Chemistry (Theory) Official 2022-2023 ISC (Science) ISC Class 12 Question Paper Solution

Fill in the blanks by choosing the appropriate words from those given in the brackets:

[stable, low, aldehyde, unstable, 6, 4, ethane, Clemmensen’s, 2, 3, carboxylic acid, high, propane, Rosenmund's]

The primary alcohols are easily oxidised first into ______ and then into ______.

Fill in the blanks by choosing the appropriate words from those given in the brackets:

[stable, low, aldehyde, unstable, 6, 4, ethane, Clemmensen’s, 2, 3, carboxylic acid, high, propane, Rosenmund's]

The intermediate activated complex in a chemical reaction is highly ______ due to ______ energy.

Fill in the blanks by choosing the appropriate words from those given in the brackets:

[stable, low, aldehyde, unstable, 6, 4, ethane, Clemmensen’s, 2, 3, carboxylic acid, high, propane, Rosenmund's]

The coordination number and oxidation state of the complex K₄[Fe(CN₆)] are ______ and ______ respectively.

Propanone on reaction with zinc amalgam in the presence of conc. HCI gives ______ and the reaction is known as ______ reduction.

stable 

low

aldehyde

unstable

6

4

ethane

Clemmensen’s

2

3

carboxylic acid

high

propane

Rosenmund's

The reaction of a primary amine with chloroform and ethanolic KOH is called ______.

Carbylamine reaction

Kolbe's reaction

Reimer-Tiemann reaction

Wurtz-Fittig reaction

Which one of the following statements is true for the galvanic cell?

Electrons flow from the copper electrode to the zinc electrode.

Current flows from the zinc electrode to the copper electrode.

Cations move towards the copper electrode.

Cations move towards zinc electrode.

Which one of the following compounds is diamagnetic and colourless?

\[\ce{K2Cr2O7}\]

\[\ce{ZnSO4}\]

\[\ce{KMnO4}\]

\[\ce{Cr2(SO4)3}\]

For a first order reaction, the half-life period (t_1/2) is ______.

proportional to the initial concentration.

inversely proportional to the initial concentration.

proportional to the square root of the initial concentration.

independent of the initial concentration.

Match the following:

Assertion: If a solution contains both H⁺ and Na⁺ ions, the H⁺ ions are reduced first at cathode.

Reason: Cations with higher E° value are reduced first at cathode.

Both Assertion and reason are true and Reason is the correct explanation for Assertion.

Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion.

Assertion is true but Reason is false.

Assertion is false but Reason is true.

Assertion: Addition of bromine water to 1-butene gives two optical isomers.

Reason: The product formed contains two asymmetric carbon atoms.

Both Assertion and Reason are true, and Reason is the correct explanation for Assertion.

Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion.

Assertion is true but Reason is false.

Assertion is false, but Reason is true.

Calculate the mass of ascorbic acid (molecular mass = 176 g/mol) that should be dissolved in 155 g of acetic acid to cause a depression of the freezing point by 1.15 K. Assume that ascorbic acid does not dissociate or associate in the solution. (K_f for acetic acid = 3.9 K kg/mol)

Give a reason for the following:

Cu⁺² salts are paramagnetic, while Cu⁺ salts are diamagnetic.

Give a reason for the following:

Mn⁺² compounds are more stable than Fe⁺² compounds.

Give a chemical equation for the following:

Ethyl chloride is treated with aqueous KOH solution.

Give a chemical equation for the following:

Chlorobenzene is treated with ammonia at 573 K and high pressure.

State one reason for the following:

Alkylamine is soluble in water, whereas arylamine is insoluble in water.

State one reason for the following:

Methylamine is a stronger base than methyl alcohol.

Calculate the emf of the following cell at 298 K.

\[\ce{Cu/Cu^{2+}_{(0.025 M)}//Ag^+_{(0.005 M)}/Ag}\]

Given `"E"_("Cu"^(2+)//"Cu")^circ` = 0.34 V, `"E"_("Ag"^+//"Ag")^circ` = 0.80 V

1 Faraday = 96500 C mol ^-1

Complete and balance the following chemical equation:

\[\ce{KMnO4 + KI + H2SO4 ->}\] _____ + _____ + _____ + ______

Complete and balance the following chemical equation:

\[\ce{K2Cr2O7 + H2SO4 + H2S ->}\] ______ + ______ + ______ + ______

How will the following be obtained? (Give chemical equation):

Ethanol from Grignard's reagent.

How will the following be obtained? (Give chemical equation):

Diethyl ether from sodium ethoxide.

An organic compound [A] C₂H₆O, on heating with conc. H₂SO₄ at 413 K gives a neutral compound [B] C₄H₁₀O. Compound [B] on treatment with PCl₅ gives a product, which on subsequent treatment with KCN yields compound [C] C₃H₅N. Compound [C] on hydrolysis gives an acid [D] C₃H₆O₂. Identify the compounds [A], [B], [C] and [D].

