonds with one example of each.

15. State modern periodic law. On what basis does Mendeleev’s periodic law differ from modern periodic law?

16. What is periodicity and its causes? How do atomic radii (size) vary in a group and a period?

17. State and explain the law of equivalent proportion / reciprocal proportion / multiple proportion.

18. Define the terms:

• Oxidation   • Oxidation number (state)
• Reduction   • Oxidant / reductant

19. What is redox reaction? Show that oxidation and reduction take place simultaneously.

20. Calculate the weight of 11.2 litres of CO₂ gas at STP.

21. Define equilibrium constant (K_c). Write the relation between K_p and K_c for the following reaction:

22. How do increase in temperature and pressure affect the equilibrium of the following reaction: