Solutions and Colligative Properties

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2 46 Objective MHT-CET Chemistry 2 Solutions and Colligative Properties 2.1 Introduction 2.2 Types of Solutions 2.3 Concentration of Solutions of Solids in Liquids 2.4 Solubility of Gases in Liquids 2.5 Solid Solutions 2.6 Colligative Properties 2.7 Lowering of Vapour Pressure 2.8 Boiling Point Elevation 2.9 Freezing Point Depression 2.10 Osmosis and Osmotic Pressure 2.11 Abnormal Molecular Masses 2.12 van't Hoff Factor 2.1 Introduction Two-third of the earth is covered with water, the most essential, vital component for life. Water in the sea is not in pure form. It contains sodium chloride, magnesium chloride, calcium salts and gases like oxygen, carbon dioxide in dissolved state. Thus, sea water is a solution. Solution consists of at least two components, a medium and dissolved phase. The physical properties of solution are mainly originated by intermolecular forces of attraction between the solvent molecules. These intermolecular forces of attraction are changed by the presence of dissolved substances. The physical properties include vapour pressure, boiling point, freezing point and osmotic pressure. Solutions Solutions are mixtures of two or more components. Depending on sizes of the components, the mixtures are classified into three types : A coarse mixture : It is formed when the sizes of the constituent components are relatively bigger, e.g.; mixture of salt and sugar. A colloidal dispersion : It is formed when the sizes of the particles dispersed in solvent are in the range of 10 7 cm to 10 4 cm. Colloidal particles carry positive or negative charge which stabilizes colloidal dispersion e.g.; ferric hydroxide sol, arsenic sulphide sol, etc. Colloidal solutions are heterogeneous and can be easily separated. A true solution : A true solution is formed when soluble substances are dissolved in the solvent. The sizes of the particles dissolved are very small of the order of 10 8 cm. True solutions are homogeneous and cannot be separated into components by simple mechanical methods. ff A true solution is defined as a homogeneous mixture of two or more substances, the composition of which is not fixed and may be varied within certain limits. ff A solution is formed by two components, solvent and one or more solutes. The component of the solution which constitutes larger part of the solution is called solvent and the other component that constitutes smaller part is called solute. Homogeneous solution : Solution is homogeneous if its composition is uniform throughout the body of the solution. Heterogeneous solution : Solution is heterogeneous when two or more phases are present in it. Solvation : The process of interaction of solvent molecules with solute particles to form aggregates. When water is a solvent, the process of solvation is called hydration or aquation. ff The extent to which solute dissolves in solvent to form homogeneous solution depends on nature of solute and solvent. ff The general rule is, like dissolves like i.e., polar

3 Solutions and Colligative Properties solutes are soluble in polar solvents, (e.g.; NaCl in water) while non-polar solutes are soluble in nonpolar solvents (e.g.; iodine in CCl 4 ). Water is called universal solvent, as it is polar and has very high dielectric constant, hence, dissolves most of the polar solutes. Solutions containing two, three or four components are called binary, ternary and quaternary solutions respectively. Solutions prepared in water are called aqueous solutions and solutions in other solvents are called non-aqueous solutions. As the solute particles are very small, the components of true solutions cannot be separated by simple physical methods like centrifugation, filtration, etc. 2.2 Types of Solutions Solvent Solute Examples Solid Solid Alloys like brass, bronze, copper in gold etc. Solid Liquid Amalgams of mercury with metals 47 Solid Gas Hydrogen gas in palladium metal, pumice stone Liquid Solid Iodine in CCl 4, benzoic acid in C 6 H 6, sugar in water Liquid Liquid Ethanol in water Liquid Gas Oxygen, carbon dioxide in water Gas Solid Iodine in air Gas Liquid Chloroform in nitrogen Gas Gas Air, mixtures of non-reacting gases 2.3 Concentration of Solutions of Solids in Liquids The concentration of a solution is defined as the amount of solute dissolved in a specific amount of solvent. Solutions containing relatively less amount of solute are called dilute solutions and if it contains relatively more amount of solute then the solution is called concentrated solution. Concentration of solutions may be expressed in different ways as discussed below : Name Symbol Formula Definition Percentage by mass Volume percentage Mass by volume percentage Strength Parts per million %(w/w) %(v/v) Mass of solute Total mass of solution 100 Amount of solute in grams present in 100 g of solution. Volume of solute Total volume of solution 100 Volume of solute in ml dissolved in 100 ml of the solution. % (w/v) Mass of solute Total volume of solution in ml 100 Amount of solute in grams dissolved in 100 ml of the solution. g/l (or g/dm 3 ) ppm Mass of solute in grams 3 Volume of solution in L (or dm ) Mass or volume of solute Total mass or volume of solution 106 Molarity M Moles of solute Volume of solution in L(or dm 3 ) Molality m Moles of solute Mass of solvent in kg Mole fraction x n xa A na + nb Amount of solute in grams present in one litre (or dm 3 ) of solution. Number of parts of solute present in million (10 6 ) parts of solution. Number of moles of solute dissolved in one litre (or one dm 3 ) of solution. Number of moles of solute dissolved in 1 kg of the solvent. Ratio of number of moles of one component to the total number of moles of all the components. Effect of temperature No effect Changes with change of temperature. Changes with change of temperature. Changes with change of temperature. No effect Changes with change of temperature. No effect No effect

