Bihar Board 12th Chemistry Objective Answers Chapter 2 Solutions

Bihar Board 12th Chemistry Objective Questions and Answers

Bihar Board 12th Chemistry Objective Answers Chapter 2 Solutions

Question 1.
Homogeneous mixture of two or more than two components is called
(a) solute
(b) solvent
(c) both (a) and (b)
(d) solution
Answer:
(d) solution

Question 2.
Which of the following is an example of gaseous solution ?
(a) Camphor is nitrogen gas
(b) Solution of hydrogen in palladium
(c) Chloroform mixed with nitrogen gas
(d) Both (a) and (c)
Answer:
(d) Both (a) and (c)

Question 3.
In amalgam of mercury with sodium, solvent is
(a) mercury
(b) sodium
(c) amalgam
(d) none of these
Answer:
(b) sodium

Question 4.
What is the mole fraction of glucose in 10% w/W ‘ glucose solution ?
(a) 01
(b) 0.02
(c) 0.03
(d) 0.04
Answer:
(a) 01
No. of moles of glucose = \(\frac{10}{180}\) = 0.0555 mol
No. of moles of water = \(\frac{90}{18}\) = 5 mol
Number of moles of solution = 5.0555 mol
Mole fraction of glucos
\(=\frac{\text { No. of moles of glucose }}{\text { No. of moles of solution }}=\frac{0.0555}{5.0555}=0.01\)

Question 5.
A solution is obtained by mixing 200 g of 30 % and 300 g of 20% solution by weight. What is the percentage of solute in the final solution ?
(a) 50%
(b) 28%
(c) 64%
(d) 24%
Answer:
(d) 24%
Solute in 200 g of 30% solution = 60 g
Solute in 300 g of 20% solution = 60 g
Total grams of solute = 120 g
Total grams of solution = 200 + 300 = 500 g
% of solute in the final solution = \(=\frac{120}{500} \times 100=24 \%\)

Question 6.
When 1.04 g of BaCl₂ is present in 10⁵ g of solution the concentration of solution is
(a) 104 ppm
(b) 10.4 ppm
(c) 0.0104 ppm
(d) 104 ppm
Answer:
(b) 10.4 ppm

Question 7.
What will be the mole fraction of ethanol in a sample of spirit containing 85% ethanol by mass ?
(a) 0. 69
(b) 0.82
(c) 0.85
(d) 0.60
Answer:
(a) 69

Question 8.
What is the molarity of a solution containing 10 g of NaOH in 500 mL of solution ?
(a) 25 mol L^-1
(b) 0.75 mol L^-1(c) 0.5 mol L^-1
(d) 1.25 mol L^-1Answer:
(c) 0.5 mol L^-1

Question 9.
What will be the molarity of 30 mL of 0.5 M H₂SO₄solution diluted to 500 mL ?
(a) 3 M
(b) 0.03 M
(c) 3 M
(d) 0.103 M
Answer:
(b) 0.03 M

NaCl → Na⁺ + Cl
No. of moles of Na⁺ ions = 0.025
No. of Na⁺ ions = 03325 x 6.023 x 10²³= 1.505 x 10²²

Question 10.
How many Na⁺ ions are present in 100 mL of 0.25 M of NaCl solution ?
(a) 025 x 10²³
(b) 1.505 x 10²²(c) 15 x 10²²
(d) 2.5 x 10²³Answer:
(b) 1.505 x 10²²

Question 11.
How many grams of NaOH are present in 250 mL of 0.5 M NaOH solution ?
(a) 32 g
(b) 3.8 g
(c) 5 g
(d) 0.5 g
Answer:
(c) 5 g

Question 12.
What will be the molality of a solution of glucose in water which is 10% w/W ?
(a) 01 m
(b) 0.617 m
(c) 0.668 m
(d) 1.623 m
Answer:
(b) 0.617 m
(b) Mass of solution = 100 g
Mass of glucose = 10 g, Mass of water = 90 g

Question 13.
The molality of 648 g of pure water is …………….
(a) 36 m
(b) 5 m
(c) 3.6 m
(d) 5.55 m
Answer:
(d) 5 m

