Free NEET Chemistry multiple-choice questions on Raoult's Law. Attempt each question and reveal the answer with a full explanation.
When two liquids A and B are mixed, the resulting solution shows a negative deviation from Raoult's law. This implies that: The A-B intermolecular forces are stronger than A-A and B-B forces The A-B intermolecular forces are weaker than A-A and B-B forces The mixing process is endothermic ( H mix > 0 ) The total volume of the solution is greater than the sum of the volumes of A and B The boiling point of an azeotropic mixture of water and ethanol is lower than that of both water and ethanol. This mixture shows: Positive deviation from Raoult's Law Negative deviation from Raoult's Law Ideal behavior No deviation from Raoult's Law In a mixture of A and B , components show negative deviation as: ΔV mix is negative ΔH mix is positive A-B interaction is weaker than A-A and B-B interactions Total vapour pressure is higher than predicted by Raoult's Law 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: 72 torr 140 torr 68 torr 20 torr Azeotropic mixtures cannot be separated into pure components by fractional distillation because: The liquid and vapour phases have the same composition The components react chemically The boiling point of components is too high One component is non-volatile What is the relative lowering of vapour pressure for a solution containing n 1 moles of solvent and n 2 moles of a non-volatile solute? n 2 n 1 + n 2 n 1 n 1 + n 2 n 2 n 1 n 1 + n 2 n 2 The boiling point of water is lower on a mountain top compared to sea level because: Atmospheric pressure is lower Temperature is lower Humidity is higher The air is thinner and contains less oxygen For a solution of a non-volatile solute in a liquid solvent, which form of Raoult's law is correct? P s = P o X solvent P s = P o X solute P o - P s = X solvent P s = P o / X solvent Which of the following statements is correct regarding a solution of two components A and B exhibiting positive deviation from Raoult's law? Intermolecular forces between A-A and B-B are stronger than those between A-B V mix is negative H mix is negative Intermolecular forces between A-A and B-B are weaker than those between A-B For a solution of a non-volatile solute, the relative lowering of vapour pressure is equal to: Mole fraction of the solute Mole fraction of the solvent Molality of the solution Molarity of the solution If P o and P are the vapour pressures of the pure solvent and its solution at a given temperature respectively, and n 1 and n 2 are the mole fractions of the solvent and solute respectively, then Raoult's law is given by: P = P o n 1 P = P o n 2 P o - P = P o n 1 P = P o(n 1/n 2) Which of the following pairs shows a negative deviation from Raoult's Law? Chloroform + Acetone Ethanol + Acetone Benzene + Toluene Carbon tetrachloride + Methanol In a mixture showing positive deviation from Raoult's law, the intermolecular forces between A-B molecules compared to A-A and B-B are: Weaker Stronger Identical Zero An azeotropic mixture of two liquids has a boiling point lower than either of them when it shows: Large positive deviation from Raoult's law Large negative deviation from Raoult's law No deviation from Raoult's law High solubility Which of the following is true for the vapour pressure of a solution containing a non-volatile solute compared to the pure solvent? The vapour pressure of the solution is always lower. The vapour pressure of the solution is always higher. The vapour pressure remains the same. The vapour pressure of the solution is higher at lower temperatures only. Azeotropic mixtures are . Constant boiling mixtures Mixtures of two solids Those which can be separated by fractional distillation Those which obey Raoult's Law A mixture of components A and B shows a negative deviation from Raoult's law when: ΔH mix < 0 and ΔV mix < 0 ΔH mix > 0 and ΔV mix > 0 ΔH mix = 0 and ΔV mix = 0 ΔH mix < 0 and ΔV mix > 0 An azeotropic mixture of two liquids boils at a lower temperature than either of them when: It shows a large positive deviation from Raoult's law It shows a large negative deviation from Raoult's law It is an ideal solution It shows no deviation from Raoult's law Which of the following liquid pairs constitutes a Nearly Ideal Solution? Chlorobenzene and Bromobenzene Water and Nitric acid Acetone and Carbon disulfide Ethanol and Water When 1.0 mol of a non-volatile solute is dissolved in 9.0 mol of a solvent, the relative lowering of vapor pressure is: 0.10 0.11 0.90 1.00 When n -hexane and n -heptane are mixed, which of the following is true regarding the thermodynamics of the process? H mix = 0, V mix = 0 H mix > 0, V mix > 0 H mix < 0, V mix < 0 H mix = 0, V mix < 0 For a solution of a non-volatile solute, the relative lowering of vapor pressure is 0.2 . What is the mole fraction of the solvent? 0.8 0.2 0.5 0.6 Which of the following mixtures shows a negative deviation from Raoult's law because of the formation of a hydrogen bond between the two components? Chloroform and Acetone Ethanol and Water Benzene and Toluene Carbon tetrachloride and Chloroform 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 mole of P and 2 mole of Q would be :- 68 torr 140 torr 72 torr 20 torr A solution of acetone is ethanol:- Shows a negative deviation from Raoult's law Shows a positive deviation from Raoult's law Behaves like a near ideal solution Obeys Raoult's law For an ideal solution, the correct option is : mix ,G = 0 at constant T and P mix ,S = 0 at constant T and P mix ,V 0 at constant T and P mix ,H = 0 at constant T and P The mixture that forms maximum boiling azeotrope is: Heptane + Octane Water + Nitric acid Ethanol + Water Acetone + Carbon disulphide 5 moles of liquid X and 10 moles of liquid Y make a solution having a vapour pressure of 70 torr. The vapour pressures of pure X and Y are 63 torr and 78 torr respectively. Which of the following is true regarding the described solution? The solution has volume greater than the sum of individual volumes. The solution shows positive deviation. The solution shows negative deviation. The solution is ideal. Mixture of chloroform and acetone forms a solution with negative deviation from Raoult’s law due to : Stronger intermolecular forces between chloroform molecules than those between chloroform and acetone molecules. Formation of hydrogen bonding between acetone and chloroform Repulsive forces. Increase in escaping tendency of molecules of each component. A solution of acetone in ethanol shows . Positive deviation from Raoult's law Negative deviation from Raoult's law No deviation from Raoult's law Behavior of an ideal solution Identify the incorrect statement regarding ideal solutions. S mix = 0 H mix = 0 V mix = 0 It obeys Raoult's law over the entire range of concentration The vapour pressure of benzene and toluene at 25 C are 75 ,mmHg and 22 ,mmHg respectively. A solution is prepared by mixing benzene and toluene in a molar ratio of 3:2 . What is the total vapour pressure of the solution? 53.8 mmHg 48.5 mmHg 97.0 mmHg 37.2 mmHg If the vapour pressure of pure water at 298 ,K is 23.8 ,mmHg and 50 ,g of urea ( NH 2CONH 2 ) is dissolved in 850 ,g of water, the relative lowering of vapour pressure is: 0.017 0.034 0.238 0.050 The boiling point of an azeotropic mixture of HNO 3 and H 2O is higher than that of both. This implies that: The solution shows negative deviation from Raoult's Law The solution shows positive deviation from Raoult's Law The solution is ideal The intermolecular forces A-B are weaker than A-A Which of the following mixtures will show a maximum in the boiling point-composition curve (maximum boiling azeotrope)? Chloroform + Acetone Ethanol + Water Benzene + Toluene n-Hexane + n-Heptane Consider the following diagram of the vapour pressure of two volatile liquids A and B . Which statement is correct regarding the point where the two lines intersect? The mole fraction of A and B in the liquid phase is such that their partial pressures are equal The liquid is a pure component The total pressure is at its maximum The solution is ideal For a non-ideal solution showing positive deviation from Raoult's law, which of the following is true? V mix > 0 and H mix > 0 V mix < 0 and H mix < 0 V mix = 0 and H mix = 0 V mix > 0 and H mix < 0 In a plot of vapour pressure versus temperature, which curve represents the solution compared to the pure solvent? The solution curve lies below the solvent curve The solution curve lies above the solvent curve The curves intersect at the boiling point The curves are identical for ideal solutions For a solution of two volatile components A and B , the total vapour pressure is given by P = 120 - 80X B (in mmHg ), where X B is the mole fraction of B . The vapour pressure of pure A is: 120 mmHg 40 mmHg 80 mmHg 200 mmHg Which of the following statements about the composition of the vapour over an ideal 1:1 molar mixture of benzene ( P o = 12.8 kPa ) and toluene ( P o = 3.85 kPa ) is correct? The vapour will contain a higher percentage of benzene The vapour will contain a higher percentage of toluene The vapour will contain equal percentages of benzene and toluene