4 48 Objective MHT-CET Chemistry Illustration : 1.23 g of sodium hydroxide (molar mass 40) are dissolved in water and the solution is made to 100 cm 3. Calculate the molarity of the solution. Soln.: Amount of NaOH 1.23 g Volume of solution 100 cm 3 Mass of NaOH Moles of NaOH Molar mass of NaOH Moles of NaOH Molarity 1000 Volume of solution M 100 Illustration : 1.8 g of glucose (molar mass 180) are dissolved in 60 g of water. Calculate (a) the molality (b) mole fraction of glucose and water. Soln.: (a) Molality of solution Moles of solute Mass of solvent in g 1000 Moles of glucose \ Molality 1000 Mass of water m (b) Mole fraction Moles of solute Moles of solute + Moles of solvent 18. Moles of glucose 001. ; Moles of water Mole fraction of glucose ; Mole fraction of water Illustration : 4 g of sodium chloride was dissolved in 300 g of water. Calculate percentage by mass of sodium chloride in solution. Soln.: Percentage by mass of sodium chloride (w/w) mass of sodium chloride mass of sodium chloride + mass of water g %by mass 4 g+ 300g 304 Depending upon the quantity of solute dissolved in a liquid solvent, solutions can be of three types : f f Saturated solution : A solution which cannot dissolve any further amount of solute at a given temperature is called saturated solution. f f Unsaturated solution : A solution in which more amount of the solute can be dissolved at a given temperature is called unsaturated solution. f f Supersaturated solution : A solution in which amount of solute is more than it can dissolve at a particular temperature is called supersaturated solution. Solubility of a substance is its maximum amount that can be dissolved in a specified amount of solvent at a specified temperature. Factors affecting solubility of a solid in a liquid : f f Effect of temperature : If the dissolution process is endothermic (D sol H > 0), the solubility increases with rise in temperature. If dissolution process is exothermic (D sol H < 0) the solubility decreases with rise in temperature. f f Effect of pressure : Pressure does not have any significant effect on solubility of solids in liquids as these are highly incompressible. 2.4 Solubility of Gases in Liquids Gases are soluble in liquids including water. The solubility of gases like O 2, N 2, etc. are much low. O 2 molecules being non-polar, have less solubility in polar solvent, water. CO 2 and NH 3 gases are more soluble in water as CO 2 reacts with water to form carbonic acid and NH 3 reacts with water to form ammonium hydroxide. HCl gas is polar, its solubility is very high in water, forming hydrochloric acid. Factors affecting solubility of a gas in a liquid : f f Effect of pressure : The solubility of gas increases with the increase in external pressure. Henry s law - It states that the solubility of a gas in a liquid at constant temperature is proportional to the pressure of the gas above the solution. S P i.e., S K P where S is the solubility of the gas in mol dm 3, P is the pressure of the gas in atm, K is constant of proportionality and has the unit of mol dm 3 atm 1. If P 1 atm, then S K. Hence, Henry s constant K is defined as solubility of gas in mol dm 3 at 1 atmospheric pressure at reference temperature. If several gases are present then the solubility of any gas may be evaluated by using P as partial pressure of that gas in the mixture. ff Effect of temperature : According to Charles law, volume of a given mass of a gas increases with increase of temperature. Therefore, volume

5 Solutions and Colligative Properties of a given mass of dissolved gas in solution also increases with increase of temperature, so that it becomes impossible for the solvent in solution to accommodate gaseous solute in it and gas bubbles out. Hence, solubility of gas in liquid decreases with increase of temperature. f f Effect of addition of soluble salt : Solubility of dissolved gas is suppressed when a soluble salt is added to the solution of gas. Illustration : The solubility of nitrogen gas at 1 atm pressure at 25 C is mol dm 3. Calculate the solubility of N 2 gas from atmosphere at 25 C if atmospheric pressure is 1 atmosphere and partial pressure of N 2 gas at this temperature and pressure is 0.78 atm. Soln.: (i) S mol dm 3, P 1 atm N2 S K P N mol dm 3 K 1 atm K mol dm 3 atm 1 (ii) P 0.78 atm, S? S mol dm 3 atm atm mol dm 3 i.e. Solubility of N 2 is reduced to mol dm Solid Solutions A solid solution of two or more metals or of a metal or metals with one or more non-metals is called an alloy or solid solution. All the properties of the pure metals are improved when they form solid solutions, i.e., alloys. Duralumin (Al + Cu + Mg + Mn) : Light and strong as steel. Used in the construction of aircrafts. Aluminium bronze (Al + Cu + Mn) Lead alloy (Pb % Sb) : Acid resistant. Used for bearings, bullets, shrapnel and for manufacturing lead storage battery plates. Babbitt metal (Sb + Sn + Cu) : Antifriction alloy. Used in machine bearings. Stainless steel (Steel + Cr + Ni) : Resistant to corrosion. Used in cutlery. 49 Spiegeleisen (5-20% Mn in Iron ) and Ferromanganeous (70-80% Mn % Fe) : Used for making very hard steels and to manufacture rails, safes and heavy machinery. Manganin (84% Cu + 12% Mn + 4% Ni) : Has almost zero temperature coefficient of electrical resistance. Used for making electrical measurements. Amalgams (Hg + metals) : Used for extracting metals from ores. 2.6 Colligative Properties These are the properties that depend on the number of solute particles in solution and not on the nature of the solute particles. These are : Lowering of vapour pressure, Elevation of boiling point of solvent in solution, Depression of freezing point of solvent in solution and Osmotic pressure. 2.7 Lowering of Vapour Pressure Vapour pressure of liquids : ff The vapour pressure of a substance is defined as the pressure exerted by the gaseous state of that substance when it is in equilibrium with the solid or liquid phase. ff Vapour pressure of a liquid, increases with the increase of temperature. ff The boiling point of a liquid is a temperature at which vapour pressure of liquid becomes equal to external pressure. If the boiling is carried out in an open atmosphere then external pressure is the atmospheric pressure. Vapour pressure lowering : ff The vapour pressure of a liquid solvent is lowered when a non-volatile solute is dissolved in it to form a solution. ff This is due to the fact that in case of pure solvent, its surface area is completely occupied by volatile solvent molecules. While in case of solution of nonvolatile solute, its surface area is not completely available for volatile solvent; partly it is occupied by non-volatile solute. ff Hence, rate of evaporation of the solution will be less as compared to that of pure solvent and vapour pressure of solution is lower than that of the pure solvent. ff If p 1 is the vapour pressure of pure solvent and p is the vapour pressure of the solution of non-volatile

