Haryana Bseh Class 12 Chemistry — Real Previous-Year Papers

The molarity of a solution obtained by mixing 750 ml of 0.5 M HCl with 250 ml of 2 M HCl will be? (a) 1.00 M (b) 0.875 M (c) 1.25 M (d) 2.5 M

When vapour's of a compound X are passed over heated copper, the major product obtained is the acetone. The compound X is: (a) n-Propyl alcohol (b) Iso-propyl alcohol (c) Acetaldehyde (d) Propane

Fill in the blank: Due to ............... Zirconium (Zr) and Hafnium (Hf) have identical radii.

Fill in the blank: For a chemical reaction ............... can never be a fraction.

Fill in the blank: The element ............... has highest melting point among d-block elements.

Name the reaction: C6H5-COCl (benzoyl chloride) is converted to C6H5-CHO (benzaldehyde) using H2 / Pd-BaSO4.

How many structural isomers of C5H11Br are possible?

Among aldehydes or ketones which gives positive Tollen's Test?

Assertion [A]: Nitric acid and water form maximum boiling Azeotrope. Reason [R]: Azeotropes are binary mixture showing the same composition in liquid and vapour phase. (a) Both [A] and [R] are true and [R] is the correct explanation of [A]. (b) Both [A] and [R] are true, but [R] is not the correct explanation of [A]. (c) [A] is true, but [R] is false. (d) [A] is false, but [R] is true.

Assertion [A]: [Ni(CN)4]2- is a square-planar and diamagnetic. Reason [R]: It has no unpaired electrons due to presence of strong field. (a) Both [A] and [R] are true and [R] is the correct explanation of [A]. (b) Both [A] and [R] are true, but [R] is not the correct explanation of [A]. (c) [A] is true, but [R] is false. (d) [A] is false, but [R] is true.

Assertion [A]: 1-chlorobutane on heating with alc. KOH gives mainly Bute-1-ene. Reason [R]: Bute-1-ene is more stable than Bute-2-ene. (a) Both [A] and [R] are true and [R] is the correct explanation of [A]. (b) Both [A] and [R] are true, but [R] is not the correct explanation of [A]. (c) [A] is true, but [R] is false. (d) [A] is false, but [R] is true.

What is basic structural difference between starch and cellulose?

Match the following: Column-I: (i) Half life of first order reaction (ii) K[A]^(1/2)[B]^(1/2) (iii) Zero Order Reaction (iv) NH4NO2 -> N2 + 2H2O ; Column-II: (a) Order = 1 (b) Molecularity = 1 (c) t(1/2) = 0.693/K (d) K = (1/t)[R]0 - [R] **OR** The rate constant of a first order reaction is 60 sec^-1. How much time will it take to reduce the initial conc. of the reaction to its 1/16th value?

(a) Predict the number of unpaired electron in square-planar [Pt(CN)4]2- ion. [1 mark] (b) Write IUPAC name of K3[Fe(C2O4)3] compound. [1 mark]

(a) What happens when Ethyl amine is treated with chloroform in the presence of alc. KOH? [1 mark] (b) Why is it necessary to avoid traces of moisture during the use of Grignard reagent? [1 mark]

How are the following conversions carried out? [1 + 1 = 2] (a) Propene -> Propane-2-ol (b) Benzyl chloride -> Benzyl alcohol **OR** Give simple chemical test to distinguish between following pairs of compound: [1 + 1 = 2] (i) Ethanal and Propanone (ii) Propanal and Benzaldehyde

Complete the given sequence of reactions and identify the products from A to D: Benzene --(Conc. HNO3 / Conc. H2SO4)--> [A] --(H2/Ni)--> [B] --(HNO2/HCl, 0 deg to 5 deg C)--> [C] --(H2O/HCl)--> [D] **OR** Complete the given sequence of reactions and identify the products from A to D: CH3-CH2-CH2-OH --(KMnO4)--> [A] --(+NH3)--> [B] --(-H2O)--> [C] --(NaOH, Br2)--> [D]

(a) What gives the reaction of toluene with chlorine in presence of FeCl3 predominantly? [1 mark] (b) Out of Ethyl bromide and Ethyl Iodide, which one undergoes SN2 reaction faster? [1 mark]

The half life for radioactive decay of 14C is 5730 years. An archaeological artifact containing wood had only 80% of the 14C found in living tree. Estimate the age of the sample.

