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# Board Paper of Class 12-Science 2015 Chemistry All India(SET 2) - Solutions

General Instructions :
(i) All questions are compulsory.
(ii) Q. no. 1 to 5 are very short answer questions and carry 1 mark each.
(iii) Q. no. 6 to 10 are short answer questions and carry 2 marks each.
(iv) Q. no. 11 to 22 are also short answer questions and carry 3 marks each.
(v) Q. no. 23 is a value based question and carry 4 marks.
(vi) Q. no. 24 to 26 are long answer questions and carry 5 marks each.
(vii) Use log tables if necessary, use of calculators is not allowed.
• Question 1
Zn2+ salts are white while Cu2+ salts are coloured. Why ? VIEW SOLUTION
• Question 2
Which would undergo SN1 reaction faster in the following pair:
VIEW SOLUTION
• Question 3
How much charge is required for the reduction of 1 mol of Zn2+ to Zn? VIEW SOLUTION
• Question 4
Write the dispersed phase and dispersion medium of butter. VIEW SOLUTION
• Question 5
Write the IUPAC name of the given compound:
VIEW SOLUTION
• Question 6
Write the structures of the following molecules:

(i) H2SO3
(ii) XeOF4 VIEW SOLUTION
• Question 7
Write down the IUPAC name of the complex [Pt(en)2Cl2]2+. What type of isomerism is shown by this complex?

OR

Using IUPAC norms write the formulate for the following coordination compounds :

(i) Hexaamminecobalt (III) chloride
(ii) Potassium tetrachloridonickelate (II) VIEW SOLUTION
• Question 8
Define rate of reaction? Write two factors that affect the rate of reaction. VIEW SOLUTION
• Question 9

Arrange the following in increasing order of their basic strength :

(i) C6H5 – NH2, C6H5 – CH2 – NH2, C6H5 – NH – CH3

VIEW SOLUTION
• Question 10
Why does a solution containing non-volatile solute have higher boiling point than the pure solvent ? Why is elevation of boiling point a colligative property ? VIEW SOLUTION
• Question 11
(i) What is the principle behind the zone refining of metals?
(ii) What is the role of silica in the extraction of copper?
(iii) How is 'cast iron' different from 'pig iron'? VIEW SOLUTION
• Question 12
Give reasons for the following :
(i) N2 is less reactive at room temperature.
(ii) H2Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.
(iii) Helium is used in diving apparatus as a diluent for oxygen. VIEW SOLUTION
• Question 13

(a) Write the hybridization and shape of the following complexes :

(i) [CoF6]3–

(ii) [Ni(CN)4]2–

(Atomic number : Co = 27, Ni = 28)

(b) Out of NH3 and CO, which ligand forms a more stable complex with a transition metal and why?

VIEW SOLUTION
• Question 14
How do you convert the following:
(i) C6H5CONH2 to C6H5NH2
(ii) Aniline to phenol
(iii) Ethanenitrile to ethanamine

OR

Write the chemical equations involved when aniline is treated with the following reagents:
(i) Br2 water
(ii) CHCI3 + KOH
(iii) HCI VIEW SOLUTION
• Question 15
Write the names and structures of the monomers of the following polymers:
(i) Buna-S
(ii) Glyptal
(iii) Polyvinyl chloride VIEW SOLUTION
• Question 16
(i) Write the product obtained when D-glucose reacts with H2N − OH.
(ii) Amino acids show amphoteric behaviour. Why?
(iii) Why cannot vitamin C be stored in our body? VIEW SOLUTION
• Question 17
Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2) is dissolved in 500 g of water. (Kf for water = 1.86 K kg mol–1) VIEW SOLUTION
• Question 18

Define the following terms :

