CBSE 2025, Set 3 Solutions
CBSE Chemistry (2025)

CH$_3$CH$_2$CHO and CH$_3$CH$_2$COOH can be distinguished by :

While doing qualitative analysis in chemistry lab, Abhishek added yellow coloured potassium chromate solution into a test tube. He was surprised to see the colour of the solution changing immediately to orange. He realised that the test tube was not clean and contained a few drops of some liquid. Which of the following substances will be the most likely liquid to be present in the test tube before adding potassium chromate solution?

The role of a catalyst is to change :

CH$_3$CH$_2$OH can be converted to CH$_3$CHO by :

The IUPAC name for CH$_3$–CH$_2$–N(CH$_3$)–CH$_2$–CH$_2$–CH$_3$ is :

A plot between concentration of reactant [R] and time 't' is shown below. Which of the given order of reaction is indicated by the graph?

The treatment of ethyl bromide with alcoholic silver nitrite gives :

Which of the following aqueous solutions will have the highest freezing point?

Match the type of cell given in Column I with their use given in Column II.

Assertion (A): The solubility of aldehydes and ketones in water decreases with increase in size of the alkyl group.

Reason (R): Aldehydes and ketones have dipole-dipole interaction.

Assertion (A): The boiling points of alkyl halides decrease in the order RI > RBr > RCl > RF.

Reason (R): The van der Waals forces of attraction decrease in the order RI > RBr > RCl > RF.

Assertion (A): For measuring resistance of an ionic solution an AC source is used.

Reason (R): Concentration of ionic solution will change if DC source is used.

Assertion (A): Henry's law constant ($K_H$) decreases with increase in temperature.

Reason (R): As the temperature increases, solubility of gases in liquids decreases.

Calculate the elevation of boiling point of a solution when 3 g of CaCl$_2$ (Molar mass = 111 g mol$^{-1}$) was dissolved in 260 g of water, assuming that CaCl$_2$ undergoes complete dissociation. ($K_b$ for water = 0.52 K kg mol$^{-1}$)

Liquids 'X' and 'Y' form an ideal solution. The vapour pressure of pure 'X' and pure 'Y' are 120 mm Hg and 160 mm Hg respectively. Calculate the vapour pressure of the solution containing equal moles of 'X' and 'Y'.

Based on the data given below, give plausible reason for the variation of conductivity and molar conductivity with concentration:

Give any two differences between order and molecularity of a reaction.

For a reaction X + Y → Z, in which both X and Y follow first order kinetics; if the concentration of X is increased 2 times and concentration of Y is increased 3 times, how does it affect the rate of reaction?

Write the mechanism of dehydration of ethyl alcohol with conc. H$_2$SO$_4$ at 443 K.

Carboxylic acid is more acidic than phenol. Give reason.

Give a chemical test to distinguish between benzaldehyde and acetophenone.

Shweta mixed two liquids A and B of 10 mL each. After mixing, the volume of the solution was found to be 20.2 mL.

(i) Why was there a volume change after mixing the liquids?

(ii) Will there be an increase or decrease of temperature after mixing?

(iii) Give one example for this type of solution.

(i) How does sprinkling of salt help in clearing the snow covered roads in hilly areas?

(ii) What happens when red blood cells are kept in 0.5% (mass/vol) NaCl solution? Justify your answer.

(iii) Write an application of reverse osmosis.

For the reaction A + B → Products, the following initial rates were obtained at various initial concentrations of reactants:

Determine the order of the reaction with respect to A and B and overall order of the reaction.

Write the name and structure of a hexadentate ligand.

Why is $[\text{Ni(CN)}_4]^{2-}$ square planar while $[\text{Ni(CO)}_4]$ is tetrahedral? [Atomic number : Ni = 28]

Haloarenes are less reactive towards nucleophilic substitution reactions. Account for this.

p-Dichlorobenzene has higher melting point than ortho and meta isomers. Account for this.

Tertiary alkyl halides are least reactive towards S$_N$2 reaction. Account for this.

Write the chemical equation for the following:

(i) Preparation of phenol from cumene

(ii) Nitration of anisole

Complete the following:

$(\text{CH}_3)_3\text{C}–\text{O}–\text{CH}_3 + \text{HI} \rightarrow$

Write the products formed in the following reactions:

(a) CH$_3$CHO + NH$_2$CONHNH$_2$ →

(b) CH$_3$CHO $\xrightarrow{\text{dil. NaOH}}$

(c) CH$_3$COOH $\xrightarrow{\text{Cl}_2/\text{red P, then H}_2\text{O}}$

Name the vitamin which is responsible for coagulation of blood.

What is meant by denaturation of protein? Give an example.

Read the passage and answer:

Carbohydrates are polyhydroxy aldehydes or ketones that represent enormous structural diversity in terms of the arrangement of atoms in space, resulting in hundreds of stereoisomers. Structural variants, which arise due to a different arrangement of atoms in three-dimensional space are known as stereoisomers. The number of stereoisomers can be theoretically estimated by using the formula 2$^n$, where 'n' is the number of stereocenters or asymmetric (chiral) carbon atoms in a molecule.

