Chemistry 12 past paper 2025

Which of the following nuclei will be magnetically active in NMR spectroscopy?

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Justify the given statements: a. Al is considered as the best conductor in 3rd period elements. b. Size of Na⁺ is smaller than Na.

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What is Grignard's reagent? Outline the step by step synthesis of Propanoic Acid, 2-Propanol and Ethane using suitable Grignard reagent.

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The presence of specific functional groups in a molecule is commonly identified by:

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How does $Fe^{+2}$ act as a catalyst in the given reaction? Write its two-step mechanism: $S_2O_8^{2-} + 2I^- \xrightarrow{Fe^{+2}} 2SO_4^{2-} + I_2$

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What is mass spectrometry? Explain its working and its applications in determining the relative atomic mass.

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Which of the 3rd period elements has the highest melting point?

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Write two chemical reactions to show the acidic nature of $SO_3$.

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Provide the chemical reactions for the hydrolysis of Group-IV tetrahalides. Explain why carbon tetrahalides are not hydrolysed and describe the trend in ease of hydrolysis of tetra…

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Which of the following statement is correct regarding the density of Group-I elements?

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Why are group IIB and IIIB elements considered as non-typical transition elements?

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Explain the mechanism of nitration and Friedel-Crafts acylation of benzene, highlighting key steps and intermediates.

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Which sulphate of Group-II elements has the highest solubility in water?

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Complete and balance the given chemical equations.

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Write chemical equations to illustrate the basic nature of Group-I normal oxides, per-oxides and super oxides using $Na_2O$, $Na_2O_2$ and $NaO_2$ as examples.

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Coordination number in $[Cu(NH_2-NH_2)_2]SO_4$ is:

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Identify the type of synthesis (Partial or total) for each of the following: a. Conversion of Ethanol into Ethanal. b. Synthesis of vegetable Ghee from oil.

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Provide the chemical equations for the Nucleophilic addition reactions between: a. Acetone and Phenyl Hydrazine b. Acetaldehyde and 2,4-Dinitrophenyl Hydrazine c. Formaldehyde and…

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Identify the organic compound:

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Beryllium ($Be$) differs from other alkaline earth metals in terms of its reactions with hydrogen and alkalis. Describe these differences and provide the relevant chemical equation…

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By providing resonance structures of their conjugate bases, explain why the order of acidic strength is: $RCOOH > Phenol > Alcohol$

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Homolytic cleavage of covalent bond converts the bonded atoms into:

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Write chemical reactions of $KMnO_4$ in acidic medium with: a. $FeSO_4$ b. Mohr's Salt (Balancing is not necessary)

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Describe the effects of pH, Temperature and Substrate Concentration on enzyme activity. (Include a general graphical representation illustrating the optimum conditions for enzyme a…

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Which alcohol will yield alkenes more easily among the given options?

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Sodium and Magnesium belong to the same period but why is Sodium Carbonate more stable than Magnesium Carbonate?

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Which of the following alkyl halides is most likely to undergo an $SN_2$ reaction?

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Identify the type of isomerism in given pairs: a. 1-Chloro propane and 2-Chloro propane b. Butanone and Butanal c. Diethyl Ether and Methyl Propyl Ether

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Which alcohol is **NOT** the direct product of reaction when Grignard reagent reacts with aldehydes or ketones?

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Briefly explain the 'Coal' and 'Petroleum' as the source of organic compounds.

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Which alcohol will yield an immediately oily layer according to Lucas test?

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Briefly explain simple, conjugated and derived proteins with one example in each case.

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Which of the following will be more reactive towards nucleophilic addition reactions?

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Briefly describe any three types of adhesives.

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Carboxylic acids are reduced to which product on reaction with $LiAlH_4$?

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Describe two sources of oxides of Nitrogen and Sulphur with one environmental impact associated with each of these pollutants.

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Differentiate between qualitative and quantitative analysis with suitable example in each.

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Differentiate between addition and condensation polymers with suitable example in each.

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Ozone is being mainly destroyed by:

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How can ethanol and acetone be differentiated using I.R spectroscopy specifically through characteristic signals?

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Provide the chemical equation to illustrate how ozonolysis of an alkyne can be used to prepare two molecules of acetic acid.

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Explain why the basic strength of amines follows the order: Secondary amine > Primary amine > Tertiary amine

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Arrange the following alcohols in order of increasing reactivity towards the cleavage of O-H bond: Ethanol, 2-Methyl-2-Propanol and 2-Propanol.

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Which is the stronger acid between difluoroethanoic acid or trifluoroethanoic acid? Give reason.

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Write any three differences between $E_2$ and $E_1$ reactions of alkyl halides.

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What are the alternatives to ChloroFluoro carbons (CFCs)? How do they compare in terms of environmental impact and effectiveness?

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Write the mechanism of the given reaction: $2CH_3OH \xrightarrow[140^{\circ}C]{\text{Conc. } H_2SO_4} CH_3OCH_3 + H_2O$

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Briefly describe why ethanol exhibits three signals in its NMR spectrum, whereas acetone shows only one signal.

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Complete the given chemical equations: a. $CH_3COCl + CH_3COOH \rightarrow$ b. $CH_3COOC_2H_5 + LiAlH_4 \rightarrow$ c. $CH_3MgBr + CH_3CN \rightarrow$

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Write two chemical equations to show the amphoteric nature of $BeO$.

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