In Class 12 Boards there will be Case studies and Passage Based Questions will be asked, So practice these types of questions. Study Rate is always there to help you. Free PDF Downloads of CBSE Class 12 Chemistry Chapter 3 Electrochemistry Case Study and Passage-Based Questions with Answers were Prepared Based on the Latest Exam Pattern. Students can solve NCERT Class 12 Chemistry Case Study Questions Electrochemistry to know their preparation level.
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In CBSE Class 12 Chemistry Paper, There will be a few questions based on case studies and passage-based as well. In that, a paragraph will be given, and then the MCQ questions based on it will be asked.
Electrochemistry Case Study Questions With Answers
Here, we have provided case-based/passage-based questions for Class 12 Chemistry Chapter 3 Electrochemistry
Case Study/Passage-Based Questions
Case Study 1:The study of the conductivity of electrolyte solutions is important for the development of electrochemical devices, for the characterization of the dissociation equilibrium of weak electrolytes, and for the fundamental understanding of charge transport by ions. The conductivity of the electrolyte is measured for electrolyte solution with concentrations in the range of 10–3 to 10–1 mol L–1, as a solution in this range of concentrations can be easily prepared. The molar conductivity (Λm)
of strong electrolyte solutions can be nicely fit by the Kohlrausch equation.
Λm = Λ°m – K √C …(i)
Where Λ°m is the molar conductivity at infinite dilution and C is the concentration of the solution. K is an empirical proportionality constant to be obtained from the experiment. The molar conductivity of weak electrolytes, on the other hand, is dependent on the degree of dissociation of the electrolyte. At the limit of a very dilute solution, the Ostwald dilution law is expected to be followed,
where CA is the analytical concentration of the electrolyte and Kd is the dissociation constant. The molar conductivity at infinite dilution can be decomposed into the contributions of each ion.
Where, λ+ and λ– are the ionic conductivities of positive and negative ions, respectively and v+ and v– are their stoichiometric coefficients in the salt molecular formula.
Which statement about the term infinite dilution is correct?
(a) Infinite dilution refers to a hypothetical situation when the ions are infinitely far apart.
(b) The molar conductivity at infinite dilution of NaCl can be measured directly in solution.
(c) Infinite dilution is applicable only to strong electrolytes.
(d) Infinite dilution refers to a real situation when the ions are infinitely far apart.
Answer: (a) Infinite dilution refers to a hypothetical situation when the ions are infinitely far apart.
Which of the following is a strong electrolyte in aqueous solution?
(a) HNO2 (b) HCN
(c) NH3 (d) HCl
Answer: (d) HCl
Which of the following is a weak electrolyte in aqueous solution?
(a) K2SO4 (b) Na3PO4
(c) NaOH (d) H2SO3
Answer: (d) H2SO3
If the molar conductivities at infinite dilution for NaI, CH3COONa and (CH3COO)2Mg are 12.69, 9.10 and 18.78 S cm2 mol–1 respectively at 25°C, then the molar conductivity of MgI2 at infinite dilution is
(a) 25.96 S cm2 , mol–1 (b) 390.5 S cm2 mol–1
(c) 189.0 S cm2 mol–1
(d) 3.89 × 10–2 S cm2 mol–1
Answer: (a) 25.96 S cm2 , mol–1
Which of the following is the correct order of molar ionic conductivities of the following ions in aqueous solutions?
- (a) Li+ < Na+ < K+ < Rb+
- (b) Li+ > Na+ > K+ > Rb+
- (c) Rb+ < Na+ < Li+ < K+
- (d) Li+ < Rb+< Na+ < K+
Answer: (a) Li+ < Na+ < K+ < Rb+
Case Study/Passage-Based Questions
Case Study 2: The concentration of potassium ions inside a biological cell is at least twenty times higher than the outside. The resulting potential difference across the cell is important in several processes such as the transmission of nerve impulses and maintaining the ion balance. A simple model for such a concentration cell involving a metal M is
M(s) |M+(aq.; 0.05 molar)||M+(aq; 1 molar)|M(s)
For the above cell,
- (a) Ecell = 0 ; ΔG > 0
- (b) Ecell > 0 ; ΔG < 0
- (c) Ecell < 0 ; ΔG° > 0
- (d) Ecell > 0 ; ΔG° = 0
Answer: (b) Ecell > 0 ; ΔG < 0
If the 0.05 molar solution of M+ is replaced by a 0.0025 molar M+ solution, then the magnitude of the cell potential would be
(a) 130 mV (b) 185 mV
(c) 154 mV (d) 600 mV
Answer: (c) 154 mV
The value of the equilibrium constant for a feasible cell reaction is
- (a) < 1
- (b) = 1
- (c) > 1
- (d) zero
Answer: (c) > 1
What is the emf of the cell when the cell reaction attains equilibrium?
(a) 1 (b) 0 (c) > 1 (d) < 1
Answer: (b) 0
The potential of an electrode change with change in
(a) concentration of ions in solution
(b) position of electrodes
(c) voltage of the cell
(d) all of these.
Answer: (a) concentration of ions in solution
Case Study 3: All chemical reactions involve the interaction of atoms and molecules. A large number of atoms/molecules are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such a large number conveniently, the mole concept was introduced. All electrochemical cell reactions are also based on the mole concept. For example, a 4.0 molar aqueous solution of NaCI is prepared and 500 mL of this solution is electrolysed. This leads to the evolution of chlorine gas at one of the electrodes. The amount of products formed can be calculated by using the mole concept.
(i) The total number of moles of chlorine gas evolved is
| (a) 0.5 | (b) 1.0 | (c) 1.5 | (d) 1.9 |
Answer: (b) 1.0
(ii) If cathode is a Hg electrode, then the maximum weight of amalgam formed from this solution is
| (a) 300 g | (b) 446 g | (c) 396 g | (d) 296 g |
Answer: (b) 446 g
(iii) In the electrolysis, the number of moles of electrons involved are
| (a) 2 | (b) 1 | (c) 3 | (d) 4 |
Answer: (a) 2
(iv) In electrolysis of aqueous NaCl solution when Pt electrode is taken, then which gas is liberated at cathode?
| (a) H2 gas | (b) C2 gas | (c) O2 gas | (d) None of these |
Answer: (a) H2 gas
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