Chemistry: CUET Mock Test - 10 - CUET MCQ

An electrolytic cell is a type of electrochemical cell. An electrolytic cell converts electrical energy into chemical energy. Electrons flow from anode to cathode through the external supply in an electrolytic cell. In the solution, only ions flow and not the electrons.

To name this compound according to IUPAC conventions, follow these guidelines:
List the ligands first, in alphabetical order. The ligands here are ammonia (ammine in naming coordination entities) and chloride.
After the ligands, name the metal itself. The oxidation state of the metal is indicated in Roman numerals in parentheses right after the name of the metal.
The name ends with the counter ion(s) outside the coordination sphere.

Complex Ion:
[Co(NH₃)₅Cl]²⁺

Given:

• Ammonia (NH₃) is a neutral ligand, so its charge = 0

• Chloride ion (Cl⁻) has a charge = -1

• The overall charge on the complex ion is +2

Let the oxidation state of cobalt be x.
Now, using the formula:

x + (5 × 0) + (-1) = +2
x - 1 = +2
x = +3

So, the oxidation state of cobalt is +3.

There are two chloride ions (Cl⁻) outside the coordination sphere to balance the +2 charge of the complex ion.

IUPAC Name:
Pentaamminechloridocobalt(III) chloride

Due to high charge density on Co³⁺ and the presence of a strong field ligand (NH3), electrons in d-orbitals will pair up so unpaired electron (n) will be zero.

∴ Spin only magnetic moment = BM

= 0

Due to high charge density on Co3+ and the presence of a strong field ligand (NH3), electrons in d-orbitals will pair up.
[Co(NH₃)₅Cl]Cl₂ ⇒ Co³⁺ : [Ar]3d⁶4s⁰4p⁰

[Co(NH₃)₅Cl]Cl₂

In [Co(NH₃)₅Cl]Cl₂​, the coordination number of cobalt is the number of ligands directly bonded to it in the coordination sphere. There are five NH3 ligands and one Cl⁻  ligand, giving a coordination number of: 5+1=6.
Coordination number = total number of donating sites = 5 + 1 = 6

Complex Compound:
[Co(NH₃)₅Cl]Cl₂

Explanation:
The primary valence is the oxidation state of the central metal atom, which is cobalt (Co) in this case.

Inside the complex ion [Co(NH₃)₅Cl]²⁺:

• There are 5 neutral ammonia (NH₃) ligands → charge = 0

• There is 1 chloride (Cl⁻) ligand → charge = -1

• The overall charge on the complex ion is +2

Let the oxidation state of cobalt be x.

Now apply the formula:
x + (5 × 0) + (-1) = +2
x - 1 = +2
x = +3

Therefore, the oxidation state of cobalt is +3, which is also its primary valence.

Outside the coordination sphere, there are two chloride ions (Cl⁻) that balance the +2 charge of the complex ion.

Concept:

The standard potential E⁰ of a galvanic cell is referred to as the sum of the standard half cell potential for the oxidation and reduction half cells.

E⁰_cell = E⁰ _reduced - E⁰_oxidised

Explanation:

For the cell,

Zn | Zn2+ (IM) || I- (IM) | CuI | Cu

Zn (s) Zn²⁺ (aq) + 2e^- ⇒ E⁰_ox = - 0.76V
Cu²⁺ (aq) + 2e- → Cu (s) ⇒ E⁰_red = - 0.17V

The overall reaction is,
Zn(s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu (s)
The standard potential E° of the cell,

E⁰_cell = E⁰ _copper -  E⁰ _zinc
E⁰_cell = -0.17 - (-0.76) = -0.17 + 0.76 = 0.59 V

Concept:

• The order of a reaction is the summation of the powers of all the reactants which is expressed in the rate law.
• The order of reaction can be 0,1,2, etc, and even fractional.
• Zero order reaction is the reaction, where the rate of the reaction is proportional to the reactant to the power zero.
• rate [A]⁰
• The half-life refers to the time taken to reach its half concentration.
• The mathematical relationship is as follows,
• t 1/2 = [A₀]/2K
• Where A₀ is the initial concentration of the reactant and K is the rate constant.

