Chemistry

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If the rate constant of a reaction is 0.03 s^-1, how much time does it take for 7.2 mol L^-1 concentration of the reactant to get reduced to 0.9 mol L^-1?(Given: log 2 = 0.301) Answer: 1. 69.3 s Key idea: the unit mathrms⁻¹ means first order: t=2.303/klog[A]₀/[A] . 7.2/0.9=8 , log8=3×0.301=0.903 . t=2.303×0.903/0.03... Integrated rate equations and half-life (zero and first order) 1 answer
Higher yield of NO in N_2(g) + O_2(g) ⇌ 2NO(g) can be obtained at[Δ H of the reaction = + 180.7 kJ mol^-1]A. higher temperatureB. lower temperatureC. higher concentration of N_2D. higher concentration of O_2Choose the correct answer from the options… Answer: 4. A, C, D only Key idea: Le Chatelier's principle. Δ H>0 (endothermic): higher temperature favours NO, so A is right and B is wrong... Delta G and equilibrium, factors affecting equilibrium, Le Chatelier's principle 1 answer
Which one of the following reactions does NOT belong to "Lassaigne's test"? Answer: 4. mathrm2CuO + C xrightarrowΔ 2Cu + CO₂ Key idea: Lassaigne's test fuses the organic compound with sodium to convert N, S and halog... Qualitative analysis: detection of N, S, P, halogens 1 answer
Sugar 'X'A. is found in honey.B. is a keto sugar.C. exists in α and β - anomeric forms.D. is laevorotatory.'X' is : Answer: 2. D-Fructose Key idea: match each property. D-Fructose is present in honey, is a keto sugar (ketohexose), exists as α and β anomers... Carbohydrates: classification, glucose, fructose 1 answer
Match List I with List II.List I (Name of Vitamin): A. Vitamin B_12 B. Vitamin D C. Vitamin B_2 D. Vitamin B_6List II (Deficiency disease): I. Cheilosis II. Convulsions III. Rickets IV. Pernicious anaemiaChoose the correct answer from the options giv… Answer: 2. A-IV, B-III, C-I, D-II Vitamin mathrmB₁₂ : pernicious anaemia (IV). Vitamin D: rickets (III). Vitamin B₂ (riboflavin): cheilosis... Vitamins 1 answer
Identify the correct orders against the property mentioned :A. H_2O > NH_3 > CHCl_3 - dipole momentB. XeF_4 > XeO_3 > XeF_2 - number of lone pairs on central atomC. O-H > C-H > N-O - bond lengthD. N_2 > O_2 > H_2 - bond enthalpyChoose the correct ans… Answer: 1. A, D only A true: H₂O (1.85 D) > NH₃ (1.47 D) > CHCl₃ (1.04 D). B false: lone pairs on Xe are XeF₄ = 2, XeO₃ = 1, XeF₂ = 3, so th... Electronegativity, Fajan's rule, dipole moment 1 answer
Match List - I with List - IIList-I: A. XeO_3 B. XeF_2 C. XeOF_4 D. XeF_6List-II: I. sp^3d; linear II. sp^3; pyramidal III. sp^3d^3; distorted octahedral IV. sp^3d^2; square pyramidalChoose the correct answer from the options given below : Answer: 1. A-II, B-I, C-IV, D-III Key idea: count bond pairs and lone pairs on Xe. XeO₃ : 3 bonds + 1 lone pair, sp³ , pyramidal (II). XeF₂... VSEPR theory and shapes of molecules 1 answer
C(s) + 2H_2(g) → CH_4(g); Δ H = -74.8 kJ mol^-1Which of the following diagrams gives an accurate representation of the above reaction? [R → reactants; P → products] Answer: 1. Energy diagram (1) Key idea: Δ H=-74.8 kJ/mol means an exothermic reaction: products lie 74.8 kJ below the reactants. Diagram (1)... Hess's law and enthalpies of reactions (bond dissociation, combustion, formation etc.) 1 answer
The standard heat of formation, in kcal/mol of Ba^2+ is :[Given : standard heat of formation of SO_4^2- ion (aq) = -216 kcal/mol, standard heat of crystallisation of BaSO_4(s) = -4.5 kcal/mol, standard heat of formation of BaSO_4(s) = -349 kcal/mol] Answer: 1. -128.5 Key idea: mathrmBa²⁺(aq)+SO₄²⁻(aq)→ BaSO₄(s) has Δ H=-4.5 kcal (crystallisation). Δ H_f(BaSO₄)=Δ H_f(mathrmBa²⁺)+Δ H_f(mat... Hess's law and enthalpies of reactions (bond dissociation, combustion, formation etc.) 1 answer
Given below are two statements :Statement I : Ferromagnetism is considered as an extreme form of paramagnetism.Statement II : The number of unpaired electrons in a Cr^2+ ion (Z = 24) is the same as that of a Nd^3+ ion (Z = 60).In the light of the abo… Answer: 3. Statement I is true but Statement II is false Statement I is true: ferromagnetism is the extreme form of paramagnetism (domains a... Colour, catalytic and magnetic properties, complexes, interstitial compounds, alloys 1 answer
Match List - I with List - IIList-I: A. Haber process B. Wacker oxidation C. Wilkinson catalyst D. Ziegler catalystList-II: I. Fe catalyst II. PdCl_2 III. [(PPh_3)_3RhCl] IV. TiCl_4 with Al(CH_3)_3Choose the correct answer from the options given belo… Answer: 3. A-I, B-II, C-III, D-IV Haber process: Fe catalyst (I). Wacker oxidation (ethene to ethanal): PdCl₂ (II). Wilkinson catalyst: [(PP... Colour, catalytic and magnetic properties, complexes, interstitial compounds, alloys 1 answer
