Chemistry (Theory) Official Board 2024-2025 ISC (Science) ISC Class 12 Question Paper Solution

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]

______ is an example of a primary cell but ______ is an example of a secondary cell.

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]

The complex compound [Ni(CO)₄] is ______ in shape and nickel is in ______ oxidation state in this complex compound.

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]

When acetaldehyde is treated with hydrazine and KOH in a high boiling solvent glycol, ______ is formed and the reaction is known as ______ reduction.

Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:

[+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]

The transition metal ions having ______ d-orbitals are colourless and ______ in nature.

Which one of the following can produce the foul smelling compound methyl isocyanide in presence of alcoholic KOH?

Chloroform and aniline

Chloroform and methanol

Chloroform and dimethyl amine

Chloroform and methyl amine

The osmotic pressure of a solution:

(P) increases with an increase in number of moles of solute.

(Q) decreases with an increase in number of moles of solute.

(R) increases at a higher temperature.

(S) is dependent on the nature of solute.

Which one of the following is correct?

Only (P) and (Q) are correct.

Only (P) and (R) are correct.

Only (P) and (S) are correct.

Only (Q) and (S) are correct.

Which one of the following alcohols is the strongest acid?

Phenol

Methanol

Ethanol

t-butyl alcohol

Which one of the following does NOT form a silver mirror on heating with Tollen’s reagent?

Glucose

Fructose

Sucrose

Lactose

The coordination number and the oxidation state of the central metal ‘D’ in the complex [D(en)₂(H₂O)₂]Cl₃ are ______.

6 and 2 respectively

4 and 2 respectively

3 and 6 respectively

6 and 3 respectively

Assertion: The process of halogenation of benzene takes place in the presence of anhydrous FeCl₃.

Reason: Anhydrous FeCl₃ prepares nucleophile to attack the benzene ring.

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 and Reason is false.

Both Assertion and Reason are false.

Assertion: The Zr-Hf pair of elements has the same value of atomic radii though Zr and Hf are placed in different periods in the periodic table.

Reason: The lanthanoid contraction prevents the expected increase in atomic radii of Hf.

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 and Reason is false.

Both Assertion and Reason are false.

Read the passage carefully and answer the questions that follow.

1. What will be the order of reaction if the unit of k is mol⁻² L² s⁻¹?
2. State any one difference between order of reaction and molecularity of reaction.
3. For the reaction \[\ce{2A -> B + C}\], the rate law is rate = k[A]^3/2. What is the order and molecularity of the reaction?

Calculate the number of coulombs required to electroplate 4.75 g of aluminium when electrode reaction is \[\ce{Al^{3+} + 3e- -> Al}\].

(Given: Atomic weight of Al = 27 g mol⁻¹, 1 Faraday = 96,500 coulombs)

An organic compound [A] has molecular formula C₇H₆O₂. When compound [A] is treated with SOCl₂, it yields compound [B]. On heating with NH₃, compound [B] forms compound [C]. Compound [C] forms compound [D] on reaction with Br₂/KOH. Compound [D] responds to carbylamine test.

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

In the reaction \[\ce{2NO + O2 -> 2NO2}\], the rate law is rate = k[NO][O₂]².

1. How will the rate of reaction change if [NO] concentration is doubled and [O₂] concentration is halved at the same time?
2. Write the order of reaction if [NO] concentration is in large excess.

When an organic compound [A] having molecular formula C₄H₉Br is treated with aqueous KOH, the rate of reaction depends on concentration of compound [A] only. But when compound [B], with the same molecular formula, reacts with aqueous KOH, the rate of reaction depends on the concentration of compound [B] as well as of KOH. Compound [B] is a structural isomer of compound [A]. 

Identify compounds [A] and [B].

Write a balanced chemical equation for the following:

Ethyl cyanide is reduced with LiAlH₄.

Give balanced equation for the following:

Aniline is treated with bromine water. 

While conducting an experiment on coordination compounds, Shirin observed a white precipitate when AgNO₃ solution was added to the aqueous solution of the complex [Co(NH₃)₃(en)SO₄]Cl.

How can the ionisation isomer of this complex be detected by a chemical test? Write the structure and the IUPAC name of the ionisation isomer.

Arrange the following in the increasing order of their acidic strength:

CH₃CH₂OH, CF₃CH₂OH, CCl₃CH₂OH

Arrange the following in the increasing order of their boiling points:

CH₃CH₂OH, \[\begin{array}{cc}
\ce{CH2OH}\\
|\phantom{..........}\\
\ce{CH2OH}\\
\end{array}\], CH₃CH₂Cl

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

\[\ce{CH3COOH + PCl5 -> [A] ->[H2][\underset{Boiling Xylene}{Pd/BaSO4}] [B] ->[K2Cr2O7 + H2SO4][{[O]}] [C] ->[Ca(OH)2, heat] [D]}\]

Write a chemical equation to convert the following:

Benzaldehyde to benzene.

Convert the following:

Benzoic acid to Benzaldehyde.

Calculate the \[\ce{E^{\circ}_{cell}}\] of the following if the cell potential (E_cell) is 0.59 V.

(Given: Ni/Ni²⁺(0.1M)||Cu²⁺(0.01M)/Cu)

Write the chemical test to distinguish between the following pair of compounds.

