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NCERT solutions Chemistry Class 12 Part 1 chapter 2 Solutions

Chapters

NCERT Chemistry Class 12 Part 1

Chemistry Textbook for Class 12 Part 1

Chapter 2 - Solutions

Pages 37 - 55

Calculate the mass percentage of benzene (C6H6) and carbon tetrachloride (CCl4) if 22 g of benzene is dissolved in 122 g of carbon tetrachloride.

Q 1 | Page 37

Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.

Q 2 | Page 37

Calculate the molarity of each of the following solutions: (a) 30 g of Co(NO3)2. 6H2O in 4.3 L of solution (b)30 mL of 0.5 M H2SO4 diluted to 500 mL.

Q 3 | Page 37

Calculate the mass of urea (NH2CONH2) required in making 2.5 kg of 0.25 molal aqueous solution.

Q 4 | Page 37

Calculate (a) molality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL-1

Q 5 | Page 37

H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.

Q 6 | Page 41

Henry’s law constant for CO2 in water is 1.67 × 108 Pa at 298 K. Calculate the quantity of CO2 in 500 mL of soda water when packed under 2.5 atm CO2 pressure at 298 K

Q 7 | Page 41

The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the vapour phase.

Q 8 | Page 47

Vapour pressure of pure water at 298 K is 23.8 mm Hg. 50 g of urea (NH2CONH2) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

Q 9 | Page 55

Boiling point of water at 750 mm Hg is 99.63°C. How much sucrose is to be added to 500 g of water such that it boils at 100°C. Molal elevation constant for water is 0.52 K kg mol−1.

Q 10 | Page 55

Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in  75 g of acetic acid to lower its melting point by 1.5°C. Kf = 3.9 K kg mol−1.

Q 11 | Page 55

Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL of water at 37°C.

Q 12 | Page 55

Pages 59 - 62

Define the term solution

Q 1.1 | Page 59

How many types of solutions are formed? Write briefly about each type with an example.

Q 1.2 | Page 59

Give an example of solid solution in which the solute is a gas.

Q 2 | Page 59

Define Mole fraction

Q 3.1 | Page 59

Define Molarity (M)

Q 3.2 | Page 59

Define Mass percentage.

Q 3.3 | Page 59

Concentrated nitric acid used in laboratory work is 68% nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is 1.504 g mL−1?

Q 4 | Page 59

A solution of glucose in water is labelled as 10% w/w, what would be the molality and mole fraction of each component in the solution? If the density of solution is 1.2 g mL−1, then what shall be the molarity of the solution?

Q 5 | Page 60

How many mL of 0.1 M HCl are required to react completely with 1 g mixture of Na2CO3 and NaHCO3containing equimolar amounts of both?

Q 6 | Page 60

A solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass. Calculate the mass percentage of the resulting solution.

Q 7 | Page 60

An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H6O2) and 200 g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g mL−1, then what shall be the molarity of the solution?

Q 8 | Page 60

A sample of drinking water was found to be severely contaminated with chloroform (CHCl3) supposed to be a carcinogen. The level of contamination was 15 ppm (by mass):

(i) express this in percent by mass

(ii) determine the molality of chloroform in the water sample.

Q 9 | Page 60

What role does the molecular interaction play in a solution of alcohol and water?

Q 10 | Page 60

Why do gases always tend to be less soluble in liquids as the temperature is raised?

Q 11 | Page 60

The partial pressure of ethane over a solution containing 6.56 × 10−3 g of ethane is 1 bar. If the solution contains 5.00 × 10−2 g of ethane, then what shall be the partial pressure of the gas?

Q 13 | Page 60

What is meant by positive and negative deviations from Raoult's law and how is the sign of ΔsolH related to positive and negative deviations from Raoult's law?

Q 14 | Page 60

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 molar mass of the solute?

Q 15 | Page 60

Heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components are 105.2 kPa and 46.8 kPa respectively. What will be the vapour pressure of a mixture of 26.0 g of heptane and 35 g of octane?

Q 16 | Page 60

The vapour pressure of water is 12.3 kPa at 300 K. Calculate vapour pressure of 1 molal solution of a non-volatile solute in it.

Q 17 | Page 60

Calculate the mass of a non-volatile solute (molar mass 40 g mol−1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.

Q 18 | Page 60

A solution containing 30 g of non-volatile solute exactly in 90 g of water has a vapour pressure of 2.8 kPa at 298 K. Further, 18 g of water is then added to the solution and the new vapour pressure becomes 2.9 kPa at 298 K. Calculate:

(1) molar mass of the solute

(2) vapour pressure of water at 298 K.

