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Question 251

AIIMS BSc Nursing 2023• Chemistry

Galvanic cell is also known as

  1. AOption (a)

    mercury cell

  2. BOption (b)

    voltaic cell 

  3. COption (c)

    leclanche cell

  4. DOption (d)

    secondary cell

View answer & explanation

Correct answer

Answer: (b)B.

voltaic cell 

Why this answer is correct

CONCEPT:

Galvanic Cell

  • A galvanic cell, also known as a voltaic cell, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell.
  • In a galvanic cell, chemical energy is converted into electrical energy.

EXPLANATION:​

  • The correct name for a galvanic cell is a voltaic cell.
  • Mercury cell is a type of primary cell that uses mercury oxide as the cathode.
  • Leclanche cell is a type of primary cell commonly used in batteries.
  • Secondary cell refers to rechargeable batteries.

Therefore, the correct answer is Option 2: Voltaic cell.

Question 252

AIIMS BSc Nursing 2023• Chemistry

Write the type of reaction involved in the following chemical equation.

TiCl4 + Mg → Ti + MgCl4

  1. AOption (a)

    Combination reaction

  2. BOption (b)

    Displacement reaction 

  3. COption (c)

    Decomposition reaction

  4. DOption (d)

    Disproportionation reaction

View answer & explanation

Correct answer

Answer: (b)B.

Displacement reaction 

Why this answer is correct

CONCEPT:

Displacement Reaction

  • A displacement reaction occurs when an element reacts with a compound and takes the place of another element in that compound.
  • In a displacement reaction, a more reactive element displaces a less reactive element from its compound.

EXPLANATION:

  • In the given reaction:

TiCl4 + Mg → Ti + MgCl2

  • Magnesium (Mg) is more reactive than titanium (Ti).
  • Magnesium displaces titanium from titanium tetrachloride (TiCl4).
  • This means that magnesium takes the place of titanium in the compound, forming magnesium chloride (MgCl2) and releasing titanium.

Therefore, the type of reaction involved in the given chemical equation is a displacement reaction.

Question 253

AIIMS BSc Nursing 2023• Chemistry

In which defect equal number of cations and anions are missing from their lattice position?

  1. AOption (a)

    Schottky defect

  2. BOption (b)

    Vacancy defect

  3. COption (c)

    Impurity defect

  4. DOption (d)

    Frenkel defect

View answer & explanation

Correct answer

Answer: (a)A.

Schottky defect

Why this answer is correct

CONCEPT:

Schottky defect:

  • Schottky defect is a type of point defect or imperfection in solids which is caused by a vacant position that is generated in a crystal lattice due to the atoms or ions moving out from the interior to the surface of the crystal.
  • Schottky defect in crystals is observed when equal numbers of cations and anions are missing from the lattice.
  • It is important that an equal number of cations and anions are missing, otherwise, the electrical neutrality of the crystal will get affected.

Additional Information

Defects/ ImperfectionsTypes of Defects / Imperfection
Point defects (Zero-dimensional)Vacancy Defect: It appears due to the missing of an atom from the lattice. Frenkel defect: Atom occupies interstitial void in the lattice. Schottky defect: It appears if, in a combination of cation and anion there is a vacancy. Interstitial defect: It appears when a foreign atom occupies the interstitial site Substitutional defect: It appears if a regular atom is replaced by another foreign atom.
Line defect or dislocations (One-Dimensional)Edge dislocation: If force is applied on 50% area and exceeds beyond a certain limit slipping of plane happens and an extra half-plane appears at dislocation line. Screw dislocation: Formed by the shear stress that is applied to produce the distortion.
Surface defects (Two-Dimensional)Grain boundary defect: Due to the orientation mismatch at the grain boundary the bond length is more and can be easily broken. Tilt boundary defect: When the orientation mismatch at the grain boundary is 0.5° - 1° then grain boundaries are called tilt boundaries.

Therefore, in Schottky defect, equal numbers of cations and anions are missing from their lattice positions.

Question 254

AIIMS BSc Nursing 2023• Chemistry

Write the chemical formula for Iron (III) hexacyanoferrate (II) is

  1. AOption (a)

    Fe4(Fe(CN)6]3

  2. BOption (b)

    Fe[Fe(CN)6]

  3. COption (c)

    Fe3[Fe(CN)6]

  4. DOption (d)

    Fe[Fe(CN)6]5

View answer & explanation

Correct answer

Answer: (a)A.