Ethanol and propan-1-al

Write chemical test to distinguish between the following compounds:

Phenol and Benzoic acid

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

\[\ce{C2H5Br ->[KCN] [A] ->[LiAlH4][{[4H]}] [B] ->[HNO2][0^\circ-5^\circ C] [C]}\]

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

\[\ce{C2H5CONH2 ->[Br2/KOH] [A] ->[CHCl3 + KOH] [B] ->[Na/C2H5OH] [C]}\]

The scientist van’t Hoff introduced a factor (i) to account for the extent of association or dissociation of solutes. It is mathematically expressed as:

i = `"normal molecular mass"/"experimental molecular mass"`

In case of association, i < 1 and in case of dissociation i > 1.

1. In the calculation of molecular mass of K₄[Fe(CN)₆] by using a colligative property, what will be the value of van’t Hoff factor if the solute is 25% dissociated?
2. Find the value of van’t Hoff factor for a dilute aqueous solution of benzoic acid in water when it is completely associated to form a dimer.

Write a chemical equation to illustrate the following name reaction:

Finkelstein reaction

Write a chemical equation to illustrate the following name reaction:

Williamson’s synthesis

Write the equation involved in the following reaction:

Reimer-Tiemann reaction

According to Crystal-Field Theory, the electronic configuration of complex compound [A] is \[\ce{t^4_{2g}e^2_g}\] and that of complex compound [B] is \[\ce{t^6_{2g}e^0_g}\].

1. Which of the two complex compounds, [A] or [B], is a low spin complex?
2. Write the number of unpaired electrons in complex compounds [A] and [B].
3. Does complex [A] have strong field ligands or weak field ligands? Give a reason.

By referring to electrochemical series, how can anode and cathode half cells be identified in a galvanic cell?

What are the functions of a salt bridge in a galvanic cell?

Write two applications of fuel cells.

Write a disadvantage of a fuel cell.

Specific conductance of a solution decreases upon dilution. Why?

The emf of a cell should be positive for a spontaneous reaction. Give a reason.

Name the type of cell in which a reaction occurs only in one direction and cannot be reversed by an external energy source. Write any one disadvantage of this type of cell.

The structure of amino acid exists in the following two forms:

\[\begin{array}{cc}
\phantom{.........}\ce{O}\phantom{........................................}\ce{O}\phantom{.}\\
\phantom{.......}||\phantom{........................................}||\\
\ce{R - CH - C - OH <-->[aqueous] R - CH - C - O-}\\
|\phantom{..........................................}|\phantom{............}\\
\ce{NH2}\phantom{..................................}\ce{^+NH3}\phantom{........}\\
\end{array}\]

The above structure is an example of ______. If the side chain R is replaced by hydrogen, the amino acid is known as ______.

Janice notices that her gums bleed while brushing and eating food. Name the water soluble vitamin which she should consume to prevent bleeding of gums.

Which linkage holds two units of monosaccharides in a disaccharide?

The data given below is for the reaction between [NO] and [Cl₂] to form NOCl at 25°C.

Answer the following questions.

1. What is the order of reaction with regard to NO and Cl₂?
2. Calculate the overall order of the reaction.
3. Find the value of rate constant (k).

1. How is the acid mentioned above prepared from phenol? Write the chemical reaction involved in this preparation.
2. ‘Phenol is less soluble in water as compared to aliphatic alcohol.’ Explain.
3. Write the chemical equation for the preparation of phenol from chlorobenzene.
4. An organic compound [A] having molecular formula C₄H₁₀O gives positive Lucas test within five minutes at room temperature. Compound [A] upon oxidation with K₂Cr₂O₇/H₂SO₄ forms compound [B] which does not respond to Tollen’s test.
   Identify compounds [A] and [B].
5. In the above reaction, compound [B] gets reduced with Zn/Hg and HCl and forms compound [C]. Identify compound [C] and write the balanced reaction for the conversion of compound [B] to compound [C].

Give a reason for the following:

Ti³⁺ salts are coloured whereas Ti⁴⁺ salts are colourless. 

[Given: Atomic number of Ti = 22]

Give a reason for the following:

Transition elements form alloys.

Give a reason for the following:

The pink coloured KMnO₄ solution turns colourless when reacted with Mohr’s salt (Fe²⁺) in acidic medium.

Complete and balance the chemical equation:

\[\ce{KMnO4 + H2SO4 + H2C2O4 ->}\] ______ + ______ + ______ + ______

Complete and balance the following chemical equation:

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

Answer the questions below:

1. What will happen if red blood corpuscles are placed in a 5% NaCl solution which is a hypertonic solution?    [1]
2. Show that osmotic pressure (π) is a colligative property.    [1]
3. Calculate the amount of pressure required to stop osmosis of a solution when 40 g of Na₂SO₄ is added to 1 L of water at 298 K.
   (Given: Na = 23, O = 16, S = 32 and R = 0.0821 L atm K⁻¹ mol⁻¹)    [2]
4. Briefly discuss the process of reverse osmosis followed to desalinate sea water and convert it into drinking water.    [1]

An aqueous solution is made by dissolving 10 g of glucose (C₆H₁₂O₆) in 90 g of water at 300 K. If the vapour pressure of pure water at 300 K is 32.8 mm Hg, what would be the vapour pressure of the solution?

(Given: C = 12, H = 1 and O = 16)

A solution containing 12.5 g of a non-electrolyte solute in 175 g of water gave boiling point of 100.70°C. Calculate the molecular mass of the solute.

(Given: K_b for water = 0.52 K kg mol⁻¹)

Why are soda water bottles sealed under high pressure?