6 50 Objective MHT-CET Chemistry ff ff solute in the same solvent, then p < p 1 and the lowering of vapour pressure is, Dp p 1 p The difference between vapour pressure of pure solvent and the vapour pressure of solvent from solution is called vapour pressure lowering. The ratio of vapour pressure lowering of solvent from solution to the vapour pressure of pure solvent is called the relative lowering of vapour pressure. Dp p p p p 1 Raoult s law 1 1 The law states that, the partial vapour pressure of any volatile component of a solution is the product of vapour pressure of that pure component and the mole fraction of the component in the solution. p 1 p 1 x 1 and p 2 p 2 x 2 where p 1 and p 2 are vapour pressures of pure components 1 and 2 respectively, at the same temperature. Total vapour pressure, p total of solutions of two volatile components is the sum of partial vapour pressures of the two components, p total p 1 + p 2 x 1 p 1 + x 2 p 2 (x 1 )p 1 + (1 x 1 ) p 2 p 2 + (p 1 p 2 )x 1 The solution which obeys Raoult s law over the entire range of concentration is called an ideal solution. If a solution does not obey Raoult s law, the solution is nonideal. If y 1 and y 2 are the mole fractions of the components 1 and 2 respectively in the vapour phase then, p 1 y 1 p total and p 2 y 2 p total Raoult s law for a solution of non-volatile solute Non-volatile solute does not evaporate and does not contribute to the total vapour pressure of solution. The vapour pressure of pure component A 1 is p 1 and that of component A 2 is p 2 0. p p 2 + (p 1 p 2 )x 1 (as p 2 0) p 0 + (p 1 0)x 1 i.e., p p 1 x 1 (1) The lowering of vapour pressure Dp is given by, Dp p 1 p p 1 p 1 x 1 p 1 (1 x 1 ) But 1 x 1 x 2 Hence, Dp p 1 x 2 (2) Lowering of vapour pressure is the product of vapour pressure of pure solvent and mole fraction of nonvolatile solute dissolved in volatile solvent to form a solution. Thus the lowering of vapour pressure depends on nature of pure solvent and concentration of solute in mole fraction. Now the relative lowering of vapour pressure is given by, Dp p 1 p px 1 2 x2 p 1 p 1 p 1 Hence, relative lowering of vapour pressure x 2 Equation (2) proves that the lowering of vapour pressure is a colligative property because it depends on the concentration of non-volatile solute. Molar mass of solute and relative lowering of vapour pressure Dp p 1 p n2 W2 / M 2 x2 p p n n W M W M / 1+ 2 / 2 For dilute solutions n 1 >> n 2 \ Dp n p 2 W M WM n 2 / W M WM 1 1 1/ Knowing the masses of non-volatile solute and the solvent in dilute solutions and by determining experimentally vapour pressure of pure solvent and the solution it is possible to determine molar mass of a non-volatile solute. Illustration : Calculate the weight of a non-volatile solute (mol. wt. 40), which should be dissolved in 114 g octane to reduce its vapour pressure to 80%. Soln.: Given: p (80/100)p, M 2 40 W g, M We know, p p W2 M1 p M2 W1 p ( / ) p W \ p \ W 2 18 g (weight of solute required) 2.8 Boiling Point Elevation Boiling point is defined as the temperature at which the vapour pressure of liquid becomes equal to the atmospheric pressure. ff It is a characteristic property of liquids and is a criterion to check the purity of liquid. ff It increases with increase in external pressure. ff Liquids having greater intermolecular forces have high boiling points.

7 Solutions and Colligative Properties Elevation of boiling point : ff ff Solution has lower vapour pressure and hence higher boiling point than pure solvent. The increase in the boiling point, DT b T b T b is known as elevation of boiling point. For dilute solutions, DT b m or DT b K b m K W B 1000 b MB WA 1000 W K or M B b B DTb WA where m is molality of solution and K b is called boiling point elevation constant or molal elevation constant or ebullioscopic constant, having unit K kg mol 1. Illustration : The molal elevation constant for water is 0.51 K kg mol 1. Calculate the b. pt. of solution made by dissolving 6 g urea in 200 g water. Soln.: Given: W 2 6 g, M 2 60 (urea), W g, K b 0.51 K kg mol 1 We know, DT b 1000 Kb W2 M2 W Substituting values, DT b C As elevation in b. pt C \ B. pt. of solution C 2.9 Freezing Point Depression Freezing point of a liquid is the temperature at which the vapour pressure of solid is equal to the vapour pressure of liquid. Depression of freezing point : The lowering of vapour pressure of a solution causes a lowering of the freezing point compared to that of the pure solvent. The decrease in freezing point, DT f T f T f is known as depression in freezing point. Freezing point depression and vapour pressure lowering : For dilute solutions, DT f p 1 p DT f m or DT f K f m where K f is known as freezing point depression constant or molal depression constant or cryoscopic constant, having unit K kg mol Depression in freezing point and molar mass of the solute : DT f K W B 1000 f M W or M K f W B 1000 B B A DTf WA Illustration : The freezing point of a solution containing 50 cm 3 of ethylene glycol in 50 g water is found to be 34 C. Assuming ideal behaviour, calculate the density of ethylene glycol. (K f for H 2 O 1.86 K kg mol 1 ) Soln.: Given: V ethylene glycol 50 cm 3, W 1 50 g K 1.86 K kg f(h2 O) mol 1, M 2 62 (glycol) DT f 34 C, W 2 50 d (glycol) We know, DT f 1000 Kf W2 M2 W ( 50 d) Substituting values, \ d g/cm Osmosis and Osmotic Pressure Osmosis : The net spontaneous flow of the solvent molecules from the solvent to the solution or from a less concentrated solution to a more concentrated solution through a semipermeable membrane. Osmotic pressure : The minimum excess pressure that has to be applied on the solution to prevent the entry of the solvent into the solution through the semipermeable membrane. ff Two or more solutions having same osmotic pressure at a given temperature are called isotonic solutions. ff If one solution is of lower osmotic pressure, it is called hypotonic with respect to the more concentrated solution. The more concentrated solution is said to be hypertonic with respect to the dilute solution. ff If a pressure higher than the osmotic pressure is applied on the solution, the solvent will flow from the solution into the pure solvent through the semipermeable membrane and the process is called reverse osmosis. It is used in desalination of sea water. Laws of osmotic pressure van t Hoff Boyle s law : It states that, at constant temperature the osmotic pressure (p) of a dilute solution is directly proportional to its molar concentration or inversely proportional to the volume of the solution. At constant T, p C (in mol L 1 )

