Class 12 Important Questions for Chemistry – Solutions

NCERT Exemplar Class 12 Chemistry is very important resource for students preparing for XII Board Examination. Here we have provided NCERT Exemplar Problems Solutions along with NCERT Exemplar Problems Class 12.

Question from very important topics are covered by NCERT Exemplar Class 12. You also get idea about the type of questions and method to answer in your class 12th examination.

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Here you can get Class 12 Important Questions Chemistry based on NCERT Text book for Class XII. Chemistry Class 12 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Solutions for Class 12 Chemistry subject.

Chemistry Important Questions Class 12 are given below.

Multiple Choice Questions (Type-I)

  1. Which of the following units is useful in relating concentration of solution with its vapour pressure?
    • (i) mole fraction
    • (ii) parts per million
    • (iii) mass percentage
    • (iv) molality
  2. On dissolving sugar in water at room temperature solution feels cool to touch.
    Under which of the following cases dissolution of sugar will be most rapid?

    • (i) Sugar crystals in cold water.
    • (ii) Sugar crystals in hot water.
    • (iii) Powdered sugar in cold water.
    • (iv) Powdered sugar in hot water.
  3. At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is ____________.
    • (i) less than the rate of crystallisation
    • (ii) greater than the rate of crystallisation
    • (iii) equal to the rate of crystallisation
    • (iv) zero
  4. A beaker contains a solution of substance ‘A’. Precipitation of substance ‘A’ takes place when small amount of ‘A’ is added to the solution. The solution is _____________.
    • (i) saturated
    • (ii) supersaturated
    • (iii) unsaturated
    • (iv) concentrated
  5. Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon __________.
    • (i) Temperature
    • (ii) Nature of solute
    • (iii) Pressure
    • (iv) Nature of solvent
  6. Low concentration of oxygen in the blood and tissues of people living at high altitude is due to _____________.
    • (i) low temperature
    • (ii) low atmospheric pressure
    • (iii) high atmospheric pressure
    • (iv) both low temperature and high atmospheric pressure
  7. Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s law?
    • (i) Methanol and acetone.
    • (ii) Chloroform and acetone.
    • (iii) Nitric acid and water.
    • (iv) Phenol and aniline.
  8. Colligative properties depend on .
    • (i) the nature of the solute particles dissolved in solution.
    • (ii) the number of solute particles in solution.
    • (iii) the physical properties of the solute particles dissolved in solution.
    • (iv) the nature of solvent particles.
  9. Which of the following aqueous solutions should have the highest boiling point?
    • (i) 1.0 M NaOH
    • (ii) 1.0 M Na2SO4
    • (iii) 1.0 M NH4NO3
    • (iv) 1.0 M KNO3
  10. The unit of ebulioscopic constant is _______.
    • (i) K kg mol–1 or K (molality)–1
    • (ii) mol kg K–1 or K–1(molality)
    • (iii) kg mol–1 K–1 or K–1(molality)–1
    • (iv) K mol kg–1 or K (molality)
  11. In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl2 solution is _____.
    • (i) the same
    • (ii) about twice
    • (iii) about three times
    • (iv) about six times
  12. An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because .
    • (i) it gains water due to osmosis.
    • (ii) it loses water due to reverse osmosis.
    • (iii) it gains water due to reverse osmosis.
    • (iv) it loses water due to osmosis.
  13. At a given temperature, osmotic pressure of a concentrated solution of a substance .
    • (i) is higher than that at a dilute solution.
    • (ii) is lower than that of a dilute solution.
    • (iii) is same as that of a dilute solution.
    • (iv) cannot be compared with osmotic pressure of dilute solution.
  14. Which of the following statements is false?
    • (i) Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.
    • (ii) The osmotic pressure of a solution is given by the equation Π = CRT ( where C is the molarity of the solution).
    • (iii) Decreasing order of osmotic pressure for 0.01 M aqueous solutions of barium chloride, potassium chloride, acetic acid and sucrose is BaCl2 > KCl > CH3COOH > sucrose.
    • (iv) According to Raoult’s law, the vapour pressure exerted by a volatile component of a solution is directly proportional to its mole fraction in the solution.
  15. The values of Van’t Hoff factors for KCl, NaCl and K2 SO4 , respectively, are_________.
    • (i) 2, 2 and 2
    • (ii) 2, 2 and 3
    • (iii) 1, 1 and 2
    • (iv) 1, 1 and 1
  16. Which of the following statements is false?
    • (i) Units of atmospheric pressure and osmotic pressure are the same.
    • (ii) In reverse osmosis, solvent molecules move through a semipermeable membrane from a region of lower concentration of solute to a region of higher concentration.
    • (iii) The value of molal depression constant depends on nature of solvent.
    • (iv) Relative lowering of vapour pressure, is a dimensionless quantity.
  17. Value of Henry’s constant KH___________ .
    • (i) increases with increase in temperature.
    • (ii) decreases with increase in temperature.
    • (iii) remains constant.
    • (iv) first increases then decreases.
  18. The value of Henry’s constant KH is _______.
    • (i) greater for gases with higher solubility.
    • (ii) greater for gases with lower solubility.
    • (iii) constant for all gases.
    • (iv) not related to the solubility of gases.
  19. Consider the Fig. and mark the correct option.

