Free NEET Chemistry multiple-choice questions on Conductance in Solutions. Attempt each question and reveal the answer with a full explanation.
The limiting molar conductivity of CaCl 2 at infinite dilution is calculated as: Ca 2+ + 2 Cl - Ca 2+ + Cl - 2 Ca 2+ + Cl - ( Ca 2+ + Cl - )/2 Which of the following factors does NOT affect the molar conductivity of an electrolytic solution? The dimensions of the electrodes Temperature Nature of the electrolyte Concentration of the electrolyte The unit of equivalent conductivity is: S cm 2 eq -1 S cm -2 eq -1 S -1 cm 2 eq cm 2 eq -1 As the temperature of an electrolytic solution increases, its molar conductivity generally: Increases due to decrease in viscous forces Decreases due to increase in ionic collisions Increases due to increase in hydration of ions Remains constant as concentration is unchanged The specific conductance of a 0.1 N KCl solution at 23 C is 0.012 -1 cm -1 . The resistance of cell containing the solution at the same temperature was found to be 55 . The cell constant is: 0.66 cm -1 0.91 cm -1 1.12 cm -1 4.58 cm -1 Which of the following factors has the greatest effect on the low ionic mobility of Li + in aqueous solution compared to other alkali metals? High degree of hydration Small atomic mass High ionization enthalpy Low lattice energy The unit of resistivity ( ) of an electrolytic solution is: cm -1 cm -1 S cm 2 mol -1 cm -1 The conductivity of 0.001 M acetic acid is 4 10 -5 S cm -1 . Its molar conductivity is: 40 S cm 2 mol -1 4 S cm 2 mol -1 400 S cm 2 mol -1 0.04 S cm 2 mol -1 A conductivity cell has a distance of 2 cm between the electrodes and an area of cross-section 4 cm 2 . Its cell constant is: 0.5 cm -1 2.0 cm -1 8.0 cm -1 0.25 cm -1 According to Kohlrausch's law, the limiting molar conductivity of Ca 3(PO 4) 2 is: 3 Ca 2+ + 2 PO 4 3- 2 Ca 2+ + 3 PO 4 3- Ca 2+ + PO 4 3- 3 Ca 2+ + PO 4 3- If the specific conductivity of a 0.01 M KCl solution is 1.4 10 -3 S cm -1 , and the resistance is 700 , the cell constant is: 0.98 cm -1 0.50 cm -1 1.96 cm -1 1.40 cm -1 The variation of molar conductivity m with c for a strong electrolyte is represented by the equation: m = m - A c m = m + A c m = A c m = m / A c The unit of molar conductivity is: S cm 2 mol -1 S cm -1 mol -1 S cm 2 mol cm 2 mol -1 Kohlrausch's law states that at infinite dilution: Each ion makes a definite contribution to molar conductivity of electrolyte irrespective of nature of other ion Molar conductivity of all electrolytes is same Specific conductance of all electrolytes is same Solubility of sparingly soluble salts is constant At 25 C molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm -1 cm 2 mol -1 and at infinite dilution its molar conductance is 238 ohm -1 cm 2 mol -1 . The degree of ionisation of ammonium hydroxide at the same concentration and temperature is 2.080% 20.800% 4.008% 40.800% The conductivity of centimolar solution of KCl at 25 C is 0.0210 ohm -1 cm -1 and the resistance of the cell containing the solution at 25 C is 60 ohm . The value of cell constant is 1.34 cm -1 3.28 cm -1 1.26 cm -1 3.34 cm -1 If the molar conductivity ( m) of a 0.050 mol L -1 solution of a monobasic weak acid is 90 S cm 2 mol -1 , its extent (degree) of dissociation will be [Assume + = 349.6 S cm 2 mol -1 and - = 50.4 S cm 2 mol -1 .] 0.215 0.115 0.125 0.225 If the limiting molar conductivities of NaCl , HCl and CH 3COONa are 126.4 , 425.9 and 91.0 S cm 2 mol -1 respectively, what is m for CH 3COOH ? 390.5 S cm 2 mol -1 425.5 S cm 2 mol -1 290.5 S cm 2 mol -1 540.5 S cm 2 mol -1 Calculate the molar conductivity at infinite dilution for Al 2(SO 4) 3 given Al 3+ = 189 S cm 2 mol -1 and SO 4 2- = 160 S cm 2 mol -1 . 858 S cm 2 mol -1 349 S cm 2 mol -1 509 S cm 2 mol -1 698 S cm 2 mol -1 The plot of molar conductivity ( m ) versus the square root of concentration ( c ) for a weak electrolyte like acetic acid is: A curve that increases steeply at low concentrations A straight line with negative slope A straight line with positive slope A horizontal line Which of the following is true regarding specific conductivity ( ) upon dilution of an electrolytic solution? It decreases because the number of ions per unit volume decreases It increases because the total number of ions increases It increases because the mobility of ions increases It remains constant because it depends only on the nature of the electrolyte Which of the following graphs correctly represents the conductometric titration of a strong