Chemistry Test - 35

Correct Answer: C

Explanation: The passage clearly states that CFST describes how “when ligands approach the isolated metal ion, the ligand’s field splits the degenerated d-orbitals of the isolated metal ion into the states of higher and lower energy with a forbidden energy gap in between.” Option A is incorrect as ligands do affect the d-orbitals. Option B is wrong because ligands split, not degenerate, the d-orbitals. Option D is incorrect as the passage does not mention electron pairing or high-spin complexes in the context of CFST’s general statement.

(A) Aqueous solutions have water as the solvent. Correct (e.g., saltwater uses water as the solvent).

(B) Solid solutions can be liquid in nature. Incorrect. Solid solutions are homogeneous mixtures in the solid phase (e.g., alloys like Cu-Zn in brass). Liquid solutions exist (e.g., ethanol in water), but they are not called solid solutions.

(C) All solutions are homogeneous in nature. Correct. Solutions are defined as homogeneous mixtures with uniform composition.

(D) A solution is a mixture of two or more substances. Correct. A solution consists of a solute dissolved in a solvent. Thus, the correct statements are (A), (C), and (D). The answer is B ((A), (C), and (D) only).

(A) In a galvanic cell, the anode is the site of reduction. Incorrect. In a galvanic cell, oxidation occurs at the anode, and reduction occurs at the cathode.

(B) The cathode is the site of oxidation in an electrolytic cell. Incorrect. In an electrolytic cell, oxidation occurs at the anode, and reduction occurs at the cathode.

(C) In a galvanic cell, spontaneous redox reactions generate electrical energy. Correct. Galvanic cells convert chemical energy from spontaneous redox reactions into electrical energy.

(D) The standard electrode potential of a cell can be determined by the Nernst equation. Correct. The Nernst equation relates cell potential to standard electrode potential (E°), allowing calculation of E° under standard conditions (when E = E° at [ion] = 1 M).

Thus, the correct statements are (C) and (D). The answer is B ((C) and (D) only).

(A) Electrolytic cells are used for electroplating. Correct. Electrolytic cells drive non-spontaneous reactions, such as depositing metals (e.g., Cu or Ag) onto surfaces during electroplating.

(B) The cathode is positive, and the anode is negative in an electrolytic cell. Incorrect. In electrolytic cells, the cathode is negative (where reduction occurs), and the anode is positive (where oxidation occurs), due to the external power source.

(C) Electrolytic cells require an external power source to drive non-spontaneous reactions. Correct. An external voltage forces non-spontaneous redox reactions to occur.

(D) In electrolytic cells, reduction occurs at the anode. Incorrect. Reduction occurs at the cathode, and oxidation occurs at the anode.

Thus, the correct statements are (A) and (C). The answer is B ((A) and (C) only).

(A) The Nernst equation relates the cell potential to the concentration of ions in the solution. Correct. The Nernst equation (E = E° – (RT/nF)lnQ) relates cell potential to ion concentrations via the reaction quotient Q.

(B) The Nernst equation applies only to galvanic cells. Incorrect. It applies to both galvanic and electrolytic cells, as it describes electrode or cell potentials under any conditions.

(C) The Nernst equation can be used to calculate the electrode potential under non-standard conditions. Correct. It adjusts the standard potential (E°) for non-standard concentrations or temperatures.

(D) The Nernst equation is applicable only at standard temperature (25°C). Incorrect. The equation includes temperature (T) as a variable, allowing use at any temperature. Thus, the correct statements are (A) and (C). The answer is A ((A) and (C) only).

Molecular mass of glycerine = 92 g

Molecular mass of water = 18 g

No. of moles of glycerine = 46/92 = 0.5 moles

No. of moles of water = 36/18 = 2 moles

Thus, Mole fraction of glycerine = No. of moles of glycerine/(No. of moles of glycerine + No. of moles of water) = 0.5/(2 + 0.5)  = 0.20

12.5% w/w means 12.5 g in 100 g of solution.

Weight of solvent = 100 g – 12.5 g = 87.5 g.

Number of moles of sulphuric acid = 12.5/ 98 = 0.127 mol

⇒ molality = 0.127 x 1000/87.5 = 1.45 m

In this Cl^–  will oxidise to give Cl₂ ,Na⁺ reduction potential has lower potential than water reduction polenlid so water will reduce to give H₂.

Electrolysis of H₂SO₄

Cathode:-
2H⁺  +  2e^-  -  H₂    (Reduction)

Anode:-
4OH^-  -  2H₂O  +  O₂  + 4e^-  (Oxidation)

OH^- ions discharged at anode.