For the reaction A(g) ⇌ 2B(g), the backward reaction rate constant is higher than the forward reaction rate constant by a factor of 2500, at 1000 K.[Given : R = 0.0831 L atm mol^-1 K^-1]K_p for the reaction at 1000 K is Answer: 3. 0.033 Key idea: K_c=k_f/k_b and K_p=K_c(RT)^(Δ n) . k_b=2500 k_f , so K_c=1/2500=4×10⁻⁴ . Δ n=2-1=1 ; RT=0.0831×1000=83.1 . K_p=4... Law of chemical equilibrium, Kp and Kc 1 answer
How many products (including stereoisomers) are expected from monochlorination of the following compound?(CH_3)_2CH-CH_2-CH_3 Answer: 4. 6 Key idea: count the distinct kinds of hydrogen in 2-methylbutane, then count stereoisomers. Two equivalent CH₃ on C-2: 1-chloro... Alkanes: conformations, halogenation mechanism 1 answer
Which one of the following compounds does not decolourize bromine water? Answer: 1. cyclohexane Key idea: bromine water is decolourised by alkenes (addition) and by activated aromatics (substitution). Styrene: C=C... Alkenes: geometrical isomerism, electrophilic addition, Markovnikov and peroxide effect 1 answer
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).Assertion (A) : (primary alkyl iodide drawn as zig-zag chain ending in I) undergoes S_N2 reaction faster than (the corresponding alkyl chloride,… Answer: 1. Both A and R are true and R is the correct explanation of A Key idea: in S_N2 the rate depends on how easily the leaving group de... Mechanisms of substitution reactions (SN1/SN2) 1 answer
The correct order of decreasing basic strength of the given amines is : Answer: 3. N-ethylethanamine > ethanamine > N-methylaniline > benzenamine Key idea: aliphatic amines are stronger bases than aromatic ones,... Basic character of amines 1 answer
Given below are two statements :Statement I : Benzenediazonium salt is prepared by the reaction of aniline with nitrous acid at 273 - 278 K. It decomposes easily in the dry state.Statement II : Insertion of iodine into the benzene ring is difficult a… Answer: 1. Both Statement I and Statement II are correct Statement I is correct: diazotisation of aniline with NaNO₂/HCl is done at 273-278... Diazonium salts in synthesis 1 answer
The major product of the following reaction is :Reactant: Ph-CO-CH2CH2-CN; (i) CH_3MgBr (excess); (ii) H_3O^+ Answer: 2. structure (2) Key idea: Grignard reagent adds to both the ketone and the nitrile, but the nitrile adduct is hydrolysed to a keton... Aldehydes and ketones: HCN, NH3 derivatives, Grignard, oxidation, reduction (Wolff-Kishner, Clemmensen) 1 answer
Identify the suitable reagent for the following conversion.Methyl benzoate (Ph-COOCH3) → benzaldehyde (Ph-CHO) Answer: 2. (i) AlH(iBu)₂ (ii) H₂O Key idea: partial reduction of an ester to an aldehyde needs DIBAL-H at low temperature. AlH(i-Bu)₂ follow... Aldehydes and ketones: HCN, NH3 derivatives, Grignard, oxidation, reduction (Wolff-Kishner, Clemmensen) 1 answer
The correct order of decreasing acidity of the following aliphatic acids is : Answer: 3. HCOOH > CH₃COOH > (CH₃)₂CHCOOH > (CH₃)₃CCOOH Key idea: alkyl groups are electron-donating (+I) and destabilise the carboxylate io... Carboxylic acids: acidic strength 1 answer
Match List I with List IIList I (Mixture): A. CHCl_3 + C_6H_5NH_2 B. Crude oil in petroleum industry C. Glycerol from spent-lye D. Aniline - waterList II (Method of Separation): I. Distillation under reduced pressure II. Steam distillation III. Fract… Answer: 1. A-IV, B-III, C-I, D-II CHCl₃ + aniline: boiling points well apart (334 K vs 457 K), simple distillation (IV). Crude oil: fraction... Purification: crystallization, sublimation, distillation, differential extraction 1 answer
Which of the following aqueous solution will exhibit highest boiling point? Answer: 3. 0.01M Na₂SO₄ Key idea: elevation of boiling point depends on i× c . Urea: 1×0.01=0.01 . KNO₃ : 2×0.01=0.02 . Na₂SO₄ : 3×0.01=0.03... Colligative properties 1 answer
Match List - I with List - IIList-I (Example): A. Humidity B. Alloys C. Amalgams D. SmokeList-II (Type of Solution): I. Solid in solid II. Liquid in gas III. Solid in gas IV. Liquid in solidChoose the correct answer from the options given below : Answer: 2. A-II, B-I, C-IV, D-III Key idea: name the dispersed substance and the medium for each example. Humidity: water droplets/vapour in... Concentration terms: molality, molarity, mole fraction, percentage 1 answer
5 moles of liquid X and 10 moles of liquid Y make a solution having a vapour pressure of 70 torr. The vapour pressures of pure X and Y are 63 torr and 78 torr respectively. Which of the following is true regarding the described solution? Answer: 2. The solution shows negative deviation. Key idea: compare the observed vapour pressure with the Raoult's law value. x_X=5/15=1/3 ,... Vapour pressure and Raoult's law 1 answer

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