Lecture 5: Revison

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.

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.

Discuss biological and industrial importance of osmosis.

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.

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?

Explain the terms ideal and non-ideal solutions in the light of forces of
interactions operating between molecules in liquid solutions.

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) (v) x (mole fraction)
(ii) V/V (volume percentage) (vi) M (Molarity)
(iii) w/V (mass by volume percentage) (vii) m (Molality)
(iv) ppm. (parts per million)

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

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

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.

Give an example of a material used for making semipermeable membrane for
carrying out reverse osmosis.

What is “semi permeable membrane”?

How does sprinkling of salt help in clearing the snow covered roads in hilly
areas? Explain the phenomenon involved in the process.

Why is the vapour pressure of an aqueous solution of glucose lower than that
of water?

(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?

Why are aquatic species more comfortable in cold water in comparison to
warm water?

What is the significance of Henry’s Law constant KH?

Concentration terms such as mass percentage, ppm, mole fraction and molality
are independent of temperature, however molarity is a function of temperature.
Explain.

Explain the solubility rule “like dissolves like” in terms of intermolecular forces
that exist in solutions.

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.

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.

What do you mean by Henry’s Law? The Henry’s Law constant for oxygen dissolved in water is

4.34×104  atm at 25o C. If the partial pressure of oxygen in air is 0.2 atm, under atmospheric pressure conditions. Calculate the concentration in moles per Litre of dissolved oxygen in water in equilibrium with water air at 25o C.

What is Vant Hoff factor?

What is the Vant Hoff factor in K4[Fe(CN)6] and BaCl2 ? 

Why the molecular mass becomes abnormal?

Define molarity, how it is related with normality ?

How molarity is related with percentage and density of solution ? 

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

What is Vant Hoff factor , how is it related with

a. degree of dissociation      b. degree of association

Why NaCl is used to clear snow from roads ? 

why the boiling point of solution is higher than oure liquid

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.

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

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 x 10⁷ mm and 6.51 x 10⁷mm respectively, calculate the composition of these gases in water.

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.

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 ptotal' pchloroform' and pacetoneas a function of xacetone. The experimental data observed for different compositions of mixture is.

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.

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

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.

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.

Calculate the depression in the freezing point of water when 10 g ofCH₃CH₂CHClCOOH is added to 250 g of water. K_a = 1.4 x 10^-3, K_f = 1.86

K kg mol^-1.

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.

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

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 x 10^-3m aqueous solution required for the above dose.

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

If the solubility product of CuS is 6 x 10^-16, calculate the maximum molarity of CuS in aqueous solution.

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.

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.

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

Suggest the most important type of intermolecular attractive interaction in the following pairs.

(i) n-hexane and n-octane

(ii) I₂ and CCl₄

(iii) NaClO₄ and water

(iv) methanol and acetone

(v) acetonitrile (CH₃CN) and acetone (C₃H₆O).

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?

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.

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.

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.  i.            molar mass of the solute
2. ii.            vapour pressure of water at 298 K.

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%.

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.

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?

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?

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

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

State Henry's law and mention some important applications?

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

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

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.

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?

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.

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?

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?

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?

Define the following terms:

(i) Mole fraction

(ii) Molality

(iii) Molarity

(iv) Mass percentage.

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

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

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.

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. K_f= 3.9 K kg mol^-1.

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.

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.

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.

Henry's law constant for CO₂in water is 1.67 x 10⁸Pa at 298 K. Calculate the quantity of CO₂in 500 mL of soda water when packed under 2.5 atm CO₂pressure at 298 K.

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.

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.

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 H₂SO₄diluted to 500 mL.

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 H₂SO₄diluted to 500 mL.

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

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