Chemistry MCQ for Class 12 Solutions – Free !

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Chemistry MCQ for Class 12 Solutions : Chapterwise Multiple Choice Questions with Answers for Class 12th Chemistry.

Chemistry MCQ for Class 12 Solutions

1.The molality of pure water is
(a) 55.5
(b) 50.5
(c) 18
(d) 60.5

2. The number of moles of NaCl in 3 litres of 3M solution is
(a) 1
(b) 3
(c) 9
(d) 27

3. 4L of 0.02 M aqueous solution of NaCl was diluted by adding one litre of water. The molality of the resultant solution is ________ .[NCERT Exemplar]
(a) 0.004
(b) 0.008
(c) 0.012
(d) 0.016

4. Low concentration of oxygen in the blood and tissues of people living at high altitude is due to _________ .[NCERT Exemplar]
(a) low temperature
(b) low atmospheric pressure
(c) high atmospheric pressure
(d) both low temperature and high atmospheric pressure

5. Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult’s law? [NCERT Exemplar]
(a) Methanol and acetone.
(b) Chloroform and acetone.
(c) Nitric acid and water.
(d) Phenol and aniline.

6. Which of the following aqueous solutions should have the highest boiling point? [NCERT Exemplar]
(a) 1.0 M NaOH
(b) 1.0 M Na2SO4
(c) 1.0 M NH4NO3
(d) 1.0 M KNO3

7. In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl2 solution is _________ . [NCERT Exemplar]
(a) the same
(b) about twice
(c) about three times
(d) about six times

8. An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because _________ . [NCERT Exemplar]
(a) it gains water due to osmosis.
(b) it loses water due to reverse osmosis.
(c) it gains water due to reverse osmosis.
(d) it loses water due to osmosis.

9. Which of the following statements is false? [NCERT Exemplar]
(а) Two different solutions of sucrose of same molality prepared in different solvents will have the same depression in freezing point.
(b) The osmotic pressure of a solution is given by the equation π = CRT (where C is the molarity of the solution).
(c) 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.
(d) 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.

10. The value of Henry’s constant KH is _________ .[NCERT Exemplar]
(а) greater for gases with higher solubility.
(b) greater for gases with lower solubility.
(c) constant for all gases.
(d) not related to the solubility of gases.

11. 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 __________ . [NCERT Exemplar]
(a) iA < iB < iC
(b) iA > iB > iC
(c) iA = iB = iC
(d) iA < iB > iC

12. A solution containing 10 g per dm3 of urea (molar mass 60 g mol-1) is isotonic with 5% solution of non-volatile solute, MB of solute is
(a) 300 g mol-1
(b) 350 g mol-1
(c) 200 g mol-1
(d) 250 g mol-1

13. Cone. H2SO4 is 98 % H2SO4 by mass has d = 1.84 g cm-3. Volume of acid required to make one litre of 0.1 M H2SO4 is
(a) 5.55 mL
(b) 10 mL
(c) 20 mL
(d) 30 mL

14. What is mole fraction of solute in 1.00 m aqueous solution?
(a) 0.0354
(b) 0.0177
(c) 0.177
(d) 1.770

15. When 1 mole of benzene is mixed with 1 mole of toluene (vapour pressure of benzene – 12.8 kPa, Toluene = 3.85 kPa)
(a) The vapour will contain equal amount of benzene and toluene.
(b) Not enough information is given for prediction.
(c) The vapour will contain a higher percentage of benzene.
(d) The vapour will contain higher percentage of toluene.

16. At 100°C, the vapour pressure of a solution of 6.5 g of solute in 100 g of water is 732 mm. If Kb is 0.52 K/m, the boiling point of solution will be [HOTS]
(a) 102°C
(b) 103°C
(c) 101 °C
(d) 100°C

17. Which of the following is incorrect for an ideal solution?
(a) ∆Hmix =0
(b) ∆Vmix = 0
(c) ∆P = Pobs – Pcalculated = 0
(d) ∆Gmix = 0

18. If molality of dilute solution is doubled, the value of molal depression constant (Kf) will be
(a) halved
(b) tripled
(c) unchanged
(d) doubled

19. The temperature at which 10% aqueous solution of (W/V) of glucose will show the osmotic pressure of 16.4 atom is (R = 0.082 L atom K-1 mol-1)
(a) 360°C
(b) 180 K
(c) 300 K
(d) 360 K

20. Which has the highest freezing point?
(a) 1 M glucose
(b) 1 M NaCl
(c) 1 M CaCl2
(d) 1 M AlF3

21 The boiling point of an azeotropic mixture of water and ethanol is less than that of water and ethanol. The mixture shows
(a) no deviation from Raoult’s Law.
(b) positive deviation from Raoult’s Law.
(c) negative deviation from Raoult’s Law.
(d) that the solution is unsaturated.

