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CBSE
#1 Class Class 12 Chemistry Electrochemistry 2026 Short 5M
For the reaction :
$$2AgCl(s) + H_2(g)\ (0.4\ atm) \longrightarrow 2Ag(s) + 2H^+(0.1\ M) + 2Cl^-(0.2\ M)$$
Calculate emf of the cell at $25\ ^\circ C$.
Given : $\Delta G^\circ = -43500$ J $mol^{-1}$
$[\log 10 = 1,\ 1\ F = 96500\ C\ mol^{-1}]$

[This is the internal-choice (OR) alternative of Question 33.]
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CBSE
#2 Class Class 12 Chemistry Electrochemistry 2026 Short 5M
Calculate emf and $\Delta G$ for the following cell at 298 K :
$$Mg(s)\,|\,Mg^{2+}(0.01\ M)\,||\,Ag^+(0.001\ M)\,|\,Ag(s)$$
Given : $E^\circ_{Mg^{2+}/Mg} = -2.37$ V, $E^\circ_{Ag^+/Ag} = +0.80$ V
$[1\ F = 96500\ C\ mol^{-1},\ \log 10 = 1]$
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CBSE
#3 Class Class 12 Chemistry The d- and f-Block Elements 2026 Long 5M
Answer the following questions :
(i) Name a member of the lanthanoid series (I) which exhibits $+4$ oxidation state (II) which exhibits $+2$ oxidation state.
(ii) Why transition metals act as good catalyst ?
(iii) Why Cr has higher melting point than Mn ?
(iv) What happens when acidic solution of potassium permanganate is allowed to stand for sometime ? Give the equation involved. What is this type of reaction called ?

[This is the internal-choice (OR) alternative of Question 32.]
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CBSE
#4 Class Class 12 Chemistry The d- and f-Block Elements 2026 Long 5M
(i) From the given data of $E^\circ$ values, answer the following questions :
| $E^\circ_{M^{2+}/M}$ | V | Cr | Mn | Fe | Co | Ni | Cu |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Value (V) | $-1.18$ | $-0.91$ | $-1.18$ | $-0.44$ | $-0.28$ | $-0.25$ | $+0.34$ |
(I) Why $E^\circ_{M^{2+}/M}$ show irregular trend in the above values ?
(II) Why is $E^\circ_{Cu^{2+}/Cu}$ value exceptionally positive ?
(III) Why $E^\circ_{Mn^{2+}/Mn}$ value is highly negative ?
(ii) Write the ionic equations for the oxidising action of potassium permanganate for its reaction with $I^-$ in both acidic and alkaline solutions.
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CBSE
#5 Class Class 12 Chemistry Aldehydes, Ketones and Carboxylic Acids 2026 Long 5M
Answer the following questions :
(i) Draw structure of the 2, 4-dinitrophenyl hydrazone derivative of benzaldehyde.
(ii) Arrange the following in increasing order of their reactivity towards HCN :
Di-tert. butyl ketone, Acetaldehyde, Acetone
(iii) Give a simple chemical test to distinguish between benzoic acid and ethyl benzoate.
(iv) Write the name of the reagent to convert Ethanenitrile to Ethanal.(v) Draw the structure of 'X' in the following reaction : Cyclohexanol $\xrightarrow{CrO_3}$ 'X'

[This is the internal-choice (OR) alternative of Question 31.]
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CBSE
#6 Class Class 12 Chemistry Aldehydes, Ketones and Carboxylic Acids 2026 Long 5M
(i) An organic compound (X) has the molecular formula $C_5H_{10}O$. Draw structures for (X) if it :
(I) does not give Tollen's test but gives a positive iodoform test.
(II) does not give Tollen's test and iodoform test but undergoes Aldol condensation.
(III) undergoes Cannizzaro's reaction.
(ii) Show how each of the following compounds can be converted to benzoic acid :
(I) Acetophenone (II) Ethyl benzene
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CBSE
#7 Class Class 12 Chemistry Coordination Compounds 2026 Long 4M
The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometry of coordination compounds. The Crystal Field Theory (CFT) of coordination compounds is based on the effect of different crystal fields (provided by the ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields.

Answer the following questions :
(a) In octahedral crystal field, energies of which d-orbitals will be raised when ligands approach the central metal atom/ion ? Give reason in support of your answer.
(b) Using crystal field theory, write the electronic configuration of central metal atom/ion of the following :
(i) $[CoF_6]^{3-}$
(ii) $[Co(NH_3)_6]^{3+}$ [At. No. : Co = 27]
(c) Write hybridization and magnetic behaviour of the complex $[Fe(CN)_6]^{3-}$. [Atomic No. : Fe = 26]

[This row uses the internal-choice (OR) part (c) of Question 30.]
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CBSE
#8 Class Class 12 Chemistry Coordination Compounds 2026 Long 4M
The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometry of coordination compounds. The Crystal Field Theory (CFT) of coordination compounds is based on the effect of different crystal fields (provided by the ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields.

Answer the following questions :
(a) In octahedral crystal field, energies of which d-orbitals will be raised when ligands approach the central metal atom/ion ? Give reason in support of your answer.
(b) Using crystal field theory, write the electronic configuration of central metal atom/ion of the following :
(i) $[CoF_6]^{3-}$
(ii) $[Co(NH_3)_6]^{3+}$ [At. No. : Co = 27]
(c) $[NiCl_4]^{2-}$ is paramagnetic while $[Ni(CO)_4]$ is diamagnetic though both are tetrahedral. Why ? [Atomic No. : Ni = 28]
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CBSE
#9 Class Class 12 Chemistry Amines 2026 Long 4M
The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Aliphatic amines are stronger bases than ammonia whereas aromatic amines are weaker bases than ammonia. Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their high reactivity. Substitution tends to occur at ortho- and para-positions. Hinsberg reagent is used for the identification and distinction between primary, secondary and tertiary amines. Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes.