    • (i) water will move from side (A) to side (B) if a pressure lower than osmotic pressure is applied on piston (B).
    • (ii) water will move from side (B) to side (A) if a pressure greater than osmotic pressure is applied on piston (B).
    • (iii) water will move from side (B) to side (A) if a pressure equal to osmotic pressure is applied on piston (B).
    • (iv) water will move from side (A) to side (B) if pressure equal to osmotic pressure is applied on piston (A).
  20. We have three aqueous solutions of NaCl labelled as ‘A’, ‘B’ and ‘C’ with concentrations 0.1M, 0.01M and 0.001M, respectively. The value of van’t Hoff factor for these solutions will be in the order .
    • (i) iA < iB < iC
    • (ii) iA > iB > iC
    • (iii) iA = iB = iC
    • (iv) iA < iB > iC
  21. On the basis of information given below mark the correct option.
    Information:
    (A) In bromoethane and chloroethane mixture intermolecular interactions of A–A and B–B type are nearly same as A–B type interactions.
    (B) In ethanol and acetone mixture A–A or B–B type intermolecular interactions are stronger than A–B type interactions.
    (C) In chloroform and acetone mixture A–A or B–B type intermolecular interactions are weaker than A–B type interactions.

    • (i) Solution (B) and (C) will follow Raoult’s law.
    • (ii) Solution (A) will follow Raoult’s law.
    • (iii) Solution (B) will show negative deviation from Raoult’s law.
    • (iv) Solution (C) will show positive deviation from Raoult’s law.
  22. Two beakers of capacity 500 mL were taken. One of these beakers, labelled as “A”, was filled with 400 mL water whereas the beaker labelled “B” was filled with 400 mL of 2 M solution of NaCl. At the same temperature both the beakers were placed in closed containers of same material and same capacity as shown in Fig.
    At a given temperature, which of the following statement is correct about the vapour pressure of pure water and that of NaCl solution.

    • (i) vapour pressure in container (A) is more than that in container (B).
    • (ii) vapour pressure in container (A) is less than that in container (B).
    • (iii) vapour pressure is equal in both the containers.
    • (iv) vapour pressure in container (B) is twice the vapour pressure in container (A).
  23. If two liquids A and B form minimum boiling azeotrope at some specific composition then .
    • (i) A–B interactions are stronger than those between A–A or B–B.
    • (ii) vapour pressure of solution increases because more number of molecules of liquids A and B can escape from the solution.
    • (iii) vapour pressure of solution decreases because less number of molecules of only one of the liquids escape from the solution.
    • (iv) A–B interactions are weaker than those between A–A or B–B.
  24. 4L of 0.02 M aqueous solution of NaCl was diluted by adding one litre of water. The molality of the resultant solution is .
    • (i) 0.004
    • (ii) 0.008
    • (iii) 0.012
    • (iv) 0.016
  25. 25. On the basis of information given below mark the correct option.
    Information : On adding acetone to methanol some of the hydrogen bonds between methanol molecules break.

    • (i) At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show positive deviation from Raoult’s law.
      • (ii) At specific composition methanol-acetone mixture forms maximum boiling azeotrope and will show positive deviation from Raoult’s law.
    • (iii) At specific composition methanol-acetone mixture will form minimum boiling azeotrope and will show negative deviation from Raoult’s law.
    • (iv) At specific composition methanol-acetone mixture will form maximum boiling azeotrope and will show negative deviation from Raoult’s law.
  26. KH  value for Ar(g), CO2 (g), HCHO (g) and CH4 (g) are 40.39, 1.67, 1.83×10–5 and 0.413 respectively.
    Arrange these gases in the order of their increasing solubility.

    • (i) HCHO < CH4 < CO2 < Ar
    • (ii) HCHO < CO2 < CH4 < Ar
    • (iii) Ar < CO2 < CH4 < HCHO
    • (iv) Ar < CH4 < CO2 < HCHO

Multiple Choice Questions (Type-II)

Note : In the following questions two or more options may be correct.

  1. Which of the following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent?
    (a) nature of solute (b) temperature (c) pressure

    • (i) (a) and (c) at constant T
    • (ii) (a) and (b) at constant P
    • (iii) (b) and (c) only
    • (iv) (c) only
  2. Intermolecular forces between two benzene molecules are nearly of same strength as those between two toluene molecules. For a mixture of benzene and toluene, which of the following are not true?
    • (i) Δmix H = zero
    • (ii) Δmix V = zero
    • (iii) These will form minimum boiling azeotrope.
    • (iv) These will not form ideal solution.
  3. Relative lowering of vapour pressure is a colligative property because __________.
    • (i) It depends on the concentration of a non electrolyte solute in solution and does not depend on the nature of the solute molecules.
    • (ii) It depends on number of particles of electrolyte solute in solution and does not depend on the nature of the solute particles.
    • (iii) It depends on the concentration of a non electrolyte solute in solution as well as on the nature of the solute molecules.
    • (iv) It depends on the concentration of an electrolyte or nonelectrolyte solute in solution as well as on the nature of solute molecules.
  4. Van’t Hoff factor i is given by the expression _______________.
  5. Isotonic solutions must have the same ______________.
    • (i) solute
    • (ii) density
    • (iii) elevation in boiling point
    • (iv) depression in freezing point
  6. Which of the following binary mixtures will have same composition in liquid and vapour phase?
    • (i) Benzene – Toluene
    • (ii) Water-Nitric acid
    • (iii) Water-Ethanol
    • (iv) n-Hexane – n-Heptane
  7. In isotonic solutions ________________.
    • (i) solute and solvent both are same.
    • (ii) osmotic pressure is same.
    • (iii) solute and solvent may or may not be same.
    • (iv) solute is always same solvent may be different.
  8. For a binary ideal liquid solution, the variation in total vapour pressure versus composition of solution is given by which of the curves?
  9. Colligative properties are observed when ___________.
    • (i) a non volatile solid is dissolved in a volatile liquid.
    • (ii) a non volatile liquid is dissolved in another volatile liquid.
    • (iii) a gas is dissolved in non volatile liquid.
    • (iv) a volatile liquid is dissolved in another volatile liquid.

Short Answer Type Questions

  1. Components of a binary mixture of two liquids A and B were being separated by distillation. After some time separation of components stopped and composition of vapour phase became same as that of liquid phase. Both the components started coming in the distillate. Explain why this happened.
  2. Explain why on addition of 1 mol of NaCl to 1 litre of water, the boiling point of water increases, while addition of 1 mol of methyl alcohol to one litre of water decreases its boiling point.
  3. Explain the solubility rule “like dissolves like” in terms of intermolecular forces that exist in solutions.
  4. Concentration terms such as mass percentage, ppm, mole fraction and molality are independent of temperature, however molarity is a function of temperature. Explain.
  5. hat is the significance of Henry’s Law constant K ?
  6. Why are aquatic species more comfortable in cold water in comparison to warm water?
  7. (a) Explain the following phenomena with the help of Henry’s law.
    (i) Painful condition known as bends.
    (ii) Feeling of weakness and discomfort in breathing at high altitude.
    (b) Why soda water bottle kept at room temperature fizzes on opening?
  8. Why is the vapour pressure of an aqueous solution of glucose lower than that of water?
  9. How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the phenomenon involved in the process.
  10. What is “semi permeable membrane”?
  11. Give an example of a material used for making semipermeable membrane for carrying out reverse osmosis.

