GOA BOARD OF SECONDARY AND HIGHER SECONDARY EDUCATION
MODEL QUESTION PAPER
CHEMISTRY XII
Time : 3 hours
Max marks: 70
GENERAL INSTRUCTIONS.
1. All question are compulsory.
2. Answer each question on a fresh page.
3. Figures to the right indicates full marks.
4. There is no overall choice. However internal choice has been provided in 2
sub questions of 2 marks category and 1 sub questions of 3 marks category.
5. Use of calculators is not permitted. However you may ask for mathematical
tables.
Q 1.
(A) Draw a graph to show the effect of catalyst on activation energy. State any two
factors which affect the rate of a reaction.
Write the average rate expression for the reaction.
(3)
N2 (g) + 3H2 (g) → 2NH3 (g)
(B) Calculate the time needed for the reaction of a substance with initial
concentration ‘a’ and following a zero order kinetics to go to completion.
(2)
(C) Which of the two solutions 60g/l of urea (NH2CONH2) and 58.5g/l of sodium
chloride will have a higher osmotic pressure? Justify your answer.
(2)
(D) Explain with a graph how the boiling point of a solution is raised when a nonvolatile solute is added to it.
(2)
(E) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement.
(1)
With increase in temperature ____________________
 The vapour pressure of liquid solvent increases more sharply than frozen
solvent.
 The vapour pressure of liquid solvent and frozen solvent remains the same.
 The vapour pressure of liquid solvent increases but that of the frozen
solvent decreases.
 The vapour pressure of liquid solvent decrease but that of the frozen
solvent increases.
Q 2.
(A) Explain with the help of a graph why the limiting molar conductivity cannot
be determined for a weak electrolyte but can be determined for strong
electrolyte (2)
(B) Given E0 Ag+/Ag = 0.80 V and E0 Fe3+/Fe2+ = 0.70 V
Calculate the molar concentration of Ag+ ions at 298K in the cell formed using
the above electrodes for the same molar concentration of Fe2+ and Fe3+ ions if
the emf of the cell is zero and the standard emf of the cell is 0.1V.
(2)
(C) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement.
(1)
In the lead storage cell __________________
 the cell reaction cannot be reversed by any method.
 the e.m.f. does not depend on the density of H2SO4 solution.
 during charging, SO42- ions are liberated at the anode.
 the spongy lead electrode behaves as negative terminal when current is
drawn from the cell.
(D) Write balanced chemical equations involving the following reactions:
(3)
(1) preparation of sodium chromate from chromite ore.
(2) laboratory method for the preparation of potassium permanganate.
(3) action of acidified KMnO4 on oxalic acid.
(E) ( i ) Explain why transitions elements and their compound show paramagnetic
behaviour.
(1)
( ii ) Write the electronic configuration of Gd ( Z = 64).
(1)
Q 3.
(A) With respect to the group 16 elements answer the following:
(3)
(1) write trends in oxidation states of the group.
(2) write only the name of the structure exhibited by SF4 and SF6.
(3) arrange the hydrides of this group in the increasing order of their thermal
stability.
OR
(A) With respect to the group 18 elements answer the following:
(3)
(1) Write the electronic configuration of the last 2 elements of this group.
(2) Write the balanced chemical equation for the preparation of XeF6 and also
for
the hydrolysis of XeF4.
(B) Answer each of the following with respect to the compounds of group 15
elements:
(2)
(1) write the equation for the reaction of ammonia with Cu2+ ions and explain
why ammonia acts as a Lewis base in the reaction.
(2) orthophosphorous acid is a dibasic acid, while orthophosphoric acid is a
tribasic acid. Explain.
(C) Write only balanced chemical equation for the preparation of chlorine by
Deacon’s process.
(1)
(D) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement:
The following order is not in accordance with the property
stated against it.
(1)
 HI > HBr > HCl > HF ---- acidic property in water.
 I2 < Br2 < Cl2 < F2 ------- oxidising power.
 F2 > Cl2 > Br2 > I2 ------- electronegativity.
 I2 < Br2 < Cl2 < F2 ------- bond dissociation energy.
(E) With respect to metallurgy, answer each of the following questions:
(2)
(1) Write two points indicating the role of cryolite in the metallurgy of
aluminium.
(2) Draw a neatly labelled diagram showing FROTH FLOATATION
PROCESS.
(F) From the following ores-bauxite, malachite, haematite and zinc blende, which
one can be concentrated by magnetic separation method? Give the reason for
your answer.
(1)
Q 4.
(A) Write and name the coordination entity formed in which the central metal
atom has oxidation state +1 and coordination No. 4, when excess of KCN is
added to a solution of copper sulphate.
(2)
(B) [ Fe(H2O)6]3+ is strougly paramagnetic whereas [ Fe(CN)6]3- is weakly
paramagnetic. Explain.
(1)
(C) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement.
The central metal atom is in a state of sp3d2 hybridisation in the complex
species ________________
(1)
 [ CuF6]3 [ Co(NH3)6]3+
3 [Fe(CN)6]
 [Cr(NH3)]3+
(D) Differentiate between Bakelite and polythene with respect to mode of
polymerisation and the monomer used.
(2)
(E) Identify the synthetic rubber that is resistant to vegetable or mineral oil.
(1)
(F) Answer each of the following questions:
(3)
(1) State the function of glycerol in shaving cream.
(2) Name the first effective antibacterial agent and state the active compound
to which it is converted.
(3) Which of the following substance ---- alitame, sucrolose or aspartame is
the most stable at cooking temperature? State its use.
Q 5.
(A) Draw a diagram of p-type semiconductors and label its parts.
The increase in conductivity when silicon is doped with Arsenic is due to the
negatively charged electron. Why?
(2)
(B) Silver crystallises in the fcc lattice, if edge length of the cell is 4.07×10-8 cm
and density is 10.5g.cm-3. Calculate the atomic mass of silver. [NA=6.02×1023]
(2)
(C) Draw a neat labelled diagram to illustrate Tyndall effect. What is the cause of
Tyndall effect?
(2)
(D) (1) Name the two ways by which coagulation of hyophobic sols can be done.
(1)
(2) Why is adsorption an exothermic process?
(1)
OR
(1)Which adsorbs more of carbon monoxide, charcoal lump or charcoal
powder and why?
(1)
(2) H2 gas molecules were adsorbed on the surface of an adsorbent and the
layer was formed to be unimolecular. Name the type of adsorption.
(1)
(E) Name the major product formed when alkyl halide reacts with silver cyanide.
(1)
(F) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement.
(1)
The increasing order of the reactivity of the compound in SN, reaction is
_______




(CH3)2CHCH2Br < CH3CH2CH2CH2Br < CH3CH2CH(Br)CH3 < (CH3)3 CBr.
CH3CH2CH2CH2Br < (CH3)2CHCH2Br < CH3CH2CH(Br)CH3 < (CH3)3 CBr.
(CH3)3 CBr < CH3CH2CH(Br)CH3 < (CH3)2CHCH2Br < CH3CH2CH2CH2Br.
CH3CH2CH(Br)CH3 < (CH3)3 CBr < CH3CH2CH2CH2Br < (CH3)2CHCH2Br.
Q 6.
(A) Write the mechanism for the nuleophilic substitution of an alkyl halide which
involves 100% inversion.
(2)
(B) Write the structural and functional differences between DNA and RNA.
(2)
OR
(B) Differentiate between globular proteins and fibrous proteins with respect to the
polypeptide chain and solubility in water.
(2)
(C) Name the following.
(2)
(1) the polysaccharide that contains β-D-Glucose units.
(2) the linkage holding amino acids in proteins.
(3) deficiency caused due to lack of vitamin B-12
(4) a keto hexose suger.
(D) Write labelled chemical equations for the following.
(2)
(1) reaction of HI on anisole.
(2) acetylation of salicylic acid.
(E) Name the product obtained when 2-butanol is treated with concentrated
sulphuric acid at 443K.
(1)
(F) Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement:
(1)
The structure of the compound that gives a tribromo derivative on treatment
with water is _____________
CH3
CH3


OH
OH
CH3
CH2OH


CH3
Q 7.
(A) A hydrocarbon ‘A’ having molecular formula C7H8 on reacting with chromic
oxide and acetic anhydride, followed by acid hydrolysis gives compound ‘B’
which does not show Fehling’s test compound ‘B’ reacts with acetophenone in
presence of dil. barium hydroxide to give compound ‘C’. Identify compounds
‘A’ , ‘B’and ‘C’ and write the chemical equations for the sequence of
reactions.
(3)
(B) How will you convert
(2)
(1) Acetic acid to methane.
(2) 3-nitrobromobenzene to 3-nitrobenzoic acid.
(C)
Complete the following statement by choosing the correct alternative given
below the statement and REWRITE the completed statement:
In the reaction sequence.
(1)
H

2O
A 
 B H

C 

CH 2  CH  COOH
HCN
‘A’, ‘B’ are ________________
 CH3CHO & CH3CH2COOH
 CH3CHO & CH3 -CH-CN
|
OH
 CH3CHO & CH3 -CH-COOH
|
OH
 CH3COCH3 & CH3 -CH-COOH
|
OH
(D) Arrange the following compounds -- (CH3)3NH , (CH3)2NH and CH3NH2. in
the increasing order of their basicity in aqueous medium, giving reasons.
(2)
(E) Compound ‘A’ with molecular formula C2H7N reacts with benzene sulphonyl
chloride to give a compound soluble in NaOH.
Write the chemical equations for the reactions and give the IUPAC name of
the compound ‘A’.
(1)
(F) Write the chemical equation when benzene diazonium chloride reacts with
phenol in the presence of a base.
(1)
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