The composition of vapour cannot be determined Which of the following is correct regarding a solution of Chloroform and Acetone? V mix < 0 V mix > 0 H mix > 0 It obeys Raoult's Law At 80 C , the vapour pressure of pure liquid A is 520 mm Hg and that of pure liquid B is 1000 mm Hg . If a mixture solution of A and B boils at 80 C and 1 atm pressure, the mole fraction of A in the mixture is ( 1 atm = 760 mm Hg ): 0.50 0.48 0.34 0.52 For a solution of two volatile components A and B , the total vapour pressure P is given by P = 254 - 119 X A . The vapour pressure of pure B is: 254 135 119 150 A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of 290 mm at 300 K . The vapour pressure of propyl alcohol is 200 mm . If the mole fraction of ethyl alcohol is 0.6 , its vapour pressure (in pure state) at the same temperature will be: 350 mm 300 mm 700 mm 250 mm Which concentration term is most useful in relating the physical properties of solutions, like vapour pressure, to the concentration of the solution? Mole fraction Molarity Mass percentage ppm When ethanol and cyclohexane are mixed, the H -bonds between ethanol molecules break. What type of deviation from Raoult's law does this mixture show? Positive deviation Negative deviation No deviation Initial positive then negative deviation Which of the following plots represents a solution showing positive deviation from Raoult's law? The total vapour pressure curve is higher than that of an ideal solution The total vapour pressure curve is lower than that of an ideal solution The total vapour pressure is a straight line The total vapour pressure curve passes through the origin For an ideal liquid-liquid solution of A and B , if P o A = 400 ,mmHg , P o B = 600 ,mmHg , and the mole fraction of A in the solution is 0.4 , the total vapour pressure is: 520 ,mmHg 480 ,mmHg 500 ,mmHg 560 ,mmHg In a mixture of chloroform and acetone, the A-B interactions (hydrogen bonding) are stronger than A-A and B-B interactions. This result in: Decrease in vapor pressure (Negative deviation) Increase in vapor pressure (Positive deviation) No change in vapor pressure Constant boiling point regardless of composition The correct option for the value of vapour pressure of a solution at 45 C with benzene to octane in molar ratio 3:2 is (At 45 C , vapour pressure of benzene is 280 ,mmHg and that of octane is 420 ,mmHg ): 336 ,mmHg 350 ,mmHg 168 ,mmHg 380 ,mmHg The following graph represents the variation of vapour pressure with mole fraction for a binary solution. Which of the following statements is true for the point P ? The solution at point P acts as a maximum boiling azeotrope The solution at point P acts as a minimum boiling azeotrope The solution at point P follows Raoult's Law perfectly The solution components at point P cannot be separated by fractional distillation At 300 ,K , the vapour pressure of pure water is 23.8 ,mmHg . If 50 ,g of urea ( NH 2CONH 2 ) is dissolved in 850 ,g of water, what is the vapour pressure of the solution? 23.4 ,mmHg 22.8 ,mmHg 23.8 ,mmHg 24.2 ,mmHg Which of the following describes the behavior of a solution of phenol and aniline? Negative deviation from Raoult's law due to H-bonding Positive deviation from Raoult's law due to H-bonding Ideal behavior Negative deviation due to dipole-dipole repulsion For a solution of two volatile liquids A and B , the vapour pressure of the pure components are P o A and P o B . If X A is the mole fraction of component A in the liquid phase and Y A is the mole fraction of component A in the vapour phase, the relationship between Y A , X A , P o A , and P total is given by: Y A = X A P o A / P total Y A = X A P total / P o A Y A = P o A / (X A P total ) Y A = X A + P o A / P total For a binary mixture of Chloroform and Acetone, which of the following is true regarding the volume of mixing ( V mix )? V mix < 0 V mix > 0 V mix = 0 V mix depends on temperature only A liquid mixture that boils at a constant temperature without changing its composition is called: An azeotrope An ideal solution A saturated solution A supersaturated solution Liquids A and B form an ideal solution. At a certain temperature, the vapour pressure of pure A is 100 ,mmHg and pure B is 200 ,mmHg . If the solution contains 1 ,mol of A and 4 ,mols of B , the total vapour pressure is: 180 mmHg 150 mmHg 120 mmHg 160 mmHg For an ideal solution, the graph of total vapour pressure ( P total ) against the mole fraction of a component ( X B ) is expected to be: A straight line with a slope equal to (P o B - P o A) A curved line passing through the origin A straight line parallel to