The osmotic pressure of blood at 37°C is 8.21 atm. How much glucose in grams should be used per litre of aqueous solution for an intravenous injection so that it is isotonic with blood? (Molecular wt of glucose = 180 g/mol)

An aromatic carboxylic acid [A], which readily sublimes on heating, produces compound [B] on treatment with PCl₅, Compound [B], when reduced in the presence of Pd catalyst over BaSO₄ poisoned by sulphur in xylene solution, gives compound [C]. When compound [C] is condensed in the presence of alcoholic KCN, it gives compound [D] (Molecular formula of compound [D] is C₁₄H₁₂O₂)

Identify the compounds [A], [B], [C] and [D].

State a reason for the following:

La(OH)₃ is more basic than Lu(OH)₃.

How would you account for the following? 

Transition metals and their compounds act as catalysts.

20% of a first-order reaction is completed in five minutes. How much time will the 60% reaction take to complete? Calculate the half-life period (t_1/2) for the above reaction.

Write the balanced chemical equation for the following name reaction:

Sandmeyer's reaction

Write the balanced chemical equation for the following name reaction:

Wurtz reaction

Write the balanced chemical equation for the following name reaction:

Finkelstein reaction

Give an example of reducing sugar.

Give an example of non-reducing sugar.

What is denaturation of proteins?

Give an example of water soluble vitamin.

Give an example of fat soluble vitamin.

When 2 g of benzoic acid is dissolved in 25 g of benzene, it shows a depression in freezing point equal to 1.62 K. The molal depression constant (K_f) of benzene is 4.9 K kg mol⁻¹, and the molecular weight of benzoic acid is 122 g/mol. What will be the percentage association of the benzoic acid?

(Benzoic acid forms dimers when dissolved in benzene.)

Account for the following:

Phenol is a stronger acid than aliphatic alcohol.

Account for the following:

Ethanol gives iodoform reaction whereas methanol does not give iodoform reaction.

Account for the following:

Ethers should not be distilled to dryness.

Identify the compounds [A], [B] and [C] in the following reaction:

\[\ce{CH3COOH ->[NH3][\Delta] [A] ->[Br2 + KOH] [B] ->[CHCl3 + NaOH_{(alc)}] [C]}\]

Identify the compounds [A], [B] and [C] in the following reaction:

\[\ce{CH3Br ->[KCN] [A] ->[LiAlH_4] [B] ->[HNO2][273 K] [C]}\]

How will the following be converted? (Give chemical equation)

Ethyl bromide to ethyl isocyanide

How will the following be converted? (Give chemical equation)

Aniline to benzene diazonium chloride.

How will the following be converted? (Give chemical equation)

Benzene diazonium chloride to phenol

A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction. (Given : log 2 = 0·3010, log 4 = 0·6021, R = 8·314 JK^–1 mol^–1)

Write a chemical equation to illustrate the following name reaction:

Cannizzaro’s reaction.

Write a chemical equation to illustrate the following name reaction:

HVZ reaction

Write a chemical equation to illustrate the following name reaction:

Aldol condensation.

How will the following be converted? (Give chemical equation)

Acetaldehyde to acetone

How will you bring about the following conversion? (Give equation).

Formaldehyde to urotropine.

Name the type of isomerism exhibited by the following pair of compounds:

[Co(NH₃)₅(ONO)]Cl₂ and [Co(NH₃)₅(NO₂)]Cl₂

Name the type of isomerism exhibited by the following pair of compounds:

[Cr(H₂O)₅Cl]Cl₂.H₂O and [Cr(H₂O)₄Cl₂]Cl.2H₂O

Name the type of isomerism exhibited by the following pair of compound:

\[\ce{[Pt(NH3)4Cl2]Br2  and  [Pt(NH3)4 Br2]Cl2}\]

Write the IUPAC name of the following complex:

\[\ce{[Co(NH3)4(H2O)2]Cl3}\]

Write the IUPAC name of the following complex:

\[\ce{K2[Ni(CN4)]}\]

The specific conductance of 2.5 × 10^-4 M formic acid is 5.25 × 10^-5 ohm^-1 cm^-1. Calculate its molar conductivity and degree of dissociation.

Given `λ°_("H"^+)` = 349.5 ohm^-1 cm² mol^-1 and

`λ°_("HCOO"^-)  = 50.5 " ohm"^-1 "cm"^2  "mol"^-1`

Calculate the time taken to deposit 1.27 g at copper at cathode when a current of 2 amp. is passed through the solution of CuSO₄.

(Atomic weight of Cu = 63.5 gmol^-1)

The resistance of a conductivity cell with a 0.1 M KCl solution is 200 ohm. When the same cell is filled with a 0.02 M NaCl solution, the resistance is 1100 ohm. If the conductivity of 0.1 M KCl solution is 0.0129 ohm^-1 cm^-1, calculate the cell constant and molar conductivity of 0.02 M NaCl solution.

The emf \[\ce{E^\circ_\text{cell}}\] of the following reaction is 0.89 V.

\[\ce{3Sn^{4+} + 2Cr -> 3Sn^{2+} + 2Cr^{1+}}\]

Calculate the value of ΔG° for the reaction. Predict whether the above reaction will be spontaneous or not.