Please refer to Class 12 Chemistry Sample Paper Term 2 With Solutions Set A below. These Class 12 Chemistry Sample Papers will help you to get more understanding of the type of questions expected in the upcoming exams. All sample guess papers for Chemistry Class 12 have been designed as per the latest examination pattern issued by CBSE. Please practice all Term 2 CBSE Sample Papers for Chemistry in Standard 12.
Sample Paper Term 2 Class 12 Chemistry With Solutions Set A
1. (a) Why are carboxylic acids stronger than phenol? Justify.
(b) Write the structure of 2, 4 – DNP of benzaldehyde.
(c) Write reaction of cyclopropanone with hydroxyl amine
Answer. (a) It is because carboxylate ion is more stable than phenoxide ions due to dispersal of charge on two oxygen.
2. Give reasons. (2)
(a) It is not possible to determine Ʌm for weak electrolyte graphically.
(b) Ʌ° of HCl is greater than that of NaCl.
Answer. (a) It is because a curve cannot be extrapolated.
(b) Ʌ°HCl is more than Ʌ°NaCl because ionic mobility of H+ is more than that of Na+ since it is lighter than Na+.
3. How will you carry out following conversions.
(a) Acetaldehyde to lactic acid
(b) Acetone to propane
4. An organic compound ‘A’ with molecular formula C4H8O2 was hydrolysed with dil. H2SO4 to give a carboxylic acid ‘B’ and an alcohol ‘C’. ‘C’ on dehydration gives ethene and ‘C’ also on oxidation gives back ‘B’. Identify ‘A’, ‘B’ and ‘C’ and write the chemical equations for the reactions involved. (3)
Answer. ‘A’ is CH3COOCH2CH3 (Ethyl ethanoate), ‘B’ is ethanoic acid and ‘C’ is ethanol
5. The resistance of a conductivity cell filled with 0.1 mol L−1 KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 mol L−1 KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 mol L−1 KCl solution. The conductivity of 0.1 mol L−1 KCl solution is 1.29×10−2 S cm−1
6. Complete the following.
How will you convert.
(a) Aniline to Fluorobenzene
(b) Benzamide to Benzyl amine
(c) Ethanamine to N,N-Diethyl ethanamine
7. Answer the following questions.
(a) Which of the following is most effective electrolyte for coagulation of AgI/Ag+ sol?
MgCl2, K2SO4, K4[Fe(CN)6]
(b) What happens when a freshly precipitated Fe(OH)3 is shaken with small amount of FeCl3.
(c) Out of sulphur sol and proteins, which one forms macromolecular colloid?
Answer. (a) K4[Fe(CN)6] is most effective because [Fe(CN)6]4– has highest charge.
(b) Fe(OH)3 precipitate is converted into colloidal state by preferential adsorption of Fe3+ ions.
(c) Proteins will form macromolecular colloid.
8. An organic compound ‘A’ with molecular formula C7H7NO reacts with Br2/aqKOH to give a compound ‘B’, which upon reaction with NaNO2 and HCl at 0°C gives ‘C’. Compound ‘B’ on further reaction with Br2 water gives white precipitate of ‘D’. Identify ‘A’, ‘B’, ‘C’ and ‘D’, and write the reactions involved.
Complete the following:
Answer. A is C6H5–CONH2, benzamide, ‘B’ is aniline, ‘C’ is benzene diazonium chloride, ‘D’ is 2,4,6 – tribromoaniline.
9. (a) Write the formula of the coordination compound Tetraamine aqua chlorido cobalt (III) chloride.
(b) Give two examples of ambidentate ligands.
(c) Predict the geometry of [Ni(CN)4]2–
Answer. (a) [Co(NH3)4(H2O)Cl]Cl2
(b) CN− , NO−2 SCN− , are examples of ambidentate ligands. (Any two)
(c) It has dsp2 hybridisation and square planar geometry.
