K V MANKAPUR
Ist Pre Board
Sub-Chemistry
Class-XII
Time : 3 hrs.
M.M.70
Instructions:1. All Questions’ are compulsory.
2. Internal Choice has been given in 2,3,5 marks Questions.
3. Question No 1 to 5 are very short answer questions carrying 1 mark each.
4. Question No 6 to 10 are Short answer question’s carrying 2 marks each.
5. Question No 11 to 22 are Short answer question’s carrying 3 marks each.
6. Question No 23 (VBQ) is of 4 marks.
7. Question No 24 to 26 are Long answer question’s carrying 5 marks each.
8. Use Log table if necessary.
1. Name a compound which shows both Frenkel and Schottky defect.
2.What happens when CH2=CH-C≡CH reacts with one mole of HCl? Write chemical equation.
3. Draw the structure of 2-Hydroxy benzaldehyde.
4. Arrange the following alcohols in increasing order of acidic character:
CH3CH2OH, CH3OH, CH3CH2CH2OH, CH3CH2CH2CH2OH
5.What is meant by sorption?
6. How does molar conductivity of strong electrolyte and weak electrolyte vary with concentration? Explain.
Or
Kc for a given cell reaction is 10. Calculate E0cell.
A(s) + B+(aq)= A+(aq) +B(s)
7. Write two differences between order and molecularity of a reaction.
8. (i)Give one example each of reducing and non-reducing sugar.
(ii) Differentiate between DNA and RNA,
9. What are biocatalysts? Give an example.
10. (a) What happens when glucose reacts with bromine water? Write chemical reaction involved.
(b) Give one difference between globular and fibrous protiens.
11. Convert:
(i) Phenol to salicyclic acid.
(ii) Ethanol to ethanoic acid
(iii) Anisole to 4- methyl anisole
12 (i) Why is Cu2+paramagnetic whereas Cu+ diamagnetic?
(ii) Why is Fe2+ smaller than Mn2+?
(iii) Draw the structure of Permanganate ion.
13. NaCl has fcc structure. Calculate its density if edge length is 562 pm and molar mass is 58.5 g mol -1.
Or
(i) What are ferromagnetic substances? Give an example.
(ii) In which type of defect , density decreases?
(iii) What are 13-15 compounds?
14(a) Describe the following giving the chemical equation:
(i) Hoffmann’s Bromamide Reaction
(ii) Gabriel Phthalimide synthesis
(b) Explain why aniline is weaker base than cyclohexylamine?
15. The following data were obtained during the first order thermal dcomposition of SO 2Cl2 at a constant volume.
SO2Cl2 (g) → SO2 (g) +Cl2 (g)
Experiment
Time in Second
Total pressure in atm.
1
0
0.4
2
100
0.7
Calculate the rate constant.
16. (I) Write the expression for the Freundlich adsorption isotherm for the adsorption of gases on solids in the form
of equation.
(ii)Draw a graph showing Freundlich adsorption isotherm.
(iii)What is the value of slope and intercept?
17.(a) Mn2+ compounds are more stable than Fe2+ towards oxidation to +3 state. Why?
(b) In 3d-transition series, which element is not regarded as transition metal and why?
© Which bivalent cation in 3d-transition series is the most paramagnetic and why?
18. (a) Write IUPAC name of [ Co(H20)4 (NH3)2]Cl3
(b) Discuss the shape and magnetic moment of [ Ni(CN)4]2- and [ NiCl4]219 (a) write the mechanism of the following reaction :
CH3CH2OH + HCl→ CH3CH2Cl + H2O
(b) Why is allyl chloride more reactive than vinyl chloride towards nucleophilic substitution reaction?
20 (a) Give one example of
(i)
Natural polymer
(ii)
Chain growth polymer
(b) What is monomer of Neoprene?
© What is meant by vulcanization of rubber?
21. (i) Name a reagent used for purification of Nickel.
(ii) What is the principle of liquation?
(iii)Why are sulphide ores converted into oxide ores before reduction?
22 (a) Why is O-O bond weaker than S-S bond?
(b)Why is F2 better oxidizing agent than Cl2?
© Why OF6 does not exist?
23. Sachin took his father for medical check up. He told his doctor about the symptoms like increase in apetite,
excessive thirst, frequent urination, feeling tired, depressed and eye sight problem.Doctor advised him to take
balanced diet, no sugar and do walking daily.
After reading the passage, answer the following questions:
(i) What values are associated with Sachin?