(i) Primitive unit cells

(ii) Schottky defect

(iii) Ferromagnetism VIEW SOLUTION
• Question 19
Write the structure of the major product in each of the following reactions :
VIEW SOLUTION
• Question 20
Give reasons for the following :
(i) Phenol is more acidic than ethanol.
(ii) Boiling point of ethanol is higher in comparison to methoxymethane.
(iii) (CH3)3C − O − CH3 on reaction with HI gives CH3OH and (CH3)3C − I as the main products and not (CH3)3C − OH and CH3I. VIEW SOLUTION
• Question 21
The rate constant of a first order reaction increases from 2 × 10−2 to 4 × 10−2 when the temperature changes from 300 K to 310 K. Calculate the energy of activation (Ea).
(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)
VIEW SOLUTION
• Question 22
Define the following terms :
(i) Brownian movement
(ii) Peptization
(iii) Multimolecular colloids VIEW SOLUTION
• Question 23
Seeing the growing cases of diabetes and depression among young children, Mr. Lugani, the principal of on reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning junk food in schools and introducing healthy snacks and drinks like soup, lassi, milk, etc. in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the morning assembly. After six months, Mr. Lugani conducted the health survey is most of the schools and discovered a tremendous improvement in the health of the students.

(i) What are the values (at least two) displayed by Mr. Lugani?
(iii) What are antidepressant drugs? Give an example.
(iv) Name the sweetening agent used in the preparation of sweets for a diabetic patient. VIEW SOLUTION
• Question 24
Calculate e.m.f. and ∆G for the following cell:

Given :

OR

(a) The conductivity of 0.20 mol L−1 solution of KCl is 2.48 × 10−2 S cm−1. Calculate its molar conductivity and degree of dissociation (α). Given λ0 (K+) = 73.5 S cm2 mol−1 and λ0 (C1) = 76.5 S cm2 mol−1.

(b) What type of battery is mercury cell? Why is it more advantageous than dry cell? VIEW SOLUTION
• Question 25

(a) Account for the following :

(i) Zr and Hf have almost similar atomic radii.

(ii) Transition metals show variable oxidation states.

(iii) Cu+ ion is unstable in aqueous solution.

(b) Complete the following equations :

(i) 2 MnO2 + 4 KOH + O2 →

(ii) 2 Na2CrO4 + 2 H + →​

OR

​(a)

 ${\mathrm{E}}_{\left({\mathrm{M}}^{2}+/\mathrm{M}\right)}^{0}$ Cr Mn Fe Co Ni Cu –0.91 –1.18 –0.44 –0.28 –0.25 –0.34

From the given data of E0 values, answer the following questions :

(i) Why is ${\mathrm{E}}_{\left({{\mathrm{Cu}}^{2}}^{+}/\mathrm{Cu}\right)}^{0}$ value exceptionally positive?

(ii) Why is ${\mathrm{E}}_{\left({{\mathrm{Mn}}^{2}}^{+}/\mathrm{Mn}\right)}^{0}$ value highly negative as compared to other elements?

(iii) Which is a stronger reducing agent Cr2+ or Fe2+? Give reason.

(b) Why do actinoids show a wide range of oxidation states? Write on similarity between the chemistry of lanthanoids and actinoids.

VIEW SOLUTION
• Question 26

(a) A compound 'A' of molecular formula C2H3OCl undergoes a series of reactions as shown below. Write the structures of A, B, C and D in the following reactions :

(b) Distinguish between the following :

(i) C6H5 − COCH3 and C6H5 − CHO

(ii) Benzoic acid and methyl benzoate

(c) Write the structure of 2-methylbutanal.

OR

(a) Write the structures of the main products when acetone (CH3 − CO − CH3) reacts with the following reagents :

(i) Zn − Hg/conc. HCl

(ii) H2N − NHCONH2/H+

(iii) CH3MgBr and then H3O+

(b) Arrange the following in the increasing order of their boiling points :

C2H5OH, CH3 − CHO, CH3 − COOH

(c) Give a simple chemical test to distinguish between the following pair of compounds :

CH3CH2CHO and CH3CH2COCH3

VIEW SOLUTION
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