Fe4(Fe(CN)6]3

Why this answer is correct

CONCEPT:

Coordination Compounds and Complex Ions

  • Coordination compounds consist of a central metal atom or ion bonded to surrounding ligands (molecules or ions).
  • The formula of a coordination compound is written as [Metal(Ligand)n].
  • The oxidation state of the metal ion is indicated in Roman numerals in parentheses.

EXPLANATION:

  • In the given complex, Iron (III) hexacyanoferrate (II):
  • Iron (III) indicates that the central iron ion has an oxidation state of +3.
  • Hexacyanoferrate (II) indicates that the hexacyanoferrate ion has an iron ion with an oxidation state of +2 and is coordinated with six cyanide (CN-) ligands.
  • The hexacyanoferrate (II) ion is [Fe(CN)6]4-, because each CN has a -1 charge and there are 6 of them, making the total charge of the ion -4.
  • To balance the charges, three Fe3+ ions are needed to neutralize the charge of four [Fe(CN)6]4- ions.

Therefore, the chemical formula for Iron (III) hexacyanoferrate (II) is Fe4[Fe(CN)6]3.

Question 255

AIIMS BSc Nursing 2023• Chemistry

What is the similarity between diamond and graphite. 

  1. AOption (a)

    Both are soft

  2. BOption (b)

    Both are conductors

  3. COption (c)

    Both are insulators

  4. DOption (d)

    Both are covalent or network solids

View answer & explanation

Correct answer

Answer: (d)D.

Both are covalent or network solids

Why this answer is correct

CONCEPT:

Diamond and Graphite

  • Diamond and graphite are both allotropes of carbon, meaning they are different structural forms of the same element, carbon.
  • Both diamond and graphite consist of carbon atoms, but they have different arrangements and bonding structures.
  • Diamond has a tetrahedral structure where each carbon atom is bonded to four other carbon atoms in a three-dimensional network.
  • Graphite has a planar hexagonal structure where each carbon atom is bonded to three other carbon atoms, forming layers that can slide over each other.

EXPLANATION:

  • The similarity between diamond and graphite:
  • Both diamond and graphite are covalent or network solids.
  • This means that they are composed of a continuous network of covalent bonds extending throughout the material.
  • While their physical properties differ significantly (diamond is hard and an insulator, whereas graphite is soft and a conductor), the fundamental similarity lies in their bonding and structure as covalent network solids.

Therefore, the correct option is 4) Both are covalent or network solids.

Question 256

AIIMS BSc Nursing 2023• Chemistry

The correct order of configuration of O2 molecule according to MOT is

  1. AOption (a)

    \(\begin{array}{l} \sigma \mathrm{s}^{2}<\sigma^{} 1 \mathrm{~s}^{2}<\sigma 2 \mathrm{~s}^{2}<\sigma^{} 2 \mathrm{~s}^{2}<\left(\pi 2 \mathrm{p}{\mathrm{x}}^{2}=\pi 2 \mathrm{p}{\mathrm{y}}^{2}\right) <\sigma 2 \mathrm{p}{\mathrm{z}}^{2}<\left(\pi^{*} 2 \mathrm{p}{\mathrm{x}}^{1}=\pi^{*} 2 \mathrm{p}_{\mathrm{y}}^{1}\right) \end{array}\)

  2. BOption (b)

    \(\begin{array}{l} \sigma 1 s^{2}<\sigma^{} 1 s^{2}<\sigma 2 s^{2}<\sigma * 2 s^{2}<\sigma 2 p_{z}^{2}< \left(\pi 2 p_{x}^{2}=\pi 2 \mathrm{p}_{\mathrm{y}}^{2}\right)<\left(\pi^{} 2 \mathrm{p}{\mathrm{x}}^{1}=\pi^{*} 2 \mathrm{p}{\mathrm{y}}^{1}\right) \end{array}\)

  3. COption (c)

    \(\begin{array}{l} \sigma 1 s^{2}<\sigma^{} 1 s^{2}<\sigma 2 s^{2}<\left(\pi 2 p^{2}=\pi 2 p_{y}^{2}\right) <\left(\pi^{} 2 p_{x}^{2}=\pi^{} 2 p_{y}^{2}\right)<\sigma^{} 2 s^{2} \end{array}\)

