CBSE 2025, Set 1 Solutions
CBSE Chemistry (2025)

In case of association, the abnormal molar mass of solute will

Standard electrode potential for $\text{Sn}^{4+}/\text{Sn}^{2+}$ couple is +0.15 V and that for the $\text{Cr}^{3+}/\text{Cr}$ couple is $-$0.74 V. The two couples in their standard states are connected to make a cell. The cell potential will be

The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin-only magnetic moment value of $\text{Cr}^{3+}$ ion (Atomic no. : Cr = 24) is ________.

Acidified KMnO$_4$ oxidises sulphite to

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

(i) $(\text{CH}_3)_2\text{CH–CH}_2\text{Br}$

(ii) $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br}$

(iii) $(\text{CH}_3)_3\text{C–Br}$

The correct order is

Alkyl halides undergoing nucleophilic bimolecular substitution reaction involve

Which is the correct order of acid strength from the following?

The acid formed when propyl magnesium bromide is treated with CO$_2$ followed by acid hydrolysis is

The best reagent for converting propanamide into propanamine is

An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because ________.

Assertion (A): $[\text{Cr(H}_2\text{O)}_6]\text{Cl}_2$ and $[\text{Fe(H}_2\text{O)}_6]\text{Cl}_2$ are examples of homoleptic complexes.

Reason (R): All the ligands attached to the metal are the same.

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

Reason (R): The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.

Assertion (A): The boiling point of ethanol is higher than that of methoxymethane.

Reason (R): There is intramolecular hydrogen bonding in ethanol.

Assertion (A): All naturally occurring $\alpha$-amino acids except glycine are optically active.

Reason (R): Most naturally occurring amino acids have L-configuration.

Give reason: Cooking is faster in a pressure cooker than in an open pan.

On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of deviation from Raoult's law is shown by the resulting solution? What change in temperature would you observe after mixing liquids X and Y?

Define Azeotrope. What type of Azeotrope is formed by negative deviation from Raoult's law? Give an example.

Would you expect benzaldehyde to be more reactive or less reactive in nucleophilic addition reactions than propanal? Justify your answer.

Identify A and B in the following reaction sequence:

$\text{CH}_3\text{CH}_2\text{Cl} \xrightarrow{\text{NaCN}} A \xrightarrow{\text{H}_2/\text{Ni}} B$

Identify A and B in the following reaction sequence:

$\text{C}_6\text{H}_5\text{NH}_2 \xrightarrow{\text{NaNO}_2/\text{HCl},\,0\text{–}5°\text{C}} A \xrightarrow{\text{C}_6\text{H}_5\text{NH}_2/\text{H}^+} B$

Write the reactions involved when D-glucose is treated with the following reagents:

(a) HCN

(b) Br$_2$ water

A solution of glucose (molar mass = 180 g mol$^{-1}$) in water has a boiling point of 100.20 °C. Calculate the freezing point of the same solution. Molal constants for water $K_f$ and $K_b$ are 1.86 K kg mol$^{-1}$ and 0.512 K kg mol$^{-1}$ respectively.

State the following:

(i) Kohlrausch law of independent migration of ions

(ii) Faraday's first law of electrolysis

Using $E°$ values of X and Y given below, predict which is better for coating the surface of iron to prevent corrosion and why?

Given: $E°_{X^{2+}/X} = -2.36$ V, $E°_{Y^{2+}/Y} = -0.14$ V, $E°_{Fe^{2+}/Fe} = -0.44$ V

A certain reaction is 50% complete in 20 minutes at 300 K and the same reaction is 50% complete in 5 minutes at 350 K. Calculate the activation energy if it is a first order reaction.

$[\text{R} = 8.314 \text{ J K}^{-1}\text{ mol}^{-1};\; \log 4 = 0.602]$

The elements of 3d transition series are: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.

Copper has exceptionally positive $E°_{M^{2+}/M}$ value. Why?

The elements of 3d transition series are: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.

Which element is a strong reducing agent in +2 oxidation state and why?

The elements of 3d transition series are: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.

Zn$^{2+}$ salts are colourless. Why?

Draw the structure of the major monohalo product for each of the following reactions:

(a) 4-chloro-1-ethylbenzene + Br$_2$, Heat $\rightarrow$ ?

(b) 1-methylcyclohexene + HBr $\rightarrow$ ?

(c) 4-(hydroxymethyl)phenol + HCl, Heat $\rightarrow$ ?

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

$(\text{CH}_3)_2\text{NH}$, $\text{CH}_3\text{CH}_2\text{NH}_2$, $\text{CH}_3\text{CH}_2\text{OH}$

Give plausible explanation for each of the following:

(i) Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.

(ii) Amides are less basic than amines.

What is the difference between native protein and denatured protein?

Which one of the following is a disaccharide?