Explanation:

From question,

The half-life of zero order is

t 1/2 = [A₀]/2K

 t 1/2will be doubled on doubling the initial concentration.

Hence, the correct option for the given question is, 2) Is doubled.

Activation energy-

• Activation energy is defined as the minimum amount of extra energy required by a reacting molecule to get converted into a product.
• It can also be described as the minimum amount of energy needed to activate or energize molecules or atoms so that they can undergo a chemical reaction or transformation.

Endothermic reaction-

• Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.
• These reactions lower the temperature of their surrounding area, thereby creating a cooling effect. Physical processes can be endothermic as well – Ice cubes absorb heat energy from their surroundings and melt to form liquid water (no chemical bonds are broken or formed).

Given data and Calculation:
⇒ An endothermic reaction A → B has an activation energy of 15 kcal/mole and energy of reaction of 5 kcal/mole
⇒ For an endothermic reaction, the activation energy for the backward reaction is equal to the difference between the activation energy of the forward reaction and the enthalpy change of the reaction.

Thus, the activation energy of the reaction B → A is 15 − 5 = 10 kcal/mole

Concept:

Kohlrausch law of independent migration of ions :

→ The law states that limiting the molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte.

→ Thus, if λ ° Na ⁺ and λ ° Cl ^– are limiting molar conductivity of the sodium and chloride ions respectively, then the limiting molar conductivity for sodium chloride is given by the equation:

→ Λ ° _m (NaCl) = λ ° Na ⁺ + λ ° Cl ^–

Calculation:

Given,

Molar conductance of NaCl, HCl, and CH3COONa at infinite dilution are 126.45, 426.16, and 91.0 S cm² mol−1

According to Kohlrausch's law of independent migration of ions.

Λ^∘_m (CH₃COOH)

Λ^∘_M (CH3 COONa) + Λ^∘_M (HCL) Λ^∘_M (NaCL)

= 91.0 S cm² mol-1 + 426.16 S cm² mol-1 - 126.45 S cm² mol-1

= 390.71 S cm² mol-1

The correct answer is Ammonium chloride and zinc chloride.
CONCEPT:

• The dry cell is a type of battery used in electric devices.
• As it uses electrolyte in the form of a paste, it can be used in portable devices.
• The dry cell consists of a Zinc container which also acts as the anode and carbon (graphite) rod acts as the cathode surrounded by powdered Manganese dioxide, carbon and electrolyte ammonium chloride in the form of a paste.
• Electrode reactions are :

At anode : Zn(s) → Zn²⁺ + 2e–

At cathode : MnO₂ + NH₄ ⁺ + e¯ → MnO(OH) + NH₃
EXPLANATION:

• In a dry cell ammonium chloride and zinc chloride is used in the form of electrolytes
• Ammonium chloride is mixed with Plaster of Paris to form a paste, with a small amount of zinc chloride added to increase the shelf life of the battery
• Ammonium chloride paste allows current to flow.
• Zinc chloride paste allows a dry-cell to conduct the electricity and provide electrical power to various substances.

Adding a non-volatile solute decreases the number of solvent molecules in the vapor phase, lowering the vapor pressure.

According to Raoult’s Law, the vapor pressure of the solvent is directly proportional to the mole fraction of the solvent in the solution. It is given by:

P = P_∘⋅X_solvent

where P^∘  is the vapor pressure of the pure solvent and X_solvent is the mole fraction of the solvent. Thus, the vapor pressure is directly proportional to the mole fraction of the solven

As NaCl is added to water, the vapor pressure of the solution decreases due to the presence of solute molecules.

Raoult's Law describes the lowering of the vapor pressure of a solvent in a solution due to the addition of a non-volatile solute. It states that the vapor pressure of the solvent is proportional to its mole fraction in the solution.

As the concentration of NaCl increases, the mole fraction of water (the solvent) decreases. According to Raoult's Law, this leads to a greater reduction in the vapor pressure of the solution.