8 52 Objective MHT-CET Chemistry If n moles of solute is dissolved in V litres then, C n V n 1 \ p or p for constant n V V \ pv constant or p C constant van t Hoff-Charles law : It states that, the concentration remaining constant, the osmotic pressure of a dilute solution is directly proportional to the absolute temperature. At constant C, p T i.e., p T constant van t Hoff general solution equation : p CRT R J K 1 mol 1 if p is in N m 2 and V in m 3 R L atm K 1 mol 1 if p is in atm and V in dm 3 Determination of molar mass from osmotic pressure : p n 2 V RT, p W 2 RT, M 2 W 2 RT M2 V p V van t Hoff Avogadro s law : It states that, two solutions of equal concentrations of different solutes exert same osmotic pressure at the same temperature. It can also be, stated as, equal volumes of isotonic solutions contain an equal number of solute particles at the given temperature. For a given solution pv nrt p 1 V 1 n 1 RT 1 for solution 1 (i) p 2 V 2 n 2 RT 2 for solution 2 (ii) If p 1 p 2, T 1 T 2 and V 1 V 2 then from equations (i) and (ii), n 1 n 2 Since, number of moles are equal, number of molecules are also equal. Hence, osmotic pressure and temperature remaining the same, equal volumes of solutions would contain equal number of moles of the solute. For isotonic solutions of equal volume, n 1 n Abnormal Molecular Masses For substances undergoing association or dissociation in solution, the molecular mass determined by studying any of the colligative properties is different than the theoretically expected value, and the substance is said to show abnormal molecular mass. Dissociation of electrolyte solutes : Electrolytic solutes when dissolved in solvent dissociate to produce multiple number of ions/particles. This results in increase of number of solute particles in solution which in turn results in increase of colligative properties and increase of DT f /m value and the value of DT f /m is approximately equal to integral multiple of K f value. The value of integral is equal to total number of ions produced on dissociation as shown : (i) HCl H + + Cl ; 2 particles; DT f /m K mol 1 kg + (ii) NH 4 Cl NH 4 + Cl ; 2 particles; DT f /m K mol 1 kg (iii) CoCl 2 Co Cl ; 3 particles; DT f /m K mol 1 kg (iv) K 2 SO 4 2K + + SO 2 4 ; 3 particles; DT f /m K mol 1 kg (v) AlCl 3 Al Cl ; 4 particles; DT f /m K mol 1 kg DT f /m K f value observed in case of solutions of electrolytes may not be exactly two fold, three fold etc of theoretical K f value observed in case of solutions of non-electrolyte solute. The value fluctuates with degree of dissociation of solute in solution. Association of solutes : In some non-polar solvents, two or more molecules of solute associate to form bigger molecules. For example, in benzene solutes like acetic acid, benzoic acid, etc. associate to form dimers. This association is due to the hydrogen bonding between these molecules. 2CH 3 COOH (CH 3 COOH) 2 2C 6 H 5 COOH (C 6 H 5 COOH) 2 Hence, numbers of solute particles are reduced to almost half. Observed molecular masses of these species are almost twice the expected values in dilute solutions. Due to association the total number of molecules in solution will be almost half of the number of molecules of the substance dissolved. Hence such solutions show abnormally low colligative properties. The observed molecular masses are almost double van t Hoff Factor The colligative properties of electrolytes may be expressed in relation to colligative properties of nonelectrolytes by using van t Hoff factor i. It is defined as the ratio of observed colligative property produced by a given concentration of electrolyte solution to the property observed for the same concentration of nonelectrolyte solution.

9 Solutions and Colligative Properties Observed value of the colligative property i Theoretical value of the colligative property or i Theoretical molecular mass Observed molecular mass Mth Mo Total number of moles of particles after association/ dissociation i, Number of moles of particles before association / dissociation for association, i < 1; for dissociation, i > 1 van t Hoff factor ( i) and degree of dissociation (a) : i a 1 n 1 ; M(theoretical) i [ 1+ ( n 1) a] M(observed) M(theoretical) M(observed) a M(observed) ( n 1) van t Hoff factor ( i) and degree of association (a) : 1 i a 1 1/n Modified equations for colligative properties : p1 p1 i n 2, DT b ik b m, DT f ik f m, p i n 2 RT/V p1 n1 53 Illustration : A decimolar solution of potassium ferrocyanide is 50% dissociated at 300 K. Calculate the osmotic pressure of the solution (R JK 1 mol 1 ). Soln.: Initial number of moles of K 4 [Fe(CN) 6 ] 0.1, (as the solution is decimolar). a degree of dissociation 50% 1/2 Thus, we may represent the facts as below : K 4 [Fe(CN) 6 ] 4K + + [Fe(CN) 6 ] 4 total Initial no of moles After 0.1(1 a) 0.1 (4a) 0.1 (a) 0.1(1 + 4a) dissociation 0.1 [1 + (4 1/2)] 0.3 van t Hoff factor, Number of particles after dissociation i Actual number of particles before dissociation pv inrt p inrt V icrt (C n/v molarity 0.1 mol L 1 ) or 01. mol 10 3 m mol m 3 or, p Nm atm

10 54 Objective MHT-CET Chemistry Mass Percentage : ( ww / )% of solution Mass of solute Total mass ofsolution 100 Volume Percentage : (/ vv )% of solution Volume of solute Total volume ofsolution 100 Mass by volume percentage : ( WV / )% of solution Mass of solute Total volume ofsolution inml 100 Moles Moles SOLUTIONS AND COLLIGATIVE PROPERTIES within Henry s Law : It states that the solubility of a gas in a liquid at constant temperature is proportional to the pressure of the gas above the solution. S P i.e., S K P i p A p A x A p B p B x B Isotonic Solutions : Solutions having same osmotic pressure. Hypotonic Solutions : Solutions having lower osmotic pressure than the other. Hypertonic Solutions : Solutions having higher osmotic pressure than the other. Laws of Osmotic Pressure: van t Hoff-Boyle s law : At constant T, V constant or 1 constant C ( in moll ) van t Hoff-Charles law : At constant C, constant van t Hoff generalsolutionequation : CRT van t Hoff-Avogadro s law : For isotonic solutions of equal volume, n1 n2. Strength T Mass of solute in grams 3 Volume of solution inl(or dm ) van t Hoff factor : i Observed valueof colligativeproperty Theoretical valueof colligativeproperty Theoretical valueofmolecularmass Observed valueofmolecularmass Degree of Dissociation andassociation : 1 (dissociation) i n 1 1 (association) i 1 1/ Modified Equations of Colligative Properties : p p in p n Tb ikm b Tf ikm f in RT / V 2 n x x K K K K Osmosis : The spontaneous and unidirectional flow of solvent molecules through a semipermeable membrane, into the solution or flow of solvent from a solution of lower concentration to the solution of higher concentration through a semipermeable membrane is called osmosis. The excess of pressure on the side of solution that stops the net flow of solvent into solution through semipermeable membrane is called osmotic pressure.