acid ( HCl ) with a strong base ( NaOH )? A V-shaped curve with the minimum at the equivalence point A continuously rising curve A continuously falling curve A horizontal line that rises after the equivalence point Which of the following units represents the cell constant of a conductivity cell? cm -1 -1 cm -1 cm S cm 2 mol -1 For an electrolytic solution of Al 2(SO 4) 3 , the relationship between molar conductivity ( m ) and equivalent conductivity ( eq ) is: m = 6 eq m = eq / 6 m = 3 eq m = 2 eq The molar conductivity of 0.025 mol L -1 methanoic acid is 46.1 S cm 2 mol -1 . If m for H + is 349.6 and HCOO - is 54.6 S cm 2 mol -1 , the degree of dissociation ( ) is: 0.114 0.228 0.057 0.500 The molar conductivity of NH 4OH at infinite dilution can be calculated using the values of m for which set of electrolytes? Ba(OH) 2 , NH 4Cl and BaCl 2 NH 4Cl , NaCl and NaOH NH 4Cl , HCl and NaOH NaOH , NaCl and NH 4Cl Which of the following will have the highest molar conductivity at infinite dilution? H + Li + Na + K + In conductometric titrations, when a strong acid like HCl is titrated with a strong base like NaOH , the conductance initially: Decreases sharply Increases sharply Remains constant Increases then decreases The molar conductivity of a 0.1 M solution of BaCl 2 is found to be 230 S cm 2 mol -1 at 298 K . What is its equivalent conductivity? 115 S cm 2 eq -1 460 S cm 2 eq -1 230 S cm 2 eq -1 57.5 S cm 2 eq -1 Which of the following aqueous solutions will have the highest electrical conductivity? 0.1 M Al 2(SO 4) 3 0.1 M NaCl 0.1 M MgCl 2 0.1 M CH 3COOH For a strong electrolyte, the plot of molar conductivity ( m ) vs. c is a straight line. The intercept on the m axis gives: Limiting molar conductivity Cell constant Specific conductance Degree of dissociation The molar conductivity of a 0.01 M solution of BaCl 2 is 230 S cm 2 mol -1 . The conductivity ( ) of the solution is: 2.3 10 -3 S cm -1 2.3 S cm -1 230 S cm -1 0.023 S cm -1 Which of the following orders of molar conductivity at infinite dilution is correct for the alkali metal ions in aqueous solution? K + > Na + > Li + Li + > Na + > K + Na + > Li + > K + Li + > K + > Na + The molar conductivity of a 0.5 mol/dm 3 solution of AgNO 3 with electrolytic conductivity of 5.76 10 -3 S cm -1 at 298 K is: 11.52 S cm 2 mol -1 2.88 S cm 2 mol -1 0.0115 S cm 2 mol -1 1152 S cm 2 mol -1 If the resistance of a conductivity cell containing 0.1 M KCl is 100 and the cell constant is 1.2 cm -1 , the resistivity ( ) of the solution is: 83.3 cm 120 cm 1.2 cm 0.012 cm When the concentration of an electrolytic solution is decreased (dilution), the specific conductivity ( ) and molar conductivity ( m ) change as follows: decreases, m increases increases, m decreases Both increase Both decrease In aqueous solution, which of the following alkali metal ions has the highest ionic mobility? Cs + Rb + K + Li + According to the Debye-Hückel-Onsager equation m = m - A c , the constant ' A ' for a given solvent and temperature depends on: The type of electrolyte (charges on ions) The concentration of the electrolyte The molar mass of the electrolyte The solubility of the electrolyte The correct order of ionic mobility for the following alkali metal ions in aqueous solution is: Li + < Na + < K + < Rb + Rb + < K + < Na + < Li + Li + < Rb + < K + < Na + Na + < Li + < K + < Rb + Which of the following statements correctly distinguishes between metallic conduction and electrolytic conduction? Electrolytic conduction involves the transfer of matter, whereas metallic conduction does not. Metallic conduction increases with increasing temperature, whereas electrolytic conduction decreases. Electrolytic conduction follows Ohm's law, but metallic conduction does not. In metallic conduction, chemical changes occur at the surface. The limiting molar conductivity for H 2O can be determined using Kohlrausch's law by using the m values of: HCl, NaOH and NaCl HCl, NaOH and BaCl 2 H 2SO 4, Ca(OH) 2 and CaCl 2 CH 3COOH, NaOH and CH 3COONa Why does iron rust faster in seawater than in freshwater? The dissolved salts in seawater increase the conductivity of the electrolyte. Seawater has a higher concentration of dissolved oxygen. Seawater is more acidic than freshwater. The salt reacts directly with iron to form iron(III) chloride. Which of the following electrolytic solutions has the lowest limiting molar conductivity ( m ) at 298 K ? LiCl NaCl KCl HCl The limiting molar conductivity of CH 3COONH 4 can be calculated