22. Which has the lowest boiling point at 1 atm pressure?
(a) 0.1 M KCl
(b) 0.1 M Urea
(c) 0.1 M CaCl2
(d) 0.1 M A1Cl3

23. Osmotic pressure of a solution is 0.0821 atm at a temperature of 300 K. The concentration in moles/litre will be
(a) 0.33
(b) 0.666
(c) 0.3 × 10-2
(d) 3

24. People add sodium chloride to water while boiling eggs. This is to
(a) decrease the boiling point.
(b) increase the boiling point.
(c) prevent the breaking of eggs.
(d) make eggs tasty.

25. The van’t Hoff factor (i) accounts for
(a) degree of solubilisation of solute.
(b) the extent of dissociation of solute.
(c) the extent of dissolution of solute.
(d) the degree of decomposition of solution.

26.The molal elevation constant depends upon
(a) nature of solute.
(b) nature of the solvent.
(c) vapour pressure of the solution.
(d) enthalpy change.

 

 

 

 

Answer:

  1. Answer: a
    Explaination:
    (a) Molality = Number of moles/kg of solvent
  2. Answer: c
    Explaination:
    (c) 3M solution means 3 moles in 1 litre.
    ∴ 9 moles in 3 litre.
  3. Answer: d
    Explaination:
    (d) M1V1 = M2V2
    0.02 × 4 = M2 × (4 + 1)
    ⇒ M2 = 0.016
  4. Answer: b
    Explaination:
    (b) Low atmospheric pressure will lead to low concentration of oxygen blood.
  5. Answer: a
    Explaination:
    (a) CH3OH and acetone, on mixing force of attraction will decrease. A mixture of methanol / ethanol and water shows positive deviation from Raoult’s law. The intermolecular forces present are weaker than those present in the ideal solution. The total vapour pressure of the solution is greater than the total vapour pressure of an ideal solution. Also, the vapour pressure of each component is greater than that predicted from Raoult’s law. Positive deviation:  When the cohesive forces between like molecules are greater than the adhesive forces between dissimilar molecules, the dissimilarities of polarity leads both components to escape solution more easily. Therefore, the vapor pressure is greater than expected from the Raoult’s law, showing positive deviation. If the deviation is large, then the vapor pressure curve shows a maximum at a particular composition and form a positive azeotrope. Some mixtures in which this happens are (1) benzene and methanol, (2) carbon disulfide and acetone, (3) chloroform and ethanol, and (4) glycine and water. When these pairs of components are mixed, the process is endothermic reaction as weaker intermolecular forces are formed so that ΔmixH is positive.
  6. Answer: b
    Explaination:
    (b) Because i = 3, ∆Tb ∝ i, Boiling point ∝ ∆Tb.
  7. Answer: c
    Explaination:
    (c) It will be nearly 3 times because number of particles in MgCl2 → Mg2+ + 2Cl are thrice than glucose.
  8. Answer: b
    Explaination:
    (d) Concentrated salt solution is hypertonic solution, therefore, fluids inside mango will come out and it shrivels.
  9. Answer:
    Explaination:
    (a) is false because ∆Tf will depend upon nature of solvent and their Kf.
  10. Answer:
    Explaination:
    (b) Higher the value of KH, lower will be solubility.
  11. Answer: c
    Explaination:
    (c) van’t Hoff factor (i) does not depend upon concentration.
  12. Answer: a
    Explaination:
    (a) \frac{1}{60}=\frac{5}{x}
    ⇒ x = 300 g mol-1
    1000 cm3 contains 10 g
    100 cm3 contains 1 g, i.e., 1%.
  13. a
  14. b
  15. Answer: c
    Explaination:
    (c) It is because benzene has high vapour pressure, it will form more vapours as compared to toluene.
  16. Answer: c
  17. Answer: d
    Explaination:
    (d) ∆G cannot be equal to zero because mixing does not lead to equilibrium.
  18. Answer: c
    Explaination:
    (c) Kf does not depend upon ‘mMt depends upon nature of solvent.
  19. Answer: d
    Explaination:
  20. Answer: a
    Explaination:
    (a) 1 M glucose solution has highest freezing point because it has lowest ∆Tf because i = l.
  21. b
  22. b
  23. c
  24. b
  25. b
  26. b

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