Matching Type Questions

Note : In the following questions match the items given in Column I and Column II.

  1. Match the items given in Column I and Column II.
    Column I Column II
    (i) Saturated solution (a) Solution having same osmotic pressure at a given temperature as that of given solution.
    (ii) Binary solution (b) A solution whose osmotic pressure is less than that of another.
    iii) Isotonic solution (c) Solution with two components.
    iv) Hypotonic solution (d) A solution which contains maximum amount of solute that can be dissolved in a given amount of solvent at a given temperature.
    (v) Solid solution (e) A solution whose osmotic pressure is more than that of another.
    vi) Hypertonic solution (f) A solution in solid phase.
  2. Match the items given in Column I with the type of solutions given in Column II.
    Column I Column II
    (i) Soda water (a) A solution of gas in solid
    (ii) Sugar solution (b) A solution of gas in gas
    iii) German silver (c) A solution of solid in liquid
    iv) Air (d) A solution of solid in solid
    (v) Hydrogen gas in palladium (e) A solution of gas in liquid
    (f) A solution of liquid in solid
  3. Match the laws given in Column I with expresions given in Column II.
  4. Match the terms given in Column I with expressions given in Column II.

Assertion and Reason Type Questions

Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(i) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(ii) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(iii) Assertion is correct statement but reason is wrong statement. (iv) Assertion and reason both are incorrect statements.
(v) Assertion is wrong statement but reason is correct statement.

  1. Assertion : Molarity of a solution in liquid state changes with temperature.
    Reason : The volume of a solution changes with change in temperature.
  2. Assertion : When methyl alcohol is added to water, boiling point of water increases.
    Reason : When a volatile solute is added to a volatile solvent elevation in boiling point is observed.
  3. Assertion : When NaCl is added to water a depression in freezing point is observed.
    Reason : The lowering of vapour pressure of a solution causes depression in the freezing point.
  4. Assertion : When a solution is separated from the pure solvent by a semi- permeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.
    Reason : Diffusion of solvent occurs from a region of high concentration solution to a region of low concentration solution.

Long Answer Type Questions

  1. Define the following modes of expressing the concentration of a solution. Which of these modes are independent of temperature and why?
    • (i) w/w (mass percentage)
    • (ii) V/V (volume percentage)
    • (iii) w/V (mass by volume percentage)
    • (iv) ppm. (parts per million)
    • (v) x (mole fraction)
    • (vi) M (Molarity)
    • (vii) m (Molality)
  2. Using Raoult’s law explain how the total vapour pressure over the solution is related to mole fraction of components in the following solutions.
    • (i) CHCl3 (l) and CH2Cl2(l)
    • (ii) NaCl(s) and H2O (l)
  3. Explain the terms ideal and non-ideal solutions in the light of forces of interactions operating between molecules in liquid solutions.
  4. Why is it not possible to obtain pure ethanol by fractional distillation? What general name is given to binary mixtures which show deviation from Raoult’s law and whose components cannot be separated by fractional distillation. How many types of such mixtures are there?
  5. When kept in water, raisin swells in size. Name and explain the phenomenon involved with the help of a diagram. Give three applications of the phenomenon.
  6. Discuss biological and industrial importance of osmosis.
  7. How can you remove the hard calcium carbonate layer of the egg without damaging its semiprermiable membrane? Can this egg be inserted into a bottle with a narrow neck without distorting its shape? Explain the process involved.
  8. Why is the mass determined by measuring a colligative property in case of some solutes abnormal ? Discuss it with the help of Van’t Hoff factor.

Answers to Multiple Choice Questions

MCQ (Type I)
1. (i) 2. (iv) 3. (iii) 4. (ii) 5. (iii) 6. (ii)
7. (i) 8. (ii) 9. (ii) 10. (i) 11. (iii) 12. (iv)
13. (i) 14. (i) 15. (ii) 16. (ii) 17. (i) 18. (ii)
19. (ii) 20. (iii) 21. (ii) 22. (i) 23. (i) 24. (iv)
25. (ii) 26. (iii)
MCQ (Type II)
1. (i), (ii) 2. (iii), (iv) 3. (i), (ii) 4. (i), (iii) 5. (ii), (iii)
6. (ii), (iii) 7. (ii), (iii) 8. (i), (iv) 9. (i), (ii)

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