ISC 12th Chemistry Sample Paper-1



Paper – 1 (THEORY)


Time: 3 Hours

General Instruction:

(Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time)

  • Answer all questions in Part I and six questions from Part II, choosing two questions from Section A, two from Section B and two from Section C.
  • All working, including rough work, should be done on the same sheet as, and adjacent to, the rest of the answer.
  • The intended marks for questions or parts of questions are given in brackets [ ].
  • Balanced equations must be given wherever possible and diagrams where they are helpful.
  • When solving numerical problems, all essential working must be shown.
  • In working out problems use the following data: Gas Constant $R=1.987 mathrm{cal} mathrm{deg}^{-1} mathrm{~mol}^{-1}=8.314 mathrm{JK}^{1} mathrm{~mol}^{-1}=0.0821 mathrm{dm}^{3} mathrm{~atm} mathrm{~K}^{1} mathrm{~mol}^{-1}$ $1 l mathrm{~atm}=1 mathrm{dm}^{3} mathrm{~atm}=101.3 mathrm{~J} .1$ Farday $=96500 mathrm{Coulombs} .$



Answer all questions (5 marks each)


Question 1

1. Fill in the blanks by choosing the appropriate word/words from those given in brackets:

(electron, proton, neutron, decreases, increasing, lowering, one, two, acidic, basic, anion, cation, paramagnetic, Lewis acid, Lewis base, carbonic acid, sulphurous acid, sulphuric acid, ammonium carbonate, sodium bicarbonate, six, increases)


(i) A positive catalyst____________ the rate of a reaction by__________ the activation energy.

(ii) Human blood is a buffer solution of_________ and______________.

(iii) $mathrm{BF}_{3}$ is a___________ since it is an_______________ deficient molecule.

(iv) Oxygen is______________ due to the presence of_____________ unpaired electrons.

(v) A solution of $mathrm{FeCl}_{3}$ is___________ due to_____________ hydrolysis.


2. Complete the following statements by selecting the correct alternative from the choices given:

(i) $left[mathrm{Co}left(mathrm{NH}_{3}right)_{5} mathrm{Br}right] mathrm{SO}_{4}$ and $left[mathrm{Co}left(mathrm{NH}_{3}right)_{5} mathrm{SO}_{4}right] mathrm{Br}$ exhibit

(a) Coordination isomerism.        (b) Ionisation isomerism.

(c) Hydrate isomerism.                  (d) Geometrical isomerism.

(ii) Cannizzaros’ reaction is given by:

(a) Formaldehyde.                           (b) Acetaldehyde.

(c) Acetone.                                        (d) Ethanol.

(iii) Out of the following solutions, the one having the highest boiling point will be:

(a) $0.01 mathrm{M} mathrm{Na}_{2} mathrm{SO}_{4}$.

(b) $0.01 mathrm{M} mathrm{KNO}_{3}$.

(c) $quad 0.01 mathrm{M}$ Urea.

(d) $quad 0.01 mathrm{M}$ Glucose.

(iv) The bond angle of water is:

(a) $quad 90^{circ}$                  (b) $105^{circ}$

(c) $quad 107.3^{circ}$            (d) $quad 120^{circ}$

(v) The co-ordination number of each ion in copper crystals is:

(a) 4                                                     (b) 12

(c) 14                                                   (d) 8


3. Answer the following questions:

(i) The depression of freezing point caused by a $1 mathrm{M} mathrm{NaCl}$ solution is $0.0123^{circ} mathrm{C}$. What will be the depression of freezing point caused by a $1 mathrm{M}$ glucose solution?

(ii) What happens to the $mathrm{pH}$ of a solution containing equimolar amount of acetic acid and sodium acetate when a few drops of dilute $mathrm{HCl}$ is added? Give reason.

(iii) Express the relationship between molar conductivity and specific conductivity of a solution. What is the unit of molar conductivity?

(iv) Give the electrode reactions of the galvanic cell in which the reaction $mathrm{Zn}(mathrm{s})+2 mathrm{Ag}^{+}(mathrm{aq}) rightarrow mathrm{Zn}^{+2}(mathrm{aq})+2 mathrm{Ag}(mathrm{s})$ takes place.

(v) How is the free energy change related to the enthalpy and entropy change of a substance?