from the limiting molar conductivities of which set of electrolytes? CH 3COONa, NH 4Cl, NaCl CH 3COOH, NH 3, H 2O CH 3COONa, NH 4OH, NaOH CH 3Cl, NH 4Cl, HCl Which of the following describes the relationship between conductance ( G ) and resistance ( R )? G = 1/R G = R G = R G = R 2 The molar conductivity of a solution of a strong electrolyte increases slightly with dilution because: Interionic attractions decrease The number of ions increases The degree of ionization increases Viscosity of the solvent increases The resistance of a conductivity cell containing 0.05 M NaOH solution is 50 . If the cell constant is 0.5 cm -1 , the specific conductivity ( ) is: 0.01 S cm -1 0.1 S cm -1 25 S cm -1 0.001 S cm -1 The correct order of the mobility of the alkali metal ions in aqueous solution is:- Li+ > Na+ > K+ > Rb+ Na+ > K+ > Rb+ > Li+ K+ > Rb+ > Na+ > Li+ Rb+ > K+ > Na+ > Li+ The equivalent conductance of M 32 solution of a weak monobasic acid is 8.0 mho cm 2 and at infinite dilution is 400 mho cm 2 , The dissociation constant of this acid is - 1.25 10 -4 1.25 10 -5 1.25 10 -6 6.25 10 -4 Given that m = 133.4 ( AgNO3 ); m = 149.9 ( KCl ); m = 144.9 , S ,cm 2 ,mol -1 ( KNO3 ); the molar conductivity at infinite dilution for AgCl is 132 , S ,cm 2 ,mol -1 140 , S ,cm 2 ,mol -1 138 , S ,cm 2 ,mol -1 134 , S ,cm 2 ,mol -1 The molar conductance of NaCl, HCl and CH 3COONa at infinite dilution are 126.45, 426.16 and 91.0 S cm 2 mol -1 respectively. The molar conductance of CH 3COOH at infinite dilution is. Choose the right option for your answer. 390.71 S cm 2 mol -1 698.28 S cm 2 mol -1 540.48 S cm 2 mol -1 201.28 S cm 2 mol -1 The molar conductivity of 0.007 M acetic acid is 20 S cm 2 mol -1 . What is the dissociation constant of acetic acid? Choose the correct option. [ H+ = 350 S cm 2 mol -1 CH3COO - = 50 S cm 2 mol -1 ] 2.50 10 -4 mol L -1 1.75 10 -5 mol L -1 2.50 10 -5 mol L -1 1.75 10 -4 mol L -1 The solubility product of a sparingly soluble salt AB is K sp . The relationship between its molar conductivity at infinite dilution m and specific conductivity in its saturated solution is: K sp = [1000 / m ] 2 K sp = [ / 1000 m ] 2 K sp = 1000 / m K sp = [ m / 1000 ] 2 The conductometric titration of a weak acid ( CH 3COOH ) with a strong base ( NaOH ) is best represented by which of the following curves? Conductance initially decreases slightly, then increases slowly, and finally increases sharply after the equivalence point. Conductance decreases sharply and then remains constant. Conductance increases linearly from start to finish. Conductance remains constant and then decreases sharply. Which statement is true regarding the molar conductivity ( m ) of HCl compared to KCl at the same concentration in water? m(HCl) > m(KCl) because H + has higher mobility due to Grotthuss mechanism m(KCl) > m(HCl) because K + is larger and carries more charge m(HCl) = m(KCl) because both are 1:1 electrolytes m(KCl) > m(HCl) because Cl - is common to both The molar conductivity of a 0.01 M solution of a weak acid is 16.5 S cm 2 mol -1 . If its molar conductivity at infinite dilution is 390.5 S cm 2 mol -1 , the degree of dissociation is approximately: 0.042 0.422 0.016 0.165 In a conductometric titration of a strong acid ( HCl ) with a weak base ( NH 4OH ), the conductance initially decreases and then: Remains almost constant. Increases sharply. Decreases further. Drops to zero. The molar conductivity of 0.007 mol L -1 acetic acid is 20 S cm 2 mol -1 . What is the dissociation constant of acetic acid if m for CH 3COOH is 400 S cm 2 mol -1 ? 1.75 10 -5 mol L -1 2.50 10 -5 mol L -1 1.50 10 -4 mol L -1 1.25 10 -5 mol L -1 If the molar conductivity of Al 3+ and SO 4 2- are 1 and 2 respectively, the limiting equivalent conductivity of Al 2(SO 4) 3 is: ( 1 / 3) + ( 2 / 2) 2 1 + 3 2 1 + 2 3 1 + 2 2 For a salt XY, which is a strong electrolyte, the plot of m versus c has a slope of -90.0 S cm 2 mol -3/2 L 1/2 at 298 K. At 0.01 M concentration of XY, the value of m is 145.0 S cm 2 mol -1 . The limiting molar conductivity of Y- ion ( 0 Y- , in S cm 2 mol -1 ) at 298 K will be (Given : 0 X+ = 74.0 S cm 2 mol -1 ) 80.0 100.0 90.0 76.0 The unit of specific conductivity (cell constant is l/A ) is: S cm -1 S cm 2 mol -1 S cm 2 cm Which equation represents the Kohlrausch's law for a strong electrolyte? m = m - A c m = m + A c m = m / c m = m - Ac Limiting molar conductivity of Mg(OH) 2 can be expressed as: Mg 2+ + 2 OH - Mg 2+ + OH - 2 Mg 2+ + OH - 1 2 Mg 2+ + OH -