(a) Arrange these metals in their increasing order of the reducing power given the standard electrode potentials: K+/K = -2.93 V, Ag+/Ag = 0.80 V, Hg2+/Hg = 0.79 V, Mg2+/Mg = -2.37 V [2 marks] (b) Arrange the following metals in the order in which they displace each other from the aqueous solution of their salt: Al, Cu, Fe, Mg, Zn [1 mark]

Give equation of the following reactions: [1 x 3 = 3] (i) Oxidation of propane-1-ol with alkaline KMnO4 (ii) Bromine in CS2 with phenol (iii) Dilute HNO3 with phenol

(a) Write all the geometrical isomer's of [Pt(NH3)(Br)(Cl)(Py)] and how many of these will exhibit optical isomer's? [2 marks] (b) What is the oxidation number of Cobalt in K[Co(CO)4]? [1 mark] **OR** Explain the following: [1 x 3 = 3] (i) Ambident ligand (ii) Co-ordination sphere (iii) Co-ordination number

(a) Why are aliphatic amines stronger base than the aromatic amines, explain? [1.5 marks] (b) Write short note on 'Diazotisation'. [1.5 marks] **OR** Complete the following: [1 x 3 = 3] (i) C6H5N2Cl --[(i) HBF4, (ii) NaNO2/Cu, heat]--> ............. (ii) C6H5NH2 + Conc. H2SO4 -> ............. (iii) C6H5N2Cl + H3PO2 + H2O -> .............

Answer the following questions: (i) How does the solubility of gases in liquid depend on Temp? [1] (ii) Which condition is applied to increase the solubility of CO2 in soft drink? [1] (iii) Does the value of kH depend upon temp or not? Explain. [1] (iv) What condition of 'bends' is felt by scuba divers? [1] **OR** Case passage (Raoult's Law / Ideal solutions): The solutions which obey Raoult's law over the entire range of concentration are known as ideal solutions. Ideal solutions have two other important properties: the enthalpy of mixing of the pure components forming the solution is zero, and the volume of mixing is also zero. When a solution does not obey Raoult's law over the entire range of concentration, it is called a non-ideal solution. The vapour pressure of such a solution is either higher or lower than that predicted by Raoult's law. If it is higher, the solution exhibits positive deviation; if it is lower, it exhibits negative deviation from Raoult's law. Some liquids on mixing form azeotropes, which are binary mixtures having the same composition in the liquid and vapour phase, and boil at a constant temperature; in such cases it is not possible to separate the components by fractional distillation. There are two types of azeotropes, called minimum boiling azeotropes and maximum boiling azeotropes. Solutions that show a large positive deviation from Raoult's law form minimum boiling azeotropes at a specific composition. Answer the following questions: (i) Solutions which distil without any change in composition are called? [1] (ii) What type of azeotrope will be formed if 100 ml of liquid A is mixed with 50 ml of liquid B to form a 140 ml solution? [1] (iii) Give any two examples of maximum boiling azeotropes. [1] (iv) Which type of deviation will the mixture of HCl and water show? [1]

Questions: (i) Explain essentially the difference between the alpha-form of glucose and the beta-form of glucose. [2] (ii) Name the two monosaccharides obtained on hydrolysis of lactose sugar. [1] (iii) Write one difference between peptide linkage and glycosidic linkage. [1]

(i) Why does the conductivity of a solution decrease with dilution? [1] (ii) Write the reaction involved in the working of the H2-O2 fuel cell. [2] (iii) What is the potential of a hydrogen electrode which is in contact with a solution whose pH is 10? [2] **OR** (i) What is an electrochemical cell? Describe the working of the Zn-Cu cell. [2] (ii) What is a salt bridge? What is its function? [2] (iii) The conductivity of a 0.20 M solution of KCl at 298 K is 0.0248 S cm^-1. Calculate its molar conductivity. [1]

(i) Most of the transition metal ions exhibit characteristic colour in aqueous solution. [1] (ii) Many of the transition elements are known to form interstitial compounds, explain. [1] (iii) Transition metals and their compounds generally exhibit paramagnetic behaviour, why? [1] (iv) Cr2+ is a strong reducing agent, while Mn3+ with the same configuration is an oxidising agent, why? [1] (v) Zn, Cd and Hg are not typical transition elements, why? [1] **OR** Complete and balance the following chemical equations: [1 x 5 = 5] (i) Cr2O7²-(aq) + H2S(g) + H+(aq) -> ......... (ii) Cu2+(aq) + I-(aq) -> ......... (iii) Fe2+ + MnO4- + H+ -> ......... (iv) MnO4- + H2O + I- -> ......... (v) Na2Cr2O7 + KCl -> .........

An organic compound 'A' with molecular formula C6H7N is treated with NaNO2 and dil. HCl, and compound 'B' is formed. Compound 'B' further reacts with H3PO2 and water to form an aromatic compound 'C'. On Friedel-Crafts alkylation, compound 'C' gets converted into compound 'D' having molecular formula C7H8. In the presence of light, this compound gets converted into compound 'E' on reaction with chlorine. Write the structures of compounds A to E, and write the chemical equations also. **OR** Explain the following: [1 x 5 = 5] (i) Acetylation (ii) Decarboxylation (iii) Aldol condensation (iv) Clemmensen reduction (v) Wolff Kishner reduction