  4. DOption (d)

    \(\begin{array}{l} \sigma 1 s^{2}<\sigma * 1 s^{2}<\sigma 2 s^{2}<\sigma * 2 s^{2}<\left(\pi 2 p_{x}^{2}=\pi 2 p_{y}^{2}\right) <\left(\pi^{} 2 p_{x}^{2}=\pi^{} 2 p_{y}^{2}\right) \end{array}\)

View answer & explanation

Correct answer

Answer: (b)B.

\(\begin{array}{l} \sigma 1 s^{2}<\sigma^{} 1 s^{2}<\sigma 2 s^{2}<\sigma * 2 s^{2}<\sigma 2 p_{z}^{2}< \left(\pi 2 p_{x}^{2}=\pi 2 \mathrm{p}_{\mathrm{y}}^{2}\right)<\left(\pi^{} 2 \mathrm{p}{\mathrm{x}}^{1}=\pi^{*} 2 \mathrm{p}{\mathrm{y}}^{1}\right) \end{array}\)

Why this answer is correct

CONCEPT:

Molecular Orbital Theory (MOT) for O2 Molecule

  • Molecular Orbital Theory (MOT) explains the bonding in molecules by combining atomic orbitals to form molecular orbitals, which are spread over the entire molecule.
  • In O2, the molecular orbitals are formed by the combination of atomic orbitals from two oxygen atoms.
  • The molecular orbitals are filled according to the Aufbau principle, Pauli exclusion principle, and Hund's rule.

EXPLANATION:

  • The correct order of filling molecular orbitals for O2 molecule is as follows:
  • σ 1s2: The bonding molecular orbital formed by the combination of 1s orbitals from both oxygen atoms.
  • *σ 1s2**: The antibonding molecular orbital formed by the combination of 1s orbitals from both oxygen atoms.
  • σ 2s2: The bonding molecular orbital formed by the combination of 2s orbitals from both oxygen atoms.
  • *σ 2s2**: The antibonding molecular orbital formed by the combination of 2s orbitals from both oxygen atoms.
  • σ 2pz2: The bonding molecular orbital formed by the combination of 2pz orbitals from both oxygen atoms.
  • π 2px2 = π 2py2: The degenerate bonding molecular orbitals formed by the combination of 2px and 2py orbitals from both oxygen atoms.
  • π 2px1 = π 2py1**: The degenerate antibonding molecular orbitals formed by the combination of 2px and 2py orbitals from both oxygen atoms.
  • Based on this order, the correct configuration of the O2 molecule is:

σ 1s2 < σ* 1s2 < σ 2s2 < σ* 2s2 < σ 2pz2 < (π 2px2 = π 2py2) < (π* 2px1 = π* 2py1)

Therefore, the correct order of configuration of O2 molecule according to MOT is Option 2.

Question 257

AIIMS BSc Nursing 2023• Chemistry

In which type of system, exchange of energy is possible but not exchange of matter?

  1. AOption (a)

    Open system

  2. BOption (b)

    Isolated system

  3. COption (c)

    Closed system

  4. DOption (d)

    Adiabatic system

View answer & explanation

Correct answer

Answer: (c)C.

Closed system

Why this answer is correct

CONCEPT:

Types of Systems in Thermodynamics

  • In thermodynamics, systems are classified based on the exchange of energy and matter with their surroundings.
  • There are three main types of systems:
  • Open System: Both energy and matter can be exchanged with the surroundings.
  • Isolated System: Neither energy nor matter can be exchanged with the surroundings.
  • Closed System: Only energy can be exchanged with the surroundings, but not matter.
  • Adiabatic System: No heat exchange occurs with the surroundings, but work and matter can be exchanged in some contexts.

EXPLANATION:

  • Based on the definitions of the different types of systems:
  • An Open System allows both energy and matter to be exchanged.
  • An Isolated System does not allow either energy or matter to be exchanged.
  • A Closed System allows the exchange of energy but not matter.
  • An Adiabatic System does not allow heat exchange but may allow other forms of energy and matter to be exchanged.
  • The correct answer is a Closed System.

