Mock Board-1

(2018 -19)
Date : ___________
Class
Duration : 3 Hours Chemistry XII
Max. Marks : 70

Instructions:
1. The question paper has 27 questions in all and all questions are compulsory.
2. Questions from serial no. 1 to 5 carries 1 mark each.
3. Questions from serial no. 6 to 12 carry 2 marks each
4. Questions from serial no. 13 to 24 carry 3 marks each
5. Questions 25 to 27 carry 5 marks each.

1. In case of chemisorptions, why adsorption first increases and then decreases? [1]
2. Arrange the following in increasing order of boiling point: [1]
n - Pentylchloride, iso - Pentylchloride, neo - Pentylchloride
3. Name the type of crystal defect which is produced when NaCl crystal is doped with MgCl2? [1]
4. What is the role of crtyolite in metallurgy of Aluminium? [1]
5. Name one reagent used for separation of primary, secondary and tertiary amines. [1]
6. Give a chemical reaction to represent each: [2]
(a) Sandmeyer’s reaction (b) Kolbe’s reaction
7. (a) What is the role of depressant in froth floatation method? [2]
(b) Out of C and CO which is better reducing agent for FeO.
(i) In the lower part of blast furnance (higher temperature)
(ii) In the upper part of blast furnance (lower temperature)
OR
(a) What is the thermodynamic criteria for the feasibility of the reaction?
(b) Which method of purification is represented by the following reaction
523 K 1700 K
Ti(s ) + 2l2 (g )  
→ Ti l4 (g )  → Ti(s ) + 2I2 (g )
8. 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? [2]
9. (a) Give the structure of H3PO2. [2]
(b) Why is H3PO3 diprotic?
10. (a) State kohlrausch law. [2]
(b) Calculate l m for acetic acid, if l (H ) = 349.65 S cm mol and l (CH3COO ) = 54.65 S cm2
0 0 + 2 –1 0 –

mol–1.
11. Write reactions to confirm the following in glucose. [2]
(a) presence of an aldehyde group
(b) one primary alcoholic group

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 Half Yearly Examination (2018-19)
12. Give one structural and one functional difference between DNA and RNA. [2]
13. (a) Give the mechanism of the following reaction: [3]
Conc. H2SO4, 413K
2 CH3CH2OH CH3CH2OCH2CH3
Does the reaction follow S N
1
or S
N
2
pathway?
14. Complete the following reaction equations: [3]
(a) XeF4 + H2O → (b) H3PO3  ∆
→ (c) XeF6 + H2O →

15. (a) How many faraday of charge is required to convert 1 mole of MnO4– to Mn2+ ion? [3]
(b) Calculate the emf and ΔG of the cell reaction
Zn(s)| Zn2+ (0.0004 M) || Cd2+ (0.2M) |Cd (s)
E0Zn2+/Zn = -0.769 V; E0Cd2+/Cd = –0.403 V, [log 2 = 0.3010]
16. (a) What are biodegradable polymers? Give an example. [3]
(b) Give the structures of monomers of:
(i) Nylon – 6 (ii) Teflon
17. Write the chemical equations involved when aniline is treated with the following reagents:
(i) Br2 water (ii) CHCl3+ KOH (iii) HCI. [3]
18. Niobium crystallizes in a body centered cubic structure. If density is 8.55 g cm–3, calculate
atomic radius of niobium, given that its atomic mass is 93u. [3]
19. (a) How does catalyst work? [3]
(b) Give the expression of freundlich adsorption isotherm.
(c) What is meant by peptization.
20. Give reasons: [3]
(a) Interhalogen compounds are more reactive than halogens.
(b) PCl5 is known but NCl5 is not known.
(c) Amongst all noble gases only xenon is known to form compounds with oxygen and fluorine.
21. Using IUPAC, write the name of [Ni(NH3)6]2+. Explain [Ni(NH3)6]2+ is an outer orbital complex.
Predict its hybridization. [3]
OR
Give the formula of the coordination entity in which Co3+ ion is bound to one Cl– , one NH3 molecule
and two bidentate ethylenediamine (en) molecules. Write the name of given coordination entity.
22. (a) Out of 0.1 mol solution of glucose and NaCl respectively, which one will have higher
boiling point? [3]
(b) A solution is prepared by dissolving 8.95 mg of a gene fragment in 35.0 ml of water has an
osmotic pressure 46.9 atm. Assuming the gene fragment is a non- electrolyte determine
its molar mass.
23. Writhe the equations involved when: [3]
(a) Salicylic acid is treated with acetyl chloride in presence of base.
(b) 2,4,6-trinitrochlorobenzene is subject to hydrolysis.
(c) Methyl chloride is treated with AgCN.
24. (a) What are tranquilizers? [3]
(b) Why is the use of aspartame is limited to cold food and drinks?
(c) Name a compound which act as both antiseptic and disinfectant.
25. Explain the following: [5]
(a) Actinoids show large number of oxidation state.
(b) The transition metals form a large number of complex compounds
(c) Chromium is a typically hard metal while Hg is liquid.