Answer the following questions :
(a) (i) Why $CH_3 - NH_2$ is a stronger base than $(CH_3)_3N$ in aqueous solution ?
(a) (ii) Write structural formulae of the compound A and B :
$$CH_3CONH_2 \xrightarrow{NaOBr} A \xrightarrow[\text{Base}]{C_6H_5COCl} B$$
(b) How can you convert aniline to benzonitrile ?
(c) Why is $-NH_2$ group of aniline acetylated before carrying out nitration ?

[This row uses the internal-choice (OR) part (b) of Question 29.]
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CBSE
#10 Class Class 12 Chemistry Amines 2026 Long 4M
The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Aliphatic amines are stronger bases than ammonia whereas aromatic amines are weaker bases than ammonia. Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their high reactivity. Substitution tends to occur at ortho- and para-positions. Hinsberg reagent is used for the identification and distinction between primary, secondary and tertiary amines. Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes.

Answer the following questions :
(a) (i) Why $CH_3 - NH_2$ is a stronger base than $(CH_3)_3N$ in aqueous solution ?
(a) (ii) Write structural formulae of the compound A and B :
$$CH_3CONH_2 \xrightarrow{NaOBr} A \xrightarrow[\text{Base}]{C_6H_5COCl} B$$
(b) A compound 'X' with molecular formula $C_3H_9N$ reacts with Hinsberg reagent to give a product insoluble in alkali. Identify 'X'.
(c) Why is $-NH_2$ group of aniline acetylated before carrying out nitration ?
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CBSE
#11 Class Class 12 Chemistry Haloalkanes and Haloarenes 2026 Short 3M
Compound 'X' with molecular formula $C_4H_9Br$ reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the concentration of the compound 'X'. When an optically active isomer 'Y' of the compound 'X' was treated with aqueous KOH solution, the rate of reaction was found to be dependent on concentration of compound 'Y' and aqueous KOH both.
(a) Write down the structural formula of both 'X' and 'Y'.
(b) Out of 'X' and 'Y', which one will undergo racemisation and why ?
(c) Out of 'X' and 'Y', which one will form product with inversion of configuration and why ?
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CBSE
#12 Class Class 12 Chemistry Alcohols, Phenols and Ethers 2026 Short 3M
Write the reaction involved in the following :
(a) Reimer-Tiemann reaction
(b) Kolbe's reaction
(c) Friedel-Crafts acylation of anisole
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#13 Class Class 12 Chemistry Aldehydes, Ketones and Carboxylic Acids 2026 Short 3M
Give reasons for the following :
(a) Carboxylic acids have higher boiling point than alcohols of comparable molecular masses.
(b) Alpha $(\alpha)$ hydrogens of aldehydes and ketones are acidic in nature.
(c) Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.
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CBSE
#14 Class Class 12 Chemistry Biomolecules 2026 Short 3M
Write the reactions of D-Glucose with the following :
(a) HI
(b) $Br_2$ water
(c) Conc. $HNO_3$
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CBSE
#15 Class Class 12 Chemistry Solutions 2026 Short 3M
Calculate the boiling point of a solution containing 0.61 g of benzoic acid (Molar mass $= 122$ g $mol^{-1}$) in 5 g of $CS_2$ in which it dimerises to the extent of 88%. The boiling point and $K_b$ of $CS_2$ are $46.2\ ^\circ C$ and $2.3$ K kg $mol^{-1}$ respectively.
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CBSE
#16 Class Class 12 Chemistry Electrochemistry 2026 Short 3M
What type of battery is Mercury cell ? Why it is more advantageous than dry cell ? Write overall reaction taking place in Mercury cell.

[This is the internal-choice (OR) alternative of Question 23.]
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CBSE
#17 Class Class 12 Chemistry Electrochemistry 2026 Short 3M
Answer the following :
(i) Why is the Equilibrium Constant $(K_c)$ related to $E^\circ_{cell}$ and not to $E_{cell}$ ?
(ii) Two metals 'A' and 'B' have standard electrode potential values of $-0.24$ V and $+0.80$ V respectively. Which of these will liberate hydrogen gas from dil. $H_2SO_4$ ?
(iii) Write the cell reaction which occurs in lead storage battery when it is in charging.
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CBSE
#18 Class Class 12 Chemistry Chemical Kinetics 2026 Short 3M
For the first order thermal decomposition reaction, following data was obtained :
$$C_2H_5Cl(g) \longrightarrow C_2H_4(g) + HCl(g)$$
| S. No. | Time (s) | Total Pressure (atm) |
| --- | --- | --- |
| 1 | 0 | 0.30 |
| 2 | 30 | 0.50 |

Calculate rate constant. [Given : $\log 3 = 0.48$]
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CBSE
#19 Class Class 12 Chemistry Chemical Kinetics 2026 Short 2M
Following reaction takes place in one step :
$$2A + B \longrightarrow 2C$$
How will the rate of above reaction change if the volume of the reaction vessel is decreased to one third of its original volume ? Will there be any change in the order of reaction with the reduced volume ?
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CBSE
#20 Class Class 12 Chemistry Biomolecules 2026 Short 2M
Differentiate between the following :
(i) Peptide linkage and Glycosidic linkage
(ii) Essential amino acids and Non-essential amino acids
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