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12 Solutions and Colligative Properties 55 Multiple Choice Questions LEVEL Introduction 1. The mixture of salt and sugar is called a (a) coarse mixture (b) homogeneous mixture (c) racemic mixture (d) solution mixture. 2. In a solution, the larger proportion of the component is known as (a) solution (b) solute (c) solvent (d) mixed solution. 3. A solution is defined as a (a) homogeneous mixture of two or more substances (b) heterogeneous mixture of two or more substances (c) homogeneous mixture of liquid and solid components only (d) homogeneous mixture consisting water as one of the components. 4. The substances involved in solution are called (a) mole (b) atoms (c) molecules (d) components. 5. The scientist who won the first Noble prize in chemistry in the year 1901, for his work in solutions was (a) van t Hoff (b) Beckmann (c) Raoult (d) Jean Nollet. 6. In solution, the molecular size of particles is of the order of (a) 10 8 cm (b) 10 9 m (c) > 10 9 m (d) 10 9 cm 7. The new method to determine alcohol content of a wine was discovered in 1870 by (a) Newton (b) Joule (c) Raoult (d) C.A. Wurtz. 8. A solution having three components is called a (a) quaternary solution (b) binary solution (c) single solution (d) ternary solution. 2.2 Types of Solutions 9. An example of a solution having liquid in gas is (a) moist air (b) dry air (c) Au-Hg (d) C 2 H 5 OH + H 2 O 10. Which of the following is not a solution? (a) Air (b) A gold ring (c) Smoke (d) Salt solution 11. Solutions are of types. (a) three (b) six (c) nine (d) eleven 12. Which of the following possesses physical states of solute and solvent as liquid and solid respectively? (a) Solution of sugar in water (b) Zinc amalgam (c) Solution of naphthalene in benzene (d) Brass 13. Which of the following pairs of solutions having different physical states of solute? (a) Homogeneous mixture of chloroform in N 2 gas, solution of CO 2 in water (b) Brass, homogeneous mixture of camphor in N 2 gas (c) Sodium amalgam, moist air (d) Solution of H 2 gas in Pd metal, mixture of N 2 and O In vaporization of liquids into air, liquid dissolves into air hence liquid is (a) solution (b) solute (c) solvent (d) mixture. 15. Sugar dissolved in water is a type of (a) solid in solid solution (b) solid in gas solution (c) solid in liquid solution (d) gas in solid solution. 2.3 Concentration of Solutions of Solids in Liquids 16. Dissolution of calcium chloride in water is exothermic process while that of ammonium nitrate is endothermic process, the observation is

13 56 Objective MHT-CET Chemistry (a) (b) (c) (d) solubility of calcium chloride decreases with increase in temperature and that of ammonium nitrate increases with increase in temperature solubilities of both decrease with increase in temperature solubilities of both increase with increase in temperature solubility of calcium chloride increases with increase in temperature and that of ammonium nitrate decreases with increase in temperature cm 3 of C 2 H 5 OH on dissolving in 200 cm 3 of water forms 220 cm 3 solution of C 2 H 5 OH. What would be the percentage by volume of C 2 H 5 OH in the solution? (a) 22% (b) 11% (c) 01% (d) 10% 18. The volume of 2 M NaOH solution is 0.1 dm 3. What will be the volume of decimolar NaOH in dm 3? (a) 0.1 (b) 0.2 (c) 1.5 (d) A molal solution is one that contains one mole of a solute in (a) 1000 g of the solvent (b) one litre of the solvent (c) one litre of the solution (d) 1000 g of the solution. 20. When 10 g of caustic soda is dissolved in 250 cm 3 of water, molarity of the solution is (a) 1 M (b) 0.5 M (c) 0.25 M (d) 0.1 M 21. A solution contains 0.5 mole of a solute in 400 g of water, its molality would be (a) 1.25 m (b) m (c) 2.51 m (d) m 22. One part of solute in one million parts of solvent is expressed as (a) ppm (b) milligrams/100 cc (c) grams/litre (d) grams/100 cc g of glucose (molar mass 180 g/mol) is present in 500 g of water, the molarity of the solution is (a) 0.2 M (b) 0.4 M (c) 0.8 M (d) 1.0 M 24. The molality of 648 g of pure water is (a) 36 m (b) 55.5 m (c) 3.6 m (d) 5.55 m 25. An aqueous solution contains 25% ethanol and 50% acetic acid by mass. Calculate the mole fraction of acetic acid in this solution. (a) (b) (c) (d) When 0.5 g of solute is present in 10 7 g of a solution, the ppm of solute will be (a) 0.5 (b) 0.05 (c) 10 6 (d) g of urea was dissolved in 500 g of water. The percentage (by mass) of urea in the solution is (a) 0.86% (b) 1.186% (c) 11.86% (d) 0.08% cm 3 of ethyl alcohol was dissolved in 400 cm 3 of water to form 454 cm 3 of solution of ethyl alcohol. The percentage by volume of ethyl alcohol in water is (a) 0.12.% (b) 1.2% (c) 12.78% (d) 0.01% g of ethyl alcohol (molar mass 46 g mol 1 ) is dissolved in 54 g of water (molar mass 18 g mol 1 ). The mole fraction of ethyl alcohol and water in solution are respectively (a) 0.7 and 0.3 (b) and (c) and (d) and % (w/w) solution of ethylene glycol in water, an antifreezer is used in cars as coolant. It lowers freezing point of water to 17.6 C. The mole fraction of ethylene glycol is (a) (b) (c) (d) A solution of NaOH (molar mass 40 g mol 1 ) was prepared by dissolving 1.6 g of NaOH in 500 cm 3 of water. The molarity of solution is (a) 0.2 mol dm 3 (b) 0.02 mol dm 3 (c) 0.08 mol dm 3 (d) 0.8 mol dm g of urea was dissolved in 100 g of water. The molality of solution is (N 14, H 1, C 12, O 16) (a) mol kg 1 (b) mol kg 1 (c) mol g 1 (d) mol g g of sugar was dissolved in water to produce g of sugar syrup. The molality and mole fraction of sugar in the syrup are respectively (C 12, H 1, O 16) (a) m, (b) 0.05 m, 0.02 (c) m, (d) 0.05 m, The molarity and molality of sulphuric acid solution of density g cm 3 containing 27% by mass of sulphuric acid (molar mass of H 2 SO 4 98 g mol 1 ) are respectively