the X-axis A straight line with a slope equal to P o A Which of the following describes the behavior of a mixture of Carbon disulfide ( CS 2 ) and Acetone? Positive deviation from Raoult's law Negative deviation from Raoult's law Ideal solution Forms a maximum boiling azeotrope The vapor pressure of water at 20 C is 17.5 mm Hg . If 18 g of glucose ( C 6H 12 O 6 ) is added to 178.2 g of water at 20 C , the vapor pressure of the resulting solution will be: 17.325 mm Hg 17.675 mm Hg 15.750 mm Hg 16.500 mm Hg For a binary ideal solution, the variation of total vapor pressure ( P ) with the mole fraction of component 1 ( X 1 ) is given by: P = P°2 + (P°1 - P°2)X1 P = P°1 + (P°2 - P°1)X1 P = P°1X1 + P°2(1+X1) P = P°1/X1 + P°2/X2 During the mixing of two liquids A and B to form an ideal solution, which of the following thermodynamic properties is zero? ΔV mix and ΔH mix ΔG mix ΔS mix Both ΔG mix and ΔS mix The azeotropic mixture of 95.4 % ethanol and 4.6 % water by mass is a: Minimum boiling azeotrope Maximum boiling azeotrope Ideal solution Saturated solution Which of the following shows a large positive deviation from Raoult's law due to the breaking of hydrogen bonds? Ethanol and Cyclohexane Chloroform and Acetone Benzene and Toluene Phenol and Aniline A solution of A and B follows Raoult's law perfectly. If the vapor pressure of pure A and B are 100 and 200 mm Hg respectively, what is the vapor pressure of a solution with X A = 0.4 ? 160 mm Hg 140 mm Hg 150 mm Hg 120 mm Hg A mixture of HCl and water forms a maximum boiling azeotrope. This means: The A-B interactions are stronger than A-A and B-B The A-B interactions are weaker than A-A and B-B The solution is ideal H mix is positive Which condition is characteristic of an ideal solution? H mix = 0 and V mix = 0 H mix > 0 and V mix > 0 H mix < 0 and V mix < 0 G mix = 0 In a non-ideal solution showing negative deviation, the vapor pressure is lower than expected because: A-B interactions are stronger than A-A and B-B interactions A-B interactions are weaker than A-A and B-B interactions The solute is non-volatile The solution behaves like a pure solvent The boiling point of an azeotropic mixture of water and nitric acid is 393.5 ,K , while the boiling point of pure water is 373 ,K and pure nitric acid is 359 ,K . This mixture is a: Maximum boiling azeotrope showing negative deviation Minimum boiling azeotrope showing positive deviation Maximum boiling azeotrope showing positive deviation Minimum boiling azeotrope showing negative deviation A solution of two volatile liquids A and B shows a large positive deviation from Raoult's law. What happens to the volume and enthalpy upon mixing? V mix > 0, H mix > 0 V mix < 0, H mix < 0 V mix = 0, H mix = 0 V mix > 0, H mix < 0 For an ideal solution of two volatile components A and B , which of the following thermodynamic conditions is NOT zero? S mix H mix V mix P = P obs - P Raoult If the vapour pressure of pure liquids A and B are 450 and 700 ,mmHg respectively at 350 ,K , find the composition of the liquid mixture if total vapour pressure is 600 ,mmHg . X A = 0.4, X B = 0.6 X A = 0.6, X B = 0.4 X A = 0.5, X B = 0.5 X A = 0.3, X B = 0.7 A solution contains 1 ,mol of water and 4 ,mol of ethanol. The vapor pressure of the solution is 40 ,mmHg . If the vapor pressure of pure ethanol is 45 ,mmHg , find the vapor pressure of pure water at that temperature (Assume ideal behavior). 20 mmHg 40 mmHg 10 mmHg 35 mmHg Mixing of n -heptane and ethanol shows a positive deviation from Raoult's law. This is because: Ethanol molecules are held by H-bonds which are weakened by n -heptane New strong H-bonds are formed between n -heptane and ethanol The mixture forms an ideal solution The volume of the solution decreases upon mixing When 1 ,mole of a non-volatile solute is dissolved in 5 ,moles of a solvent, the vapor pressure of the solution relative to that of the pure solvent is: 5/6 1/5 1/6 4/5 A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressures of the pure hydrocarbons at 20 C are 440 mm Hg for pentane and 120 mm Hg for hexane. The mole fraction of pentane in the vapour phase would be- 0.200 0.478 0.549 0.786 Which of the following statement about the composition of the vapour over an ideal a 1 : 1 molar mixture of benzene and toluene is correct? Assume that the temperature is constant at 25 C . (Given : Vapour Pressure Data at 25 C , benzene = 12.8 kPa , Toluene = 3.85 kPa ) The vapour will contain a higher percentage of benzene The vapour will contain a higher percentage of toluene The vapour will contain equal amounts of benzene and toluene Not enough information is given to make a prediction What is the mole fraction of the solvent in a solution where the relative lowering of vapour pressure is 0.2 ? 