Question 14.
What is the mass of urea required for making 2.5 kg of 0.25 molal aqueous solution ?
(a) 37 g
(b) 25 g
(c) 125 g
(d) 27.5 g
Answer:
(a) 37 g

Question 15.
The law which indicates the relationship between solubility of a gas in liquid and pressure is_____________
(a) Raoult’s law
(b) Henry’s law
(c) Lowering of vapour pressure
(d) van’t Hoff law
Answer:
(b) Henry’s law

Question 16.
H₂S is a toxic gas used in qualitative analysis. If solubility of H₂S in water at STP is 0.195 m, what is the value of K_h ?
(a) 0263 bar
(b) 69.16 bar
(c) 192 bar
(d) 282 bar
Answer:
(d) 282 bar

Question 17.
Henry’s law constant for molality of methane in benzene at 298 K is 4.27 x 10⁵ mm Hg. The mole fraction of methane in benzene at 298 K under 760 mm Hg is
(a) 1.78 x 10^-3
(b) 17.43
(c) 0.114
(d) 2.814
Answer:
(a) 1.78 x 10^-3(a) Accorading to Henry’s law P = K_fx

Question 18.
Partial pressure of a solution component is directly proportional to its mole fraction. This is known as
(a) Henry’s law
(b) Raoult’s law
(c) Distribution law
(d) Ostwald’s dilution law
Answer:
(b) Raoult’s law

Question 19.
Among the following substances the lowest vapour pressure is exerted by
(a) water
(b) alcohol
(c) ether
(d) mercury
Answer:
(d) mercury

Question 20.
Which of the following solutions shows positive deviation from Raoult’s law ?
(a) Acetone + Aniline
(b) Acetone + Ethanol
(c) Water + Nitric acid
(d) Chloroform + Benzene
Answer:
(b) Acetone + Ethanol

Question 21.
Which of the following solutions is an example of negative deviation from Raoult’s law ?
(a) Acetone + Ethanol
(b) Carbon tetrachloride + Chloroform
(c) Acetone + Chloroform
(d) Water + Ethanol
Answer:
(c) Acetone + Chloroform

Question 22.
The system that forms maximum boiling azeotrope is
(a) acetone – chloroform
(b) ethanol – acetone
(c) n-hexane – n-heptane
(d) carbon disulphide – acetone.
Answer:
(a) acetone – chloroform

Question 23.
An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling point of the solvent. What is the molecular mass of the solute ?
(a) 23.4 g mol^-1
(b) 41.35 g mol^-1(c) 10 g mol^-1
(d) 20.8 g mol^-1Answer:
(b) 41.35 g mol^-1Vapour pressure of pure water at boiling point = 1 atm = 1.013 bar
Vapour pressure of solution (p_s) = 1.004 bar
Let mass of solution = 100 g
Mass of solute = 2 g
Mass of solvent = 100 – 2 = 98 g

Question 24.
Sprinkling of salt helps in clearing the snow covered roads in hills. The phenomenon involved in the process is ………..
(a) lowering in vapour pressure of snow
(b) depression in freezing point of snow
(c) increase in freezing point of snow
(d) melting of ice due to increase in temperature by putting salt.
Answer:
(b) depression in freezing point of snow

Question 25.
What weight of glycerol should be added to 600 g of water in order to lower its freezing point by 10°C ?
(K_f= 1.86° Cm^-1)
(a) 496 g
(b) 297 g
(c) 310 g
(d) 426 g
Answer:
(b) 297 g

Question 26.
The osmotic pressure of a solution can be increased by
(a) increasing the volume
(b) increasing the number of solute molecules
(c) decreasing the temperature
(d) removing semipermeable membrane.
Answer:
(b) increasing the number of solute molecules

Question 27.
10% solution of urea is isotonic with 6% solution of a non-volatile solute X. What is the molecular mass of solute X ?
(a) 6 g mol^-1
(b) 60 g mol^-1(c) 36 g mol^-1
(d) 32 g mol^-1Answer:
(c) 36 g mol^-1

