# 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
(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)
(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
(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
(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%
(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
(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
(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-1
(c) 0.5 mol L-1

Question 9.
What will be the molarity of 30 mL of 0.5 M H2SO4 solution diluted to 500 mL ?
(a) 3 M
(b) 0.03 M
(c) 3 M
(d) 0.103 M
(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 1023
(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
(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
(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
(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
(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
(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 Kh ?
(a) 0263 bar
(b) 69.16 bar
(c) 192 bar
(d) 282 bar
(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
(a) 1.78 x 10-3
(a) Accorading to Henry’s law P = Kx

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
(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
(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
(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
(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.
(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-1
(b) 41.35 g mol-1
Vapour pressure of pure water at boiling point = 1 atm = 1.013 bar
Vapour pressure of solution (ps) = 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.
(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 ?
(Kf = 1.86° Cm-1)
(a) 496 g
(b) 297 g
(c) 310 g
(d) 426 g
(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.
(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-1
(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
(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.
(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.
(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 ?

(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)3
(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
(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%
(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
(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
(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
(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
(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
(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
(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 MKNO3
(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

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
(b) 2, 2 and 3

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