14 Solutions and Colligative Properties (a) M, 3.77 m (b) 0.03 M, 0.3 m (c) 0.33 M, 7.3 m (d) 33.1 M, 0.7 m 35. Commercially available concentrated hydrochloric acid is an aqueous solution containing 38% HCl gas by mass. If its density is 1.1 g cm 3, the molarity and mole fraction of HCl solution are respectively (a) 1.14 M and (b) M and (c) M and (d) M and A sample of drinking water was found to be severely contaminated with chloroform which is supposed to be carcinogen. If the level of contamination was 15 ppm (by mass) then the molality of chloroform in the water sample is (a) m (b) m (c) m (d) m g of glucose is dissolved in 400 g of water. What is the percentage by mass of glucose solution? (a) 78.7% (b) 7.87% (c) 87.7% (d) 77% 38. A solution is prepared by dissolving certain amount of solute in 500 g of water. If the percentage by mass of a solute in solution is 2.38 then the mass of solute will be (a) g (b) g (c) g (d) 1219 g cm 3 of methyl alcohol is dissolved in 25.2 g of water. The % by mass of methyl alcohol and mole fraction of methyl alcohol are respectively (Given density of methyl alcohol g cm 3 and C 12, H 1, O 16) (a) 1.26% and (b) 12.68% and (c) 12% and (d) 1.26% and cm 3 of benzene is dissolved in 16.8 cm 3 of xylene. What is the % by volume of benzene? (a) 24.43% (b) 4.324% (c) 43.24% (d) 0.43% 41. What is the mole fraction of HCl in aqueous solution of HCl containing 24.8% of HCl by mass? (H 1, Cl 35.5) (a) (b) (c) (d) What is the mole fraction of solute in its 2 molal aqueous solution? (a) (b) 3.47 (c) (d) The molality and molarity of HNO 3 in a solution containing 12.2% HNO 3 are respectively (Given density of HNO g cm 3, H 1, N 14, O 16) (a) 2.01 m and M (b) 1.2 m and 2.6 M (c) m and 2.01 M (d) 20.6 m and 20 M Sulphuric acid is 95.8% by mass. What is the mole fraction and molarity of H 2 SO 4 solution having density 1.91 g cm 3? (H 1, S 32, O 16) (a) and M (b) and M (c) 0.07 and 7.86 M (d) and M 45. Aqueous solution of NaOH is marked 10% (w/w). The density of the solution is g cm 3. The molarity and molality of solution are respectively (Na 23, H 1, O 16) (a) M and 2.77 m (b) 0.27 M and 0.26 m (c) 0.26 M and 0.02 m (d) 20.7 M and 20.6 m 46. Battery acid is 4.22 M aqueous H 2 SO 4 solution, and has density of 1.21 g cm 3. What is the molality of H 2 SO 4? (H 1, S 32, O 16) (a) mol/g (b) mol/kg (c) mol/kg (d) mol/kg 47. A molal solution is one that contains one mole of solute in (a) one litre of the solvent (b) 1000 g of the solvent (c) one litre of the solution (d) 22.4 litres of solution. 48. Which of the following is independent of temperature? (a) Molarity (b) Molality (c) Both (a) and (b) (d) None of these g of NaOH (molar mass 40 g mol 1 ) is dissolved in 500 cm 3 of water. Molality of resulting solution is (a) 0.1 m (b) 0.5 m (c) 1.5 m (d) 1.0 m 50. Molarity of solution depends on (a) temperature (b) nature of solute dissolved (c) mass of solvent (d) pressure. 51. Density of water is 1 g/ml. The concentration of water in mol/litre is (a) 1000 (b) 18 (c) (d) The solutions A and B are 0.1 M and 0.2 M in a substance. If 100 ml of A is mixed with 25 ml of B and there is no change in volume, the final molarity of the solution is (a) 0.15 M (b) 0.18 M (c) 0.30 M (d) 0.12 M

15 58 Objective MHT-CET Chemistry 53. The molarity of a solution that contains 49 g H 3 PO 4 in 2.0 L of a solution is (a) 0.25 M (b) 0.50 M (c) 0.75 M (d) 1.0 M 54. The molarity of the solution containing 7.1 g of Na 2 SO 4 in 100 ml of aqueous solution is (a) 1 M (b) 2 M (c) 0.05 M (d) 0.5 M 55. If 60 cm 3 of ethyl alcohol is dissolved in 300 cm 3 of water then the percentage by volume of ethyl alcohol is (a) 16.66% (b) 15.76% (c) 17.86% (d) 18.96% 56. What volume of 0.8 M solution contains 0.1 mol of the solute? (a) 62.5 ml (b) 100 ml (c) 500 ml (d) 125 ml ml of 3.0 M HNO 3 are mixed with 75 ml of 4.0 M HNO 3. If the volumes are additive, the molarity of the final mixture would be (a) 3.25 M (b) 4.0 M (c) 3.75 M (d) 3.50 M 58. The amount of anhydrous Na 2 CO 3 present in 250 ml of 0.25 M solution is (a) g (b) g (c) 6.0 g (d) g ml of HCl solution requires ml of 0.01 M NaOH solution for complete neutralization. The molarity of HCl solution is (a) M (b) M (c) 0.99 M (d) 9.9 M 60. If 5.85 g of NaCl (molecular weight 58.5 g mol 1 ) is dissolved in water and the solution is made up to 0.5 litre, the molarity of the solution will be (a) 0.2 M (b) 0.4 M (c) 1.0 M (d) 0.1 M 61. If 1 M and 2.5 litre NaOH solution is mixed with another 0.5 M and 3 litre NaOH solution, then molarity of the resultant solution will be (a) 1.0 M (b) 0.73 M (c) 0.80 M (d) 0.50 M 62. To prepare a solution of concentration of 0.03 g/ml of AgNO 3, what amount of AgNO 3 should be added in 60 ml of solution? (a) 1.8 g (b) 0.8 g (c) 0.18 g (d) g 63. A solution of CaCl 2 is 0.5 mol/litre, then the moles of chloride ions in 500 ml will be (a) 0.25 (b) 0.50 (c) 0.75 (d) The sum of mole fractions of A, B and C in an aqueous solution containing 0.2 moles of each A, B and C is (a) 0.6 (b) 0.2 (c) 1.0 (d) Solubility of Gases in Liquids 65. According to Henry's law (a) S KP (b) S K/P (c) S P/K (d) S KP 66. If Henry's law constant for oxygen is mol dm 3 atm 1 and its partial pressure is 0.20 atm, the concentration of dissolved oxygen at NTP will be (a) mol dm 3 (b) mol dm 3 (c) mol dm 3 (d) mol dm The unit of Henry's constant is (a) mol dm 3 atm 1 (b) mol dm 3 atm (c) mol 1 dm 3 atm (d) mol 1 dm 3 atm What is the concentration of dissolved oxygen at 25 C at 1 atmospheric pressure if partial pressure of oxygen is 0.22 atm? The Henry s law constant for oxygen is mol dm 3 atm 1. (a) mol dm 3 (b) mol dm 3 (c) mol dm 3 (d) mol dm What is the Henry s law constant of dissolved O 2 at 10 C at 1 atmospheric pressure, if partial pressure of oxygen is 0.24 atm? The concentration of dissolved oxygen is mol dm 3. (a) mol dm 3 atm 1 (b) mol dm 3 atm 1 (c) mol dm 3 atm 1 (d) data insufficient. 70. Solubility of a gas in a liquid increases with (a) increase of pressure and increase of temperature (b) decrease of pressure and increase of temperature (c) increase of pressure and decrease of temperature (d) decrease of pressure and decrease of temperature. 71. Which law states that the amount of gas dissolved in a given mass of solvent at any temperature is directly proportional to pressure of the gas above the solution? (a) Raoult s law (b) Boyle s law (c) Charles law (d) Henry s law

