Chemistry 11 past paper 2025

The third ionization potential value of an element is significantly high as compared to its 1st and 2nd ionization potentials. The element belongs to:

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Write down electronic configuration of: $_{29}Cu^{+2}$, $_{33}As$, $_{35}Br^{-1}$

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What is mass spectrometry? Explain the construction and working of a mass spectrometer. How can average atomic mass of an element be calculated from data obtained?

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Which pair of elements will most likely form an ionic bond?

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What is meant by **Catenation**? What is its importance in organic chemistry?

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Explain formation of covalent bonds in $O_2$ molecule on the basis of molecular orbital theory and valence bond theory. Justify that molecular orbital theory is superior to valence…

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Briefly explain the structure of $PCl_3$ and $NH_4^+$ ion on the basis of VSEPR theory.

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Describe by giving balanced chemical equations and necessary conditions that how a Carboxylic acid can be prepared from: a) $CH_3-CH_2-Cl$ b) $CH_3-CH_2-CH_2-OH$ c) $C_6H_5-CHO$

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The number of molecules present in $67.2\text{ dm}^3$ of $He$ gas at STP is:

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Write down the chemical tests with equations to identify chlorides, bromides and iodides present in aqueous solution.

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How can one identify the functional groups in the following compounds by chemical tests? Elaborate. a) $CH_3CHO$ b) $CH_3-CH_2-OH$ c) $CH_3-CH=CH_2$

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What will be the enthalpy of solution of $NaCl$ if $\Delta H$ (reverse lattice) is $+786\text{ kJ/mol}$ and $\Delta H$ (hyd) is $-783\text{ kJ/mol}$?

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Keeping in view the factors affecting bond energy, justify the order of bond energies in the following: a) Cl₂ > F₂ b) H₂ > HBr c) N₂ > O₂

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Why is Ethene more reactive than Ethane? Write down the reactions of Ethene with: a) $H_2SO_4 / H_2O$ b) $Cl_2 / H_2O$

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The following equilibrium will **NOT** be shifted in the forward direction by: ($N_2 + 3H_2 \rightleftharpoons 2NH_3 + \Delta$)

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Describe any three properties of water which are due to hydrogen bonding.

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What is solubility product? Derive an expression for the solubility product of $CaF_2$. How can the concept of solubility product be applied to predict the precipitation of $CaF_2$…

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Aqueous solution of which of the following salts will have pH less than 7?

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Write down three differences between limiting and non-limiting reactants.

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Explain the occurrence of a chemical reaction with reference to molecular collisions, activation energy, formation of activated complex and enthalpy changes in the reaction.

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Position of an element in periodic table with electronic configuration $1s^2, 2s^2p^6, 3s^2p^2$ is:

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Write down the reaction of Ethyl Bromide with $KOH_{(aq)}$, $NH_3$ and $AgNO_3$.

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Peroxyacetyl nitrate (PAN) is formed by the reaction of oxides of nitrogen with:

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State any three differences between crystalline and non-crystalline solids.

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Which of the following halides can reduce $H_2SO_4$ to $H_2S$?

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Briefly describe the terms 'shell', 'sub-shell' and 'orbital'.

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Identify the step in the mechanism of free radical chlorination of ethane: $CH_3-CH_3 + Cl^{\bullet} \longrightarrow CH_3-CH_2^{\bullet} + HCl$

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Why is the enthalpy of solution for $NH_4NO_3$ equal to $+25.7\text{ kJ/mol}$ (endothermic process) whereas that of $CaCl_2$ is $-83.0\text{ kJ/mol}$ (exothermic process)? Explain…

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Identify the product formed when Ethyl Bromide is warmed with $NaOH$ in ethanol:

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What is acid rain? Describe its formation with the help of chemical reactions involved.

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Which reagent is used for the reduction of Carboxylic acids to Alcohols?

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Write down any three measures that ensure the preservation of water resources.

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The compound which gives Silver mirror test as well as Iodoform test is:

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How can iodoform test be applied to the alcohols? Describe by giving chemical equations.

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Which pair of organic compounds can be distinguished by using 2,4-DNPH?

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Why aqueous solution of $Na_2CO_3$ is basic whereas that of $NH_4Cl$ is acidic? Justify by giving chemical equations.

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Identify correct relationship for determination of half-life of a first order reaction:

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How can ethylamine be prepared from: a) an alkyl halide b) a nitrite c) an amide

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Which of the following organic compound can be identified by Fehling solution test?

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Determine the principal energy level and number of valence electrons in the different sub-shells and orbitals of an element present in 3rd period and group-VIA of the periodic tabl…

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Write down the mechanism of base catalysed nucleophilic addition reaction of formaldehyde ($HCHO$) with $HCN$.

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Describe the use of compounds of sulphur in any three chemical industries.

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State Markovnikov's rule by giving an example and its mechanism.

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Calculate the volume occupied by $3.011 \times 10^{24}$ molecules of $NH_3$ gas enclosed in a container at STP.

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How is ethanol prepared from: a) Alkene b) Alkyl halide c) Carboxylic acid

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Briefly describe β-elimination reaction by giving a suitable example.

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Write down the reactions of 1-Propanol with: a) $SOCl_2$ b) $PCl_5$ c) Conc. $H_2SO_4$ / $180°C$

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Calculate $K_c$ for the following reaction at equilibrium at $100^{\circ}C$: $2SO_{2(g)} + O_{2(g)} \rightleftharpoons 2SO_{3(g)}$ $[SO_2] = 0.59\text{ M}, [O_2] = 0.05\text{ M}, […

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Calculate total entropy change when $NaCl$ dissolves in water under standard conditions: $NaCl_{(s)} \longrightarrow Na^+_{(aq)} + Cl^-_{(aq)}$ $S^{\circ}(NaCl) = 72.1\text{ J/mol/…

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Draw Born-Haber cycle for the formation of $KCl$. (Calculation is **NOT** required)

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For the reaction $N_2O_4 \longrightarrow 2NO_2$, the concentration of $N_2O_4$ is reduced from $0.1\text{ M}$ to $0.05\text{ M}$ in $60\text{ sec}$. If reaction is $1^{\text{st}}$…

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