(A) is correct: Werner’s theory proposed the concept of primary and secondary valences for coordination compounds.
(B) is correct: Homoleptic complexes contain ligands that are all of the same type.
(C) is correct: The coordination number is determined by the number of sigma bonds between the metal and the ligands.
(D) is correct: In an octahedral complex, the splitting of d orbitals results in t2g orbitals having lower energy than eg orbitals.

(A) is correct: Δo is influenced by the ligand field strength, which depends on the nature of the ligands.
(B) is incorrect: The coordination number refers to the number of bonds, not the number of ligands.
(C) is incorrect: Tetrahedral complexes usually exhibit high-spin behavior, not low-spin.
(D) is correct: Heteroleptic complexes contain different types of ligands.

(A) is incorrect: The bond between the metal and the ligand is often covalent, not purely ionic.
(B) is correct: The coordination number varies based on the ligand size and bonding characteristics.
(C) is correct: Coordination compounds can exhibit geometrical isomerism, especially in octahedral and square planar complexes.
(D) is incorrect: The bond is not always ionic; it can be covalent in nature.

A salt bridge is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.

Electrode potential is the tendency of an electrode to accept or to lose electrons. Electrode potential depends on the nature of the electrode, temperature of the solution and the concentration of metal ions in the solution. It doesn’t depend on the size of the electrode.

When solute molecules associate in solution (e.g., benzoic acid in benzene), the number of particles decreases. Colligative properties, which are proportional to the number of particles, are reduced. The observed molar mass, inversely proportional to colligative properties, is higher than the theoretical molar mass (assuming no association). Thus, (B) is correct.

Only sodium chloride has vant hoff factor greater than 1 (which is 2) in water

(B, C, D) Benzoic acid, acetic acid, and phenol in benzene associate (e.g., form dimers), reducing the number of particles, so i<1.

Given,
Depression in freezing point(ΔT) = -0.2 °C
Molality of the solution(m) = 0.1 m
Freezing point depression constant (Kf) = 4.0 °C m^-1
Let the Van’t Hoff factor = i
We know that, ΔT = i x K_f x m
0.2 = i x 4 x 0.1
i = 0.2/0.4 = 0.5
Therefore, the ratio between the normal mass and abnormal mass, which is equal to the Van’t Hoff factor is equal to 0.5.

KOH→K⁺ + OH^–
(NH₄)₂SO₄→2NH₄⁺ + SO4^2-
K₂CO₃→2K⁺ + CO₃^2-
K₂SO₄→2K⁺ + SO₄^2-
Concentration of particles in 1.0 M KOH solution is minimum (= 2 M). Hence, it will have minimum elevation in boiling point.

Given,
Degree of association (α) = 50% = 0.5
Number of molecules associated (n) = 2
Let the Van’t Hoff factor = i
We know that for solutes that associate in solution, i = 1 + ((1/n) -1) x α
= 1 + ((1/2) – 1) x 0.5
= 1 – (0.5 x 0.5)
= 0.75
Therefore, the Van’t Hoff factor is equal to 0.75.

Van’t Hoff Factor can also be written as the ratio between the total number of moles of particles after association / dissociation and the total number of moles of particles before association / dissociation. Since BaCl₂ completely dissociates(into one Ba2⁺ and two Cl^- ions), the total number of moles after dissociation is equal to 3. Therefore, the Van’t Hoff Factor for BaCl₂ is 3.

Van’t Hoff’s factor (i) is defined as the ratio of the observed colligative property to the calculated colligative property. Since, the abnormal mass for solutes that dissociate is lesser than its normal molar mass, the value of Van’t Hoff’s factor will always be > 1.

Solubility is the maximum concentration of solute that can dissolve in a solvent at a specific temperature and pressure, typically expressed as grams of solute per 100 grams of solvent. Beyond this limit, additional solute does not dissolve and may precipitate. (Supersaturated solutions occur under specific conditions, such as cooling a saturated solution without crystallization.)

CO₂ obeys Henry’s law, which governs the solubility of gases in liquids in relation to its pressure. Henry’s law states that mole fraction of gas in the solution varies directly with its partial pressure over the surface i.e. p ∝ x (mole fraction). The graph is of the form y = mx, a positively sloped straight line passing through the origin.