Glucose, Lactose, Amylose, Fructose

Which vitamin is responsible for the coagulation of blood?

Read the passage and answer:

The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. The sum of powers of the concentration of reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously to bring about a chemical reaction is called molecularity of the reaction.

(a) (i) What is a rate determining step?

(a) (ii) Define complex reaction.

(b) What is the effect of temperature on the rate constant of a reaction?

Why is molecularity applicable only for elementary reactions whereas order is applicable for elementary as well as complex reactions?

The conversion of molecule X to Y follows second order kinetics. If concentration of X is increased 3 times, how will it affect the rate of formation of Y?

Read the passage and answer:

Phenols undergo electrophilic substitution reactions readily due to the strong activating effect of OH group attached to the benzene ring. Since the OH group increases electron density more at o– and p– positions, it is ortho, para-directing. The Reimer-Tiemann reaction introduces an aldehyde group on the aromatic ring of phenol, ortho to the hydroxyl group.

What happens when phenol reacts with:

(i) Br$_2$/CS$_2$

(ii) Conc. HNO$_3$

Why does phenol not undergo protonation readily?

Which is a stronger acid — phenol or cresol? Give reason.

OR

Write the IUPAC name of the product formed in the Reimer-Tiemann reaction.

Write the cell reaction and calculate the e.m.f. of the following cell at 298 K:

$\text{Sn(s)}\,|\,\text{Sn}^{2+}\,(0.004\,\text{M})\,||\,\text{H}^+\,(0.02\,\text{M})\,|\,\text{H}_2\text{(g)}\,(1\,\text{Bar})\,|\,\text{Pt(s)}$

(Given: $E°_{\text{Sn}^{2+}/\text{Sn}} = -0.14$ V, $E°_{\text{H}^+|\text{H}_2\text{(g)},\text{Pt}} = 0.00$ V)

Account for the following:

(i) On the basis of E° values, O$_2$ gas should be liberated at the anode but it is Cl$_2$ gas which is liberated in the electrolysis of aqueous NaCl.

(ii) Conductivity of CH$_3$COOH decreases on dilution.

Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.

Calculate the potential for the half-cell containing 0.01 M K$_2$Cr$_2$O$_7$(aq), 0.01 M Cr$^{3+}$(aq) and $1.0 \times 10^{-4}$ M H$^+$(aq).

The half cell reaction is: $\text{Cr}_2\text{O}_7^{2-}(aq) + 14\text{H}^+(aq) + 6e^- \rightarrow 2\text{Cr}^{3+}(aq) + 7\text{H}_2\text{O}(l)$

Standard electrode potential E° = 1.33 V. [Given: log 10 = 1]

Low spin tetrahedral complexes are not known. Account for this.

Co$^{2+}$ is easily oxidised to Co$^{3+}$ in the presence of a strong ligand. Explain. [At. No. of Co = 27]

What type of isomerism is shown by the complex $[\text{Co(NH}_3)_6][\text{Cr(CN)}_6]$?

Why is a solution of $[\text{Ni(H}_2\text{O)}_6]^{2+}$ green while a solution of $[\text{Ni(CN)}_4]^{2-}$ is colourless? (At. No. of Ni = 28)

Write the IUPAC name of the following complex: $[\text{Co(NH}_3)_5(\text{CO}_3)]\text{Cl}$

What is meant by "Chelate effect"? Give an example.

Write the hybridization and magnetic behaviour of $[\text{Fe(CN)}_6]^{4-}$. (Atomic number: Fe = 26)

If PtCl$_2 \cdot$ 2NH$_3$ does not react with AgNO$_3$, what will be its formula?

Carry out the following conversions:

(i) Ethanal to But-2-enal

(ii) Propanoic acid to ethane

The correct IUPAC name of $[\text{Pt(NH}_3)_2\text{Cl}_2]$ is

Which of the following statements is not true about glucose?

Complete and balance the following chemical equations:

(a) $2\text{MnO}_4^-(aq) + 10\text{I}^-(aq) + 16\text{H}^+(aq) \rightarrow$

(b) $\text{Cr}_2\text{O}_7^{2-}(aq) + 6\text{Fe}^{2+}(aq) + 14\text{H}^+(aq) \rightarrow$

How do you convert:

(a) Chlorobenzene to biphenyl

(b) Propene to 1-iodopropane

(c) 2-bromobutane to but-2-ene

An alkene A with molecular formula C$_5$H$_{10}$ on ozonolysis gives a mixture of two compounds B and C. Compound B gives positive Fehling test and also reacts with iodine and NaOH solution. Compound C does not give Fehling solution test but forms iodoform. Identify the compounds A, B and C.

An organic compound (A) (molecular formula C$_8$H$_{16}$O$_2$) was hydrolysed with dilute sulphuric acid to get a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives But-1-ene. Identify (A), (B) and (C) and write chemical equations for the reactions involved.