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Half Yearly Examination (2018-19)

(d) MnO is basic while Mn2O7 is acidic in nature.

(e) Silver is a transition metal but Zn is not.
OR
(a) Give the consequences of lanthanoid contraction.
(b) Complete the following reactions.
(i) MnO4– + S2O32– + H2O → (ii) Cr2O72– + Sn2+ + H+ →
(c) Which of the following has maximum number of unpaired electrons?
Ti3+, V3+ , Fe2+ , Mg2+
(d) Based on data arrange Fe2+, Mn2+ and Cr2+ in increasing order of stability of +2 oxidation
state.
E0Cr3+/2+ = -0.4 V ; E0Mn3+/2+ = 1.5V ; E0Fe3+/2+ = 0.80 V
26. (a) A compound ‘A’ with molecular formula C5H10O gave a positive 2,4-DNP test but a negative
Tollen’s test. It was oxidized to carboxylic acid ‘B’ with molecular formula C3H6O2 when
treated with salt of ‘B’ gave a hydrocarbon ‘C’ on klolbe’s electrolytic reduction. Identify A,
B and C. [5]
(b) Account for the following:
(i) Acetaldehyde give aldol whereas formaldehyde not.
(ii) Carboxylic acids do not give reaction of carbonyl group.
OR
(a) Complete the following equations:

(i)

(ii)

(b) State the sequence of steps to obtain:

(i) Acetophenone from benzene

(ii) Acetone from acetylchloride

27. (a) For a first order reaction ,show that time required for 99% completion of a first order
reaction is twice the time required for the completion of 90%. [5]
(b) The decomposition of phosphine, PH3, proceeds according to following equation:
4PH3(g) → P4 (g)+ 6 H2 (g)
It is found that the reaction follows following rate equation:
Rate=K [PH3]
The half life of PH3 is 35.9 min. at 120°C.
(i) How much time is required for the 3/4th of PH3 to decompose. [log 4 = 0.6020]
(ii) What fraction of original sample of PH3 remains behind after 2 minute?
[antilog(0.01670) = 0.0453]
OR
Consider the reaction
2A + B → C+D

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 Half Yearly Examination (2018-19)

Following results were obtained in experiments designed to study the rate of reaction.
Exp. No. Initial concentration (mol L’1) Initial rate of formation
[A] [BI [D] (M/min)
1 0.10 0.10 1.5 × 10–3
2 0.20 0.20 3.0 × 10–3
3 0.20 0.40 6.0 × 10
(а) Write the rate law for the reaction.
(b) Calculate the value of rate constant for the reaction.
(c) Which of the following possible reaction mechanisms is constant with the rate law found
in (a)?
I. A + B → C + E (slow) A + E → D (fast)
II. B→ C + E (slow) A + E → F (fast)
A + F → D (fast)

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 Hints/Solutions to Mock Board-1
(2018 -19)
Date : ___________
Class
Duration : 3 hours Chemistry XII
Max. Marks : 70
8. When we add a non-volatile solute to a pure solvent the vapour pressure of solution decreases, therefore, it is to be
heated to higher temperature so that its vapour pressure becomes equal to the atmospheric pressure, i.e. its boiling
point will be higher.
Elevation of boiling point is a colligative property because it depends upon the number of particles of solute and not on
nature of solute.
17.

dx
27. = k [ A ]x [B ]y
dt
1.5 × 10–3 = k(0.1)x (0.1)y ,..(i)
3.0 × 10–3 = k(0.20)x (0.20)y ,..(ii)
6.0 × 10 = k(0.20) (0.40)
–3 x y
,..(iii)
Dividing (ii) by (iii), we get
1 1
= y ⇒ 2y = 21 ⇒ y = 1
2 2

Dividing (i) by (ii), we get

1
1 1 1 1
= ×   ⇒ x = 1 ⇒ 2x = 1 ⇒ 2x = 20 ⇒ x = 0
2 2x  2  (2)

dx
= k [ A ]0 [B ]1
(a) dt

1.5 × 10−3 −2 −1
(b) 1.5 × 10–3 = k(0.1)1 ⇒ k = 0.1 = 1.5 × 10 min
(c) (II) B → C + E (slow) is the possible reaction mechanism which is in agreement with the
rate law, = k[B].

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