Q 19 | Page 60

A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.

Q 20 | Page 60

Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g of benzene (C6H6), 1 g of AB2 lowers the freezing point by 2.3 Kwhereas 1.0 g of AB4 lowers it by 1.3 K. The molar depression constant for benzene is 5.1 Kkg mol−1. Calculate atomic masses of A and B.

Q 21 | Page 60

At 300 K, 36 g of glucose present in a litre of its solution has an osmotic pressure of 4.98 bar. If the osmotic pressure of the solution is 1.52 bars at the same temperature, what would be its concentration?

Q 22 | Page 61

Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane and explain. Cyclohexane, KCl, CH3OH, CH3CN.

Q 24 | Page 61

Amongst the following compounds, identify which are insoluble, partially soluble and highly soluble in water?

(i) phenol 

(ii) toluene 

(iii) formic acid

(iv) ethylene glycol 

(v) chloroform 

(vi) pentanol.

Q 25 | Page 61

If the density of some lake water is 1.25 g mL−1 and contains 92 g of Na+ ions per kg of water, calculate the molality of Na+ ions in the lake.

Q 26 | Page 61

If the solubility product of CuS is 6 × 10−16, calculate the maximum molarity of CuS in aqueous solution.

Q 27 | Page 61

Calculate the mass percentage of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 g of C9H8O4 is dissolved in 450 g of CH3CN.

Q 28 | Page 61

Nalorphene (C19H21NO3), similar to morphine, is used to combat withdrawal symptoms in narcotic users. Dose of nalorphene generally given is 1.5 mg. Calculate the mass of 1.5 × 10−3m aqueous solution required for the above dose.

Q 29 | Page 61

Calculate the amount of benzoic acid (C6H5COOH) required for preparing 250 mL of 0.15 M solution in methanol.

Q 30 | Page 61

The depression in freezing point of water observed for the same amount of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order given above. Explain briefly.

Q 31 | Page 61

Calculate the depression in the freezing point of water when 10 g of CH3CH2CHClCOOH is added to 250 g of water. Ka = 1.4 × 10−3K= 1.86 K kg mol−1.

Q 32 | Page 61

19.5 g of CH2FCOOH is dissolved in 500 g of water. The depression in the freezing point of water observed is 1.0°C. Calculate the van’t Hoff factor and dissociation constant of fluoroacetic acid.

Q 33 | Page 61

Vapour pressure of water at 293 Kis 17.535 mm Hg. Calculate the vapour pressure of water at 293 Kwhen 25 g of glucose is dissolved in 450 g of water.

Q 34 | Page 61

Henry’s law constant for the molality of methane in benzene at 298 Kis 4.27 × 105 mm Hg. Calculate the solubility of methane in benzene at 298 Kunder 760 mm Hg.

Q 35 | Page 61

100 g of liquid A (molar mass 140 g mol−1) was dissolved in 1000 g of liquid B (molar mass 180 g mol−1). The vapour pressure of pure liquid B was found to be 500 torr. Calculate the vapour pressure of pure liquid A and its vapour pressure in the solution if the total vapour pressure of the solution is 475 Torr.

Q 36 | Page 61

Vapour pressure of pure acetone and chloroform at 328 K are 741.8 mm Hg and 632.8 mm Hg respectively. Assuming that they form ideal solution over the entire range of composition, plot ptotalpchloroform’ and pacetone as a function of xacetone. The experimental data observed for different compositions of mixture is.

100 ×xacetone 0 11.8 23.4 36.0 50.8 58.2 64.5 72.1
pacetone /mm Hg 0 54.9 110.1 202.4 322.7 405.9 454.1 521.1
pchloroform/mm Hg 632.8 548.1 469.4 359.7 257.7 193.6 161.2 120.7
Q 37 | Page 62

Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at 300 K are 50.71 mm Hg and 32.06 mm Hg respectively. Calculate the mole fraction of benzene in vapour phase if 80 g of benzene is mixed with 100 g of toluene.

Q 38 | Page 62

The air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportion of 20% is to 79% by volume at 298 K. The water is in equilibrium with air at a pressure of 10 atm. At 298 Kif the Henry’s law constants for oxygen and nitrogen are 3.30 × 107 mm and 6.51 × 107 mm respectively, calculate the composition of these gases in water.

Q 39 | Page 62

Determine the amount of CaCl2 (= 2.47) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75 atm at 27°C.

Q 40 | Page 62

Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K2SO4 in 2 liter of water at 25° C, assuming that it is completely dissociated.

Q 41 | Page 62

NCERT Chemistry Class 12 Part 1

Chemistry Textbook for Class 12 Part 1
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