(ii) From which disease Sachin’s father is suffering?
(iii) Name two artificial sweetning agents which can be used instead of sugar.
(iv) Why should Sachin’s father take balanced diet and walk daily?
24. (a) What will happen to cell if it is placed in hypertonic solution?
(b) The elevation in boiling point of 0.1 molal solution of ‘X’ in water is 0.1536 0C. What conclusion do you draw
about molecular state of ‘X’ [Kb =0.512 K kg mol-1
© For which of the following, the Van’t Hoff factor cannot be greater than unity?
K4[Fe(CN)6], AlCl3, NH2CONH2, KNO3
(d) Why is osmotic pressure of 1M NaCl higher than 1M glucose solution?
Or
(i)
I M NaNO3 solution has density 1.25 g cm-3. Calculate its molality.
(ii) Can we separate azeotropes by fractional distillation? Give reason.
(iii) What type of interaction exists between alcohol and water?
(iv) What is the value of ‘I’ for Na2SO4 * 10 H2O
25. (a) Write equations for the following reactions:
(i) Hell Volhard Zelinsky reaction
(ii) Decarboxylation
(iiI) Crossed aldol condensation
(b) An organic compound (A) having molecular formula C 3H8O on treatment with Cu at 573 K gives ‘B’ which
does not reduce Tollens’ reagent but gives yellow ppt. with I2 and NaOH. Identify ‘A’ and ‘B’ and write chemical
equations for the reactions.
Or
(a) Complete the following reactions :
OH(i)
C6H5CHO + CH3CHO
298 K
H+
(ii) CH3CHO + CH3NH2
(i)O3
(iii) CH3
C=CH
CH3
(ii)Zn/ H2
CH3
(b) Distinguish between following compounds by suitable chemical test
(i) Methanol and ethanol
(ii)
Phenol and Benzyl alcohol
26. (a) What is structure of PCl5 in solid state?
(b) Why are all P- Cl bonds in PCl5 not equivalent?
© Complete the following reactions:
(i) PbS + O3→
(ii) KI + O3 + H2O→
(iii) H3PO3
Heat
Or
(a) Draw the structure of the following:
(i)
IF5
(ii)
XeO3
(b) Why does HNO3 become yellow on long standing?
(c) How will you test the presence of SO2?
(d) Why is N2 less reactive at room temperature?
(e) Why is white phosphorus stored under water?
Marking Scheme
1. AgBr
2. CH2=CH-C≡CH + HCl → CH2=CH-C=CH2
(1)
(1)
Cl
3.
CHO
--OH
(1)
4. CH3CH2CH2CH2OH< CH3CH2CH2OH< CH3CH2OH< CH3OH
(1)
5. It is a process in which both adsorption and absorption take place. (1)
6. Molar conductivity of a strong electrolyte does not increase on dilution
because the number of ions does not increase, only mobility of ions
increases on dilution. In case of weak electrolyte, both no. of ions and
mobility of ions increase on dilution, so molar conductivity increases
appreciably.
(2)
Or
Here n=1, k= 10
(1/2)
0
E cell= (0.0591/n) log Kc
(1/2)
0
Solving we get E cell= 0.0591V
(1)
7. For two correct differences.
(2)
8. (i) Glucose is reducing sugar and sucrose is non-reducing sugar.
(1)
(ii)For correct difference.
(1)
9. Those catalysts which catalyse biochemical reactions are called
biocatalysts. Any correct example.
(1+1)
10. (a) Gluconic acid is formed. Correct Equation.
(1/2 +1/2)
(b)Globular protiens are soluble in water. Fibrous protiens are insoluble in
water.
(1)
11. For each correct conversion.
(1X3)
2+
9
12. (i) Because Cu (3d ) has one unpaired electron, therefore it is
paramagnetic whereas Cu+(3d10) does not have any unpaired electron, so it is
diamagnetic.
(1)
2+
2+
(ii) Due to greater effective nuclear in Fe than Mn due to higher atomic
number
(1)
(iii) For correct structure .
(1)
-3
13. d =2.189 g cm
(3)
Or
(i) Definition and one example
(1+1)
(ii) Schottky defect
(1)
(iii)For correct definition of 13-15 compounds.
(1)
14.(a) For correct equations
(1X2)
(b) It is because phenyl group is electron withdrawing in aniline due to
which electron density on ‘N’ is less in Aniline than cyclohexylamine.