16 Solutions and Colligative Properties 2.5 Solid Solutions 72. Lead is hardened by the addition of (a) 10-20% aluminium (b) 5-20% manganese (c) 10-20% antimony (d) 20-30% iron 73. Babbitt metal is an alloy of (a) bismuth with tin and copper (b) antimony with tin and copper (c) lead with arsenic (d) aluminium with copper and manganese. 74. Amalgam is (a) a solution of gas in gas (b) a solution of liquid in gas (c) a solution of metals in liquid metal (d) a solution of solid in gas. 75. Stainless steel contains (a) chromium (b) nickel (c) both (a) and (b) (d) none of these. 76. An alloys containing zero temperature coefficient of electrical resistance is (a) manganin (b) duralumin (c) bronze (d) spiegeleisen. 77. An alloy is (a) a solution of solid in liquid (b) a solution of solid in gas (c) a solution of solid in plasma (d) a solution of solid in solid to 20% manganese in iron is (a) ferromanganeous (b) manganin (c) duralumin (d) spiegeleisen. 79. An alloy manganin contains (a) 84% Cu, 12% Mn and 4% Ni (b) 70-80% Mn, 30-20% Fe (c) 10-20% Sb, 90-80% Pb (d) Al, Cu, Mg, and Mn. 2.6 Colligative Properties 80. Which of the following is not a colligative property? (a) Osmotic pressure (b) Elevation in boiling point (c) Vapour pressure (d) Depression in freezing point 81. Which of the following is a colligative property? (a) Osmotic pressure (b) Boiling point (c) Vapour pressure (d) Freezing point 82. Colligative properties are applicable to (a) ideal dilute solutions (b) non-ideal concentrated solutions (c) non-ideal solutions (d) ideal concentrated solutions. 83. The colligative properties of a solutions depend on (a) nature of solute particles present in it (b) nature of solvent used (c) number of solute particles present in it (d) number of moles of solvent only. 84. Which of the following is not the colligative property? (a) DT f (b) DT b (c) K b (d) Osmotic pressure Colligative properties are used for the determination of (a) molar mass (b) equivalent weight (c) arrangement of molecules (d) melting point and boiling point. 86. Which of the following is a colligative property? (a) Conductance of a solution (b) Surface tension of a solution (c) Osmotic pressure of a solution (d) Radioactivity of a solution 87. Which is not a colligative property? (a) Refractive index (b) Lowering of vapour pressure (c) Depression of freezing point (d) Elevation of boiling point 2.7 Lowering of Vapour Pressure 88. Which of the following is incorrect? (a) Relative lowering of vapour pressure is independent of the nature of the solute and the solvent (b) Relative lowering in vapour pressure is a colligative property (c) Vapour pressure of a solution is lower than the vapour pressure of the solvent (d) Relative lowering of vapour pressure is directly proportional to the original pressure. 89. Which one of the following is not an expression for Raoult s law for a solution containing two volatile components A and B? p A and p B are the partial vapour pressures of A and B, p A and p B are the vapour pressures of pure A and B, x A and x B are mole fractions of A and B in solution.