(a) Write IUPAC name of (i) [Co(NH3)6]3+ (ii) [NiCl4]2–
(b) What is hybridisation and shape of [Ni(CO)4]. [Atomic number of Ni = 28]. Is it diamagnetic or paramagnetic.
Answer. (a) (i) Hexaammine cobalt (III) (ii) Tetrachloridonickelate (II)
(b) Ni(28) [Ar] 4s2 3d8
Ni(0) [Ar] 4s0 3d10
10. Following ions are given.
Cr2+, Cu2+, Cu+, Fe2+, Fe3+, Mn3+ Identify the ion which is
(a) strong reducing agent (b) unstable in aqueous solution.
(c) a strong oxidising agent.
Answer. (a) Cr2+ is strong reducing agent because it can lose one electron to form Cr3+ (t2g
3) which is half filled and more stable.
(b) Cu+ is unstable in aqueous solution and disproportionate to Cu2+ and Cu because hydration enthalpy of Cu2+ ions overcome second ionisation enthalpy.
(c) Mn3+ can gain electron to form Mn2+ (3d5) which is more stable, that is why Mn3+ is strong oxidising agent.
11. Give suitable reason in each.
(a) Why are Zn, Cd, Hg non-transition elements?
(b) Which transition metal of 3d series does not show variable oxidation state?
(c) Why are melting points of transition metals high?
Answer. (a) It is because neither they nor their ions have incompletely filled d-orbitals.
(b) Sc and Zn
(c) It is due to strong metallic bonds as they have unpaired electrons, therefore strong interatomic attraction.
(a) Why is Cu2+ ion blue coloured while Zn2+ ion colourless in aqueous solution?
(b) Why is separation of mixture of lanthanoid elements difficult?
(c) Why are Zn, Cd, Hg soft metals and have low melting points?
Answer. (a) Cu2+ has one unpaired electrons, undergoes d-d-transition by absorbing light from visible region and radiates blue colour where as Zn2+ does not have unpaired electron.
(b) It is due to similar ionic size due to lanthanide contraction. Their resemble in properties making separation difficult.
(c) It is due to weak metallic bonds due to large size and absence of unpaired electrons
12. Read the passage given below and answer the questions that follow.
The rate of reaction which may also be called the velocity or speed can be defined with the relation to the concentration of any of the reacting substances or to that of any product of reaction. If the species chosen is a reactant which has a concentration ‘c’ at time ‘t’, the rate will be – (dc/dt) while the rate with reference to the product having a concentration ‘x’ at time ‘t’ is dc/dt Any concentration units may be used for expressing the rate, thus if mol L–1 is used for concentration and seconds for the time, the units for rate are mol L–1 s–1. For reactions, pressure units are sometimes used in place of concentration, so that legitimate units for rate would be (mmHg) s–1 and atm s–1.
The order of a reaction concerns the dependence of the rate upon the concentrations of reacting substances; thus, if the rate is found experimentally to be proportional to the αth power of the concentration of one of the reactant ‘A’, to the βth power of the concentration of a second reactant ‘B’, so rate = k [A]α [B]β, the order of reaction is ‘α’ w.r.t. ‘A’ and ‘β’ w.r.t ‘B’ and overall order is α + B.
(Source: Laidler KJ & Glasstone S (1948), Rate, order and molecularity in chemical kinetics, Journal of chemical education, 25(7). 383)
(a) Give an example of reaction with fractional order.
(b) What is half life of zero order reaction?
(c) What is unit of ‘k’ for first order reaction if time is measured in seconds?
(d) The decomposition of NH3 on platinum surface is zero order reaction. What are rates of production of N2 and H2 if k = 2.5 × 10–4 mol L–1 s–1? (2)
For the reaction 2A + B → A2B, the rate = k [A] [B]2 with k = 2.0 × 10–6 mol–2 L2 s–1. Calculate the rate of reaction when [A] = 0.1M and [B] = 0.2 mol L–1.
Answer. (a) H2 + Br2 → 2HBr, rate = k [H2]1 [Br2]1/2