Pi
0
0
15. SO2Cl2 (g) → SO2 (g) +Cl2 (g)
Pi – x
x
x
(1)
PT = Pi – x + x + x = Pi + x
PT – Pi = x
(1)
Here Pi =0.4, PT = 0.7
K = (2.303/t) log (Pi / Pi –x)
Solving we get k = 1.386 x 10-2 s-1
(1)
1/n
16 (i). x/m =k p
Or log x/m = log k + 1/n log p
(1)
(ii)For correct graph.
(1)
(iii)Slope = 1/n , intercept = log k
(1)
2+
5
3+
4
17 (a) It is because Mn (3d ) is more stable than Mn (3d ), whereas Fe3+
(3d5) is more stable than Fe2+ (3d6). Therefore Mn2+ compounds are more stable,
i.e. do not get oxidized to Mn3+ but Fe2+ compounds are readily oxidized to
Fe2+compounds.
(1)
(b) Zn is not a transition metal because neither Zn nor its ions have
incompletely filled d- orbitals.
(1)
2+
5
©Mn (3d ) is the most paramagnetic as it has maximum no. of unpaired
electrons.
(1)
18 (a) Diamminetetraaqua cobalt(III) chloride.
(1)
2
(b) (i) dsp , square planar, diamagnetic
(1)
3
(ii) sp , tetrahedral, paramagnetic
(1)
2
19 (a) it follows SN mechanism.
(1/2)
For correct mechanism.
(1.5)
(b) It is because allyl carbocation is stabilized by resonance whereas
vinyl carbocation is not.
(1)
20 (a) (i) Natural rubber or any.
(0.5)
(ii) Polythene or any.
(0.5)
(b) Chloroprene
(1)
© The process in which natural rubber is heated with sulphur to make it
hard and more elastic.
(1)
21(i) carbon monoxide
(1)
(ii) the impurities have higher melting point than pure metal.
(1)
(iii) because it is easier to reduce oxide ore than sulphide ore.
(1)
22.(a) Due to repulsion between valence electrons of smaller size oxygen atom
than sulphur atom.
(1)
(b)F2 has higher reduction potential than Cl2.
(1)
© Due to absence of d-orbital in oxygen atom.
(1)
23.(i) Sachin is concerned about his father’s health.
(1)
(ii) Diabetes
(1)
(iii) Sucralose, aspartame, alitame.
(iv)Help in increasing metabolic rate and in reducing blood glucose level. (1)
24.(a) The cell will shrink.
(1)
(b) Δ Tb = Kb x m = 0.512 x 0.1 = 0.0512
(1)
Van’t hoff factor (i) =0.1536/0.0512 =3
The solute ‘X’ is a strong electrolyte and dissociates into ions.
(1)
© NH2CONH2 has i=1
(1)
+
(d) because NaCl dissociates into Na and Cl and therefore osmotic pressure of
1 M NaCl is almost double than 1 M glucose as no. of particles is double.
(1)
Or
(i) For correct formula, substitution and getting molality = 0.858 mol/kg (2)
(ii) No because they distill out together and remain unchanged in their
composition.
(1)
(iii) Intermolecular H-bonding.
(1)
(iv) Van’t Hoff factor (i) = 3
(1)
25.(a) For each correct reactions.
(1x3)
(b) A= Propan-2-ol , B = Propan-2 one (acetone)
(1)
For correct equations.
(1)
Or
(a) For completion of all the reactions.
(1x3)
(b) (i) Add I2 and NaOH , Ethanol will give yellow ppt of iodoform, whereas
methanol will not react.
(1)
(ii) Add neutral FeCl3, Phenol will give violet colour. Benzyl alcohol will not
react.
(1)
+
26. (a) [PCl4] [PCl6]
(1)
(b) It is because these bonds are not coplanar. Axial bonds are longer and
weaker than equatorial bonds due to more repulsion.
(1)
© (i) PbS + 4O3→ PbSO4 + 4O2
(1)
(ii) 2KI + O3 + H2O→ 2KOH +O2 + I2
(1)
(iii) 4H3PO3→ 3H3PO4 + PH3
(1)
Or
(a) For correct structures
(1/2x2)
(b) It is because it decomposes to NO2 which imparts yellow colour. (1)
(c) Acidified K2Cr2O7 paper turns green with SO2 gas.
(1)
(d) Due to presence of triple bond which has high bond dissociation energy.
(1)
(e) It has low ignition temperature and may catch fire at room temp. (1)