17 60 Objective MHT-CET Chemistry (a) p A p A x A (b) P total p A x A + p B x B (c) Dp p B x B (d) Dp p A x A 90. Lowering of vapour pressure is a colligative property because, it depends on the concentration of (a) volatile solute (b) non-volatile solute (c) volatile solvent (d) non-volatile solvent. 91. At 25 C, the total pressure of an ideal solution obtained by mixing 3 moles of A and 2 moles of B, is 184 torr. What is the vapour pressure (in torr) of pure B at the same temperature? (vapour pressure of pure A, at 25 C, is 200 torr.) (a) 180 (b) 160 (c) 16 (d) The relative lowering of vapour pressure is equal to p 1 (a) (b) p p1 Dp p (c) Dp p1 p (d) p 1 Dp 93. The aqueous solution that has the highest value of relative lowering of vapour pressure at a given temperature is (a) 0.1 molal sodium phosphate (b) 0.1 molal barium chloride (c) 0.1 molal sodium chloride (d) 0.1 molal glucose. 94. For dilute solutions, Raoult s law states that (a) lowering of vapour pressure is equal to the mole fraction of the solute (b) relative lowering of vapour pressure is equal to the mole fraction of the solvent (c) relative lowering of vapour pressure of the solvent is equal to the mole fraction of the solute (d) vapour pressure of the solution is equal to the vapour pressure of the solvent. 95. Vapour pressure of dilute aqueous solution of glucose is 750 mm of mercury at 373 K. The mole fraction of solute is (a) 1/76 (b) 1/7.6 (c) 1/38 (d) 1/ Vapour pressure of a solution of 5 g of non-electrolyte in 100 g of water at a particular temperature is 2985 N/m 2. The vapour pressure of pure water is 3000 N/m 2, the molecular weight of the solute is (a) 90 g mol 1 (b) 200 g mol 1 (c) 180 g mol 1 (d) 380 g mol The vapour pressure of a solution containing kg of solute in 0.1 kg of water at 298 K is mm Hg. Given that the vapour pressure of water at 298 K is mm Hg. The molar mass of the solute will be (a) 69 g mol 1 (b) 95 g mol 1 (c) 60 g mol 1 (d) 90 g mol A solution is prepared from kg of an unknown substance and kg acetone at 313 K. The vapour pressure of pure acetone at this temperature is atm. The vapour pressure of solution is kg mol 1 if the molar mass of substance is (a) atm (b) atm (c) atm (d) atm 99. The vapour pressure of 2.1% solution of a nonelectrolyte in water at 100 C is 755 mm Hg. What is the molar mass of the solute? (a) kg/mol (b) g/mol (c) 5.86 kg/mol (d) g/mol 100. The vapour pressure of water at 20 C is 17 mm Hg. What is the vapour pressure of a solution containing 2.8 g of urea (NH 2 CONH 2 ) in 50 g of water? (N 14, C 12, H 1) (a) mm of Hg (b) mm of Hg (c) mm of Hg (d) mm of Hg 101. In an experiment, g of mannitol was dissolved in 100 g of water. The vapour pressure of water was lowered by mm Hg from mm Hg. The molar mass of mannitol is (a) g/mol (b) kg/mol (c) g/mol (d) g/mol 102. According to the Raoult s law, the relative lowering of vapour pressure is equal to the (a) mole fraction of solvent (b) mole fraction of solute (c) independent of mole fraction of solute (d) molality of solution Partial pressure of solvent in solution of non-volatile solute is given by equation, (a) p x 2 p 1 (b) p 1 xp (c) p x 1 p 1 (d) p 1 x 1 p 104. When partial pressure of solvent in solution of nonvolatile solute is plotted against its mole fraction, nature of graph is (a) a straight line passing through origin (b) a straight line parallel to mole fraction of solvent

18 Solutions and Colligative Properties (c) (d) a straight line parallel to vapour pressure of solvent a straight line intersecting vapour pressure axis Relative lowering of vapour pressure of solution is a (a) property of solute (b) property of solute as well as solvent (c) property of solvent (d) colligative property Vapour pressure of solution of a non-volatile solute is always (a) equal to the vapour pressure of pure solvent (b) higher than vapour pressure of pure solvent (c) lower than vapour pressure of pure solvent (d) constant The vapour pressure at equilibrium of a liquid in a closed vessel depends on (a) pressure (b) concentration (c) temperature (d) volume The vapour pressure of water at 300 K in a closed container is 0.4 atm. If the volume of the container is doubled, its vapour pressure at 300 K will be (a) 0.8 atm (b) 0.2 atm (c) 0.4 atm (d) 0.6 atm 109. At 300 K when a solute is added to a solvent its vapour pressure over the mercury reduces from 50 mm to 45 mm. The value of mole fraction of solute will be (a) (b) (c) (d) If p 1 and p are the vapour pressures of a solvent and its solution respectively, and if x 1 and x 2 are the mole fractions of the solvent and solute respectively then (a) p p 1 x 1 (b) p p 1 x 2 (c) p 1 p x 2 (d) p p 1 (x 1 /x 2 ) 111. The vapour pressure of pure liquid A is 0.80 atm. On mixing a non-volatile solute B to A, its vapour pressure becomes 0.6 atm. The mole fraction of B in the solution is (a) (b) 0.25 (c) 0.50 (d) The vapour pressure of two liquids P and Q are 80 and 60 torr respectively. The total vapour pressure of solution obtained by mixing 3 moles of P and 2 moles of Q would be (a) 140 torr (b) 20 torr (c) 68 torr (d) 72 torr g of urea (mol. wt. 60) was dissolved in 9.9 moles of water. If the vapour pressure of pure water is p 1, the vapour pressure of solution is (a) 0.10 p 1 (b) 1.10 p 1 (c) 0.90 p 1 (d) 0.99 p The vapour pressure of a solvent is decreased by 10 mm of mercury when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.2. What should be the mole fraction of the solvent, if the decrease in the vapour pressure is 20 mm of mercury? (a) 0.8 (b) 0.6 (c) 0.4 (d) The vapour pressure of a pure liquid A is 70 torr at 27 C. It forms an ideal solution with another liquid B. The mole fraction of B is 0.2 and the total vapour pressure of the solution is 84 torr at 27 C. The vapour pressure of pure liquid B at 27 C is (a) 14 torr (b) 56 torr (c) 70 torr (d) 140 torr 116. At 40 C the vapour pressure of pure liquids, benzene and toluene, are 160 mm Hg and 60 mm Hg respectively. At the same temperature, the vapour pressure of an equimolar solution of the two liquids, assuming the ideal solution should be (a) 140 mm Hg (b) 110 mm Hg (c) 220 mm Hg (d) 100 mm Hg 117. One mole of sugar is dissolved in two moles of water. The vapour pressure of the solution relative to that of pure water is (a) 2/3 (b) 1/3 (c) 3/2 (d) 1/ The vapour pressure of benzene at 80 C is lowered by 10 mm by dissolving 2 g of a non-volatile substance in 78 g of benzene. The vapour pressure of pure benzene at 80 C is 750 mm. The molecular mass of the substance will be (a) 15 g mol 1 (b) 150 g mol 1 (c) 1500 g mol 1 (d) 148 g mol Vapour pressure of CCl 4 at 25 C is 143 mm of Hg. 0.5 g of a non-volatile solute (mol. wt. 65) is dissolved in 100 ml CCl 4. Find the vapour pressure of the solution. (Density of CCl g/cm 3 ) (a) mm (b) mm (c) mm (d) mm 120. The vapour pressure of a solution increases when (a) the temperature is raised (b) the volume is increased (c) the number of moles of the solute is increased (d) the temperature is lowered.