Therefore, the correct answer is Option 3: Closed system.

Question 258

AIIMS BSc Nursing 2023• Chemistry

Arrange the following elements in decreasing order of their atomic size.

W, Re, Ir, Os

  1. AOption (a)

    W > Re > Ir > Os

  2. BOption (b)

    W > Re > Os > Ir 

  3. COption (c)

    W > Ir > Os > Re

  4. DOption (d)

    Re > W > Os > Ir

View answer & explanation

Correct answer

Answer: (b)B.

W > Re > Os > Ir 

Why this answer is correct

CONCEPT:

Atomic Size

  • The atomic size of an element is determined by the distance from the nucleus to the outermost electron cloud.
  • Within a group in the periodic table, atomic size increases as you move down because additional electron shells are added.
  • Within a period, atomic size decreases from left to right due to the increasing nuclear charge, which pulls electrons closer to the nucleus.

EXPLANATION:

  • As we move across the period from left to right, the atomic size generally decreases.
  • Thus, the order of atomic size from largest to smallest among these elements is as follows:
  • Tungsten (W) is the largest because it is the furthest to the left.
  • Rhenium (Re) follows W.
  • Osmium (Os) comes after Re.
  • Iridium (Ir) is the smallest as it is the furthest to the right.

Therefore, the correct order of decreasing atomic size is: W > Re > Os > Ir.

Question 259

AIIMS BSc Nursing 2023• Chemistry

Which of the following is isoelectronic?

  1. AOption (a)

    CO2, NO2

  2. BOption (b)

    \(\mathrm{NO}{2}^{-}, \mathrm{CO}{2}\)

  3. COption (c)

    CN-, CO

  4. DOption (d)

    SO2, CO2

View answer & explanation

Correct answer

Answer: (c)C.

CN-, CO

Why this answer is correct

CONCEPT:

Isoelectronic Species

  • Isoelectronic species are atoms, ions, or molecules that have the same number of electrons.
  • To determine if species are isoelectronic, count the total number of electrons in each species and compare them.

EXPLANATION:

  • Calculate the number of electrons in each species:
  • CO2: C (6 electrons) + 2 * O (8 electrons each) = 6 + 16 = 22 electrons
  • NO2: N (7 electrons) + 2 * O (8 electrons each) = 7 + 16 = 23 electrons
  • NO2-: N (7 electrons) + 2 * O (8 electrons each) + 1 extra electron = 7 + 16 + 1 = 24 electrons
  • CN-: C (6 electrons) + N (7 electrons) + 1 extra electron = 6 + 7 + 1 = 14 electrons
  • CO: C (6 electrons) + O (8 electrons) = 6 + 8 = 14 electrons
  • SO2: S (16 electrons) + 2 * O (8 electrons each) = 16 + 16 = 32 electrons
  • Identify the isoelectronic pairs:
  • CN- (14 electrons) and CO (14 electrons) are isoelectronic.

Therefore, the correct answer is Option 3: CN- and CO.

Question 260

AIIMS BSc Nursing 2023• Chemistry

Bakelite is prepared by the reaction between 

  1. AOption (a)

    urea and formaldehyde

  2. BOption (b)

    ethylene glycol

  3. COption (c)

    phenol and formaldehyde

  4. DOption (d)

    tetramethylene glycol

View answer & explanation

Correct answer

Answer: (c)C.

phenol and formaldehyde

Why this answer is correct

CONCEPT:

Bakelite Preparation

  • Bakelite is a type of plastic, specifically a phenolic resin, that is created by the reaction of phenol with formaldehyde.
  • The reaction involves the formation of a complex network polymer through a condensation reaction.
  • This polymer is known for its high resistance to heat and chemicals, making it useful in electrical insulators and various other applications.

EXPLANATION:

  • In the given reaction for the preparation of Bakelite:

Phenol + Formaldehyde → Bakelite

  • Phenol acts as the primary reactant, providing the aromatic ring structure.
  • Formaldehyde acts as the linking agent, forming methylene bridges between the phenol units.
  • Among these options, the correct pair of reactants for the formation of Bakelite is:
  • Option 3: Phenol and formaldehyde

Therefore, Bakelite is prepared by the reaction between phenol and formaldehyde.

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