Chemistry 12 past paper 2024

Reducing smog contains high concentration of:

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Write chemical equations to show what happens when the following compounds are heated: a. $LiNO_3$ b. $NaNO_3$ c. $Mg(NO_3)_2$

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Justify that $CO_2$ is an acidic oxide. How do the dioxides of $Ge$, $Sn$, and $Pb$ differ in nature from $CO_2$? Explain by giving two chemical reactions for each in support of yo…

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Which one is NMR inactive nucleus?

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What is the difference between the functional groups present in the following pairs of compounds? a. Acid halides and Acid amides b. Ethers and Esters c. Aldehydes and Ketones

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How is the refining of Crude oil carried out? State the basic principle involved and explain the steps in industrial process. (Do not describe the fractions)

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In which of the following pairs both elements have no tendency to form dichlorides?

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Write down the electronic configuration of Copper and Chromium. Why do these electronic configurations violate the Aufbau principle?

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Why Carbon and Silicon show +4 oxidation states whereas Ge, Sn and Pb show +4 as well as +2 oxidation states in their compounds? Explain. Also compare the relative stability of +4…

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Describe the geometries of complex ions with coordination number 4 and 6.

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Explain the structure of Benzene on the basis of molecular orbital concept. How does this concept justify the stability of benzene? Why does benzene preferably give electrophilic s…

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Which of the following elements will react with $O_2$ to form an **amphoteric oxide**?

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State Fajan's rule and justify it by giving two examples.

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How can Acetyl Chloride be prepared from carboxylic acid? Write down the reactions of $CH_3-C(=O)-Cl$ with: a. Acetic acid b. Ethanol c. $NH_3$

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Identify the colourless complex ion:

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Write down the reactions of Acetic anhydride with: a. $H_2O$ b. $NH_3$ c. $C_2H_5OH$

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Describe lipids. How can essential and non-essential lipids be differentiated? Write down the following reactions of a general triglyceride: a. Hydrolysis b. Saponification

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Identify the functional group in the compound formed by the reaction of an alcohol with a carboxylic acid:

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Justify that the restricted rotation about C-C bond in 1,2-dimethyl cyclopropane is responsible for geometrical isomerism.

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What is mass spectrometry? Write down its basic principle. Explain the construction and working of a mass spectrometer.

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How can aldehydes and ketones be differentiated by giving two chemical tests?

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What is the order of acidic strength of phenol, alcohol and carboxylic acid? Justify your answer by giving $pK_a$ values, and stability of their conjugate bases.

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Which of the following alkenes on ozonolysis produces formaldehyde only?

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Write down the mechanism of $S_N1$ reactions.

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Predict which of the following compound is more basic:

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Write down three differences between addition and condensation polymerization.

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In Kolbe-Schmitt reaction, phenol is reacted with:

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How do $Cr_2O_7^{2-}$ and $CrO_4^{2-}$ ions exist in equilibrium with one another? How can they be interconverted due to this equilibrium?

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An alcohol reacts with $PBr_3$ as $3R-OH + PBr_3 \rightarrow 3R-Br + H_3PO_3$. The reactivity of alcohol will be greater if it is:

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Briefly describe enzyme inhibition. What are its types?

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Which of the following will undergo aldol condensation reaction with a mild base?

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How can 1-Butyne be prepared using a suitable vicinal dihalide and a geminal dihalide? Give chemical reactions with conditions.

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All the acid derivatives can be converted back into corresponding carboxylic acid by their reaction with:

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What is the greenhouse effect? Give its brief description.

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Which of the following nitrogenous bases is **NOT** present in DNA?

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Write down the reactions of Phenol with conc. $HNO_3$, aq. $Br_2$ and conc. $H_2SO_4$.

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Nylon-6,6 is the polymer of:

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Describe the type of electronic transition that occurs when UV-Vis radiations of 200-800 nm wavelength are passed through $CH_2=CH-CH_2-OH$.

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Write down three differences between E1 and E2 reactions.

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Describe the significance of Functional group region and Finger print regions in the IR spectrum.

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Justify that $Al(OH)_3$ is amphoteric but $Mg(OH)_2$ is basic.

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Write down the reactions of $CH_3-CH_2-Mg-Br$ with: a. Acetone b. $CO_2$.

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Describe anomalous trends in the ionization energies of elements of 3rd period in the periodic table.

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Why is Acetaldehyde more reactive than Acetone in nucleophilic addition reactions?

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Write down two reactions in which O-H bond of alcohol is broken. What is reactivity order of different alcohols in these reactions?

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What is the role of chloro-fluoro carbons (CFCs) in destroying the ozone layer in the stratosphere?

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Write down the chemical reactions for the following observations: a. Calcium when heated in air (containing O₂ and N₂) results in the formation of two compounds. b. One of the abov…

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Naturally occurring magnesium has three isotopes: $Mg-24$ (mass=24 amu, 78.70%), $Mg-25$ (mass=25 amu, 10.13%), $Mg-26$ (mass=26 amu, 11.17%). Calculate relative atomic mass of $Mg…

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How can ethene be converted into: a. Ethanol b. Ethylene chlorohydrin

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Acetone undergoes aldol condensation reaction with a mild base. Write down the mechanism of this reaction of acetone.

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