Question 28.
A solution containing 10.2 g glycerine per litre is isotonic , with a 2% solution of glucose. What is the molecular mass of glycerine ?
(a) 91.8 g
(b) 1198 g
(c) 83.9 g
(d) 890.3 g
Answer:
(a) 91.8 g

Question 29.
A plant cell shrinks when it is kept in a …………..
(a) hypotonic solution
(b) hypertonic solution
(c) isotonic solution
(d) pure water.
Answer:
(b) hypertonic solution

Question 30.
Why is the molecular mass determined by measuring colligative property in case of some solutes is abnormal ?
(a) Due to association or dissociation of solute molecules.
(b) Due to insolubility of solute molecules.
(c) Due to decomposition of solute molecules.
(d) Due to large size of solute molecules.
Answer:
(a) Due to association or dissociation of solute molecules.

Question 31.
Which of the following representations of i (van’t Hoff factor) is not correct ?

Answer:
(d)

Question 32.
Which of the following will have same value of van’t Hoff factor as that of K₄[Fe(CN)₆] ?
(a) Al₂(SO₄)
(b) AlCl
(c) Al(NO₃)₃
(d) Al(OH)₃Answer:
(a) Al₂(SO₄)

Question 33.
Which of the following has the highest freezing point ?
(a) 1m NaCl solution
(b) 1m KCl solution
(c) 1m AlCl₃ solution
(d) 1m C₆HpO₆ solution
Answer:
(d) 1m C₆HpO₆ solution

Question 34.
What will be the degree of dissociation of 0.1 M Mg(NO₃)₂ solution if van’t Hoff factor is 2.74 ?
(a) 75%
(b) 87%
(c) 100%
(d) 92%
Answer:
(b) 87%

Question 35.
What will be the freezing point of a 0.5 m KCl solution ? The molal freezing point constant of water is 1.86 °C m^-1.
(a) -1.86 °C
(b) -0.372 °C
(c) -3.2 °C
(d) 0°C
Answer:
(a) -1.86 °C

Question 36.
What amount of CaCl₂ (i = 2.47) is dissolved in 2 litres of water so that its osmotic pressure is 0.5 atm at 27 °C ?
(a) 3.42 g
(b) 9.24 g
(c) 2.834 g
(d) 1.820 g
Answer:
(d) 1.820 g

Question 37.
The van’t Hoff factor of 0.005 M aqueous solution of KCl is 1.95. The degree of ionisation of KCI is …………..
(a) 0.95
(b) 0.97
(c) 0.94
(d) 0.96
Answer:
(a) 0.95

Question 38.
At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is
(a) less than the rate of crystallisation
(b) greater than the rate of crystallisation
(c) equal to the rate of crystallisation
(d) zero
Answer:
(c) equal to the rate of crystallisation

Question 39.
Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon
(a) temperature
(b) nature of solute
(c) pressure
(d) nature of solvent
Answer:
(c) pressure

Question 40.
Low concentration of oxygen in the blood and tissues of people living at high altitude is due to_______________
(a) low temperature
(b) low atmospheric pressure
(c) high atmospheric pressure
(d) both low temperature and high atmospheric pressure
Answer:
(b) low atmospheric pressure

Question 41.
Which of the following aqueous solutions should have the highest boiling point ?
(a) 1.0 MNaOH
(b) 1.0 MNa₂SO₄(c) 1.0 MNH₄NO₃
(d) 1.0 MKNO₃Answer:
(a) 1.0 MNaOH

Question 42.
In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl₂ solution is
(a) the same
(b) about twice
(c) about three times
(d) about six times.
Answer:
(c) about three times

Question 43.
The values of van’t Hoff factors for KCI, NaCl and K₂SO₄, respectively, are_______________ .
(a) 2, 2 and 2
(b) 2, 2 and 3
(c) 1,1 and 2
(d) 1, 1 and 1
Answer:
(b) 2, 2 and 3

Question 44.
Value of Henry’s constant K_H _____________
(a) increases with increase in temperature
(b) decreases with increase in temperature
(c) remains constant
(d) first increases then decreases
Answer:
(a) increases with increase in temperature