0.8 0.2 1.0 0.5 Toluene in the vapour phase is in equilibrium with a solution of benzene and toluene having mole fraction of toluene 0.50 If vapour pressure of pure benzene is 119 torr and that of toluene is 37.0 torr at the same temperature, mole fraction of toluene in vapour phase will be : 0.325 0.462 0.237 0.506 The mixture which shows positive deviation from Raoult’s law is Benzene + Toluene Acetone + Chloroform Chloroethane + Bromoethane Ethanol + Acetone The correct option for the value of vapour pressure of a solution at 45°C with benzene to octane in molar ratio 3 : 2 is : [At 45°C vapour pressure of benzene is 280 mm Hg and that of octane is 420 mm Hg. Assume Ideal gas] 168 mm of Hg 336 mm of Hg 350 mm of Hg 160 mm of Hg The vapor pressure of pure benzene at a certain temperature is 640 mm Hg . A non-volatile non-electrolyte solid weighing 2.175 g is added to 39.0 g of benzene. The vapor pressure of the solution is 600 mm Hg . What is the molecular weight of the solid? 65.25 g/mol 130.5 g/mol 32.6 g/mol 48.5 g/mol Two liquids X and Y form an ideal solution. At 300 ,K , the vapour pressure of a solution containing 1 ,mol of X and 3 ,mol of Y is 550 ,mmHg . At the same temperature, if 1 ,mol of Y is further added to this solution, the vapour pressure of the solution increases by 10 ,mmHg . The vapour pressure of pure X and Y are: 400 and 600 mmHg 300 and 500 mmHg 500 and 600 mmHg 200 and 400 mmHg The vapour pressure of a solution of 2.0 ,g of a non-volatile solute in 100 ,g water at 100 C is 755 ,mmHg . What is the molar mass of the solute? 135 g/mol 60 g/mol 180 g/mol 342 g/mol Two liquids A and B form an ideal solution at 300 K , the vapour pressure of a solution containing 1 mol of A and 3 mol of B is 550 mm Hg . At the same temperature, if 1 mol of B is added to this solution, the vapour pressure of the solution increases by 10 mm Hg . The vapour pressure of pure A and B in their pure state are respectively: 400, 600 600, 400 500, 500 300, 700 An ideal solution contains two volatile liquids A ( P o A = 100 ,mmHg ) and B ( P o B = 200 ,mmHg ). If the mole fraction of A in the liquid phase is 0.5 , what is the mole fraction of A in the vapour phase? 0.33 0.50 0.67 0.25 A mixture of 2 ,mol of A and 3 ,mol of B has a total vapour pressure of 300 ,torr . When 1 ,mol of A is added, the total vapour pressure increases to 310 ,torr . Calculate P o A and P o B . P o A = 330, P o B = 280 P o A = 280, P o B = 330 P o A = 300, P o B = 300 P o A = 350, P o B = 250 The vapour pressure of pure liquid A at 300 K is 100 mm Hg . When 2 moles of liquid B are added to 3 moles of A , the vapour pressure of the solution becomes 80 mm Hg . The vapour pressure of pure B is ( A, B form ideal solution): 50 mm Hg 80 mm Hg 100 mm Hg 40 mm Hg When n -hexane and n -heptane are mixed, the resulting solution is almost ideal. This is because: The intermolecular attractions between A-A , B-B , and A-B are nearly identical The molecules are polar and interact strongly The solution shows a large positive deviation The solution shows a large negative deviation A solution contains 1 mol of liquid A and 2 mol of liquid B . If P o A = 120 mm Hg and P o B = 180 mm Hg , find the mole fraction of A in the vapour phase. 0.25 0.33 0.50 0.75 A solution of 1 mol of A and 2 mol of B has P total = 150 mm Hg . If P o A = 100 mm Hg , find P o B . 175 mm Hg 150 mm Hg 200 mm Hg 125 mm Hg A solution is prepared by mixing 1 ,mol of benzene and 3 ,mol of toluene. The mole fraction of benzene in the vapour phase ( Y B ) is: (Given P o benzene = 100 ,torr , P o toluene = 60 ,torr ) 0.357 0.250 0.500 0.420 Assertion A: For an ideal solution formed by mixing liquids P and Q, mix H = 0 and mix V = 0 Reason R: No interactions occur between P and Q In the light of the above statements, choose the most appropriate answer from the options given below. Both A and R are correct and R is the correct explanation of A Both A and R are correct but R is NOT the correct explanation of A A is correct but R is not correct A is not correct but R is correct Consider the following statements about the solutions formed by mixing two liquids. A. An ideal solution thus formed obeys Raoult's law throughout the composition range. B. Mixture of chloroform and acetone shows negative deviation from Raoult's law. C. Mixture of aniline and phenol shows positive deviation from Raoult's law. A and B only B and C only A only A and C only