(a) Give chemical reactions to show the presence of an aldehydic group and straight chain in glucose.

What is the difference between a complex and a double salt?

(i) Arrange the following complexes in the increasing order of conductivity of their solution:

$[\text{Cr(NH}_3)_3\text{Cl}_3]$, $[\text{Cr(NH}_3)_6]\text{Cl}_3$, $[\text{Cr(NH}_3)_5\text{Cl}]\text{Cl}_2$

OR

(ii) Write two differences between primary and secondary valences in coordination compounds.

Give reasons for the following:

(I) Ce$^{4+}$ in aqueous solution is a good oxidising agent.

(II) The actinoid contraction is greater from element to element than lanthanoid contraction.

(III) $E°_{\text{Zn}^{2+}/\text{Zn}}$ value is more negative than expected, whereas $E°_{\text{Cu}^{2+}/\text{Cu}}$ is positive.

While studying the periodic properties, Arti came across an abnormal behaviour in the atomic size of Hf. She found that, even though Hf is placed below Zr in the same group, both have almost similar atomic sizes.

(I) Which phenomenon is responsible for the above behaviour? Define it.

(II) Mention any other consequence of the above phenomenon.

Give reasons for the following:

(I) Transition metals exhibit catalytic properties.

(II) Transition metals have high enthalpy of atomisation.

(III) Sc is a transition element, while Zn is not.

For a galvanic cell, the following half reactions are given. Decide, which will remain as reduction reaction and which will be reversed to become an oxidation reaction. Give reason for your answer.

(I) Cr$^{3+}$ + 3e$^-$ → Cr(s); E° = −0.74 V

(II) Fe$^{2+}$ + 2e$^-$ → Fe(s); E° = −0.44 V

Represent the cell in which the following reaction takes place:

$\text{Mg(s)} + 2\text{Ag}^+(0.001\,\text{M}) \rightarrow \text{Mg}^{2+}(0.100\,\text{M}) + 2\text{Ag(s)}$

Calculate $E_{cell}$ if $E°_{cell} = 3.17$ V. [log 10 = 1]

State Kohlrausch's law. Give any two applications of it.

$\Lambda^\circ_m$ NH$_4$Cl, $\Lambda^\circ_m$ NaOH and $\Lambda^\circ_m$ NaCl are 129.8, 217.4, and 108.9 S cm$^2$ mol$^{-1}$ respectively. Molar conductivity of $1 \times 10^{-2}$ M solution of NH$_4$OH is 9.33 S cm$^2$ mol$^{-1}$. Calculate the degree of dissociation ($\alpha$) of NH$_4$OH solution at this concentration.

In a chemistry practical class, the teacher gave his students an amine 'X' having molecular formula C$_2$H$_7$N, and asked the students to identify the type of amine. One of the students, Neeta, observed that it reacts with C$_6$H$_5$SO$_2$Cl, to give a compound which dissolves in NaOH solution. Can you help Neeta to identify the compound 'X'?

Arrange the following in the increasing order of their pK$_b$ value in aqueous phase:

C$_6$H$_5$NH$_2$, (CH$_3$)$_2$NH, NH$_3$, CH$_3$NH$_2$, (CH$_3$)$_3$N

Aniline on nitration gives considerable amount of meta product along with ortho and para products. Why?

Convert aniline to:

(I) p-bromoaniline

(II) phenol

Arun heated a mixture of ethylamine and CHCl$_3$ with ethanolic KOH, which forms a foul smelling gas. Write the chemical equation involved.

Identify A and B in the following reactions:

Convert aniline to:

(I) Benzene

(II) Sulphanilic acid

Werner's coordination theory in 1893 was the first attempt to explain the bonding in coordination complexes. Werner was able to explain that in complexes, the metal shows two different sorts of valency: primary and secondary. Primary valences are normally ionisable whereas secondary valences are non ionisable.

One mole of CrCl$_3 \cdot$ 4H$_2$O precipitates one mole of AgCl when treated with excess of AgNO$_3$ solution.

Write (i) the structural formula of the complex, and (ii) the secondary valency of Cr.

Which of the following molecules is chiral in nature?

Which of the following aldehydes will undergo Cannizzaro reaction?

In which of the following groups are both ions coloured in aqueous solution?

I. Cu$^+$ II. Ti$^{4+}$ III. Co$^{2+}$ IV. Fe$^{2+}$

[Atomic number : Cu = 29, Ti = 22, Co = 27, Fe = 26]

When pyrolusite ore is fused with KOH, in presence of air, a dark green coloured product 'A' is obtained which changes to purple coloured compound 'B' in acidic medium.

(I) Write the formulae of 'A' and 'B'.

(II) Write the ionic equation for the reaction when compound 'B' reacts with Fe$^{2+}$ in acidic medium.

Define anomers.

Draw the structure of $\beta$-D-Glucopyranose.

Sucrose is known as invert sugar. Explain.