4. Match the followings:

(i) Buffer solution

(a) Co-ordinate bond

(ii) Co-ordination compounds

(b) Raoult’s Law

(iii) Dilute solution

(c) Warner’s Theory

(iv) Ammonium ion

(d) Faraday’s Law

(v) Electrolysis

(e) Henderson’s Equation



Answer six questions choosing two from Section A, two from Section B and two from Section C



Answer any two questions


Question 2

(Part (a) carry 3 marks each part (b) carry 2 marks each)

(a) (i) The vapour pressure of pure benzene at a certain temperature is $640 mathrm{~mm} mathrm{Hg}$. When a non-volatile and non-electrolyte solid weighing $2.175 mathrm{~g}$ is added to $39.0 mathrm{~g}$ of benzene, the vapour pressure of the solution is $600 mathrm{~mm} mathrm{Hg}$. What is the molecular mass of the solid substance?

(ii) Calculate the standard enthalpy change for a reaction $mathrm{CO}_{2}(mathrm{~g})+mathrm{H}_{2}(mathrm{~g}) rightarrow mathrm{CO}(mathrm{g})+mathrm{H}_{2} mathrm{O}(mathrm{g}) .$ Given that

$Delta H_{f}^{circ}$ for $mathrm{CO}_{2}(g), mathrm{CO}(mathrm{g})$ and $mathrm{H}_{2} mathrm{O}_{(g)}$ are $-393.5,-110.5$, and $-244.8 mathrm{KJ} mathrm{mol}^{-1}$


(b) Give reasons for the following:

(i) A solution of copper sulphate is acidic in nature.

(ii) The boiling point of $mathrm{p}$-nitrophenol is more than that of o- nitrophenol.


Question 3

(a) (i) An element crystallizes in a structure having F.C.C. unit cell of an edge $200 mathrm{pm}$. Calculate its density if $200 mathrm{~g}$ of this element contains $24 times 10^{23}$ atoms.

(ii) Draw the electron dot structure of perchloric acid clearly distinguishing between the electrons of each atom.

(b) (i) What is the activation energy of a reaction? How is the rate constant of a reaction related to the activation energy? How can activation energy be calculated from this relationship?

(ii) Consider the following data for the reaction $mathrm{A}+mathrm{B} rightarrow$ Products.

$begin{array}{ccc}text { Conc. of A } & text { Conc. of B } & text { Initial rate } \ left(operatorname{mol} l^{-1}right) & left(operatorname{mol} l^{-1}right) & left(operatorname{mol} l^{-1} mathrm{~S}^{-1}right) \ 0.1 & 0.1 & 4.0 times 10^{-4} \ 0.2 & 0.2 & 1.6 times 10^{-3} \ 0.5 & 0.1 & 1.0 times 10^{-2} \ 0.5 & 0.5 & 1.0 times 10^{-2}end{array}$


(1) The order with respect to A and B for the reaction.

(2) The rate constant of the reaction


Question 4

(a) (i) What is the type of hybridization in $mathrm{PCl}_{5}$ molecule? Explain why $mathrm{PCl}_{5}$ is very reactive in nature.

(ii) If $100 mathrm{ml}$. of $0.1 mathrm{M} mathrm{CH}_{3}
mathrm{COOH}$ is mixed with $200 mathrm{ml}$ of $0.5 mathrm{M} mathrm{CH}_{3} mathrm{COONa}$, what

will be the $mathrm{pH}$ of the resulting mixture?

(b) Give reasons why:

(i) Aluminium trichloride exists as a dimer.

(ii) When $mathrm{H}_{2} mathrm{~S}$ is passed through a solution of acidified copper nitrate and zinc nitrate, only copper is precipitated as sulphide.



Answer any two questions


Question 5

(a) Explain how fluorine is prepared by the electrolysis of potassium hydrogen fluoride.

(b) Give balanced equations for each of the following reactions:

(i) Fluorine and dilute NaOH.

(ii) Ozone and aqueous potassium oxide.


Question 6

(a) Name the following compounds according to I.U.P.A.C. rules:

(i) $left[mathrm{Co}left(mathrm{NH}_{3}right)_{6}right] mathrm{Cl}_{3}$

(ii) $mathrm{K}left[mathrm{Pt} mathrm{Cl}_{3}left(mathrm{NH}_{3}right)right]$

(b) Explain why an aqueous solution of potassium hexcyanoferrate(II) does not give a test for ferrous ion.

(c) Draw the geometrical isomers of the compound $left[mathrm{Co}left(mathrm{NH}_{3}right)_{2} mathrm{Cl}_{2}right]$

(d) Write the formula of potassium trioxalatoferrate (III).


Question 7

(a) Write the steps involved in the preparation of potassium dichromate from chromite ore.

(b) Explain why transition metals form many co-ordination complexes.


Answer any two questions


Question 8

(a) How can the following conversions be brought about?

(i) Methyl amine to ethylamine.

(ii) Propanol to isopropyl alcohol.

(iii) Acetaldehyde to Acetone.

(b) Name the organic compounds which have the same molecular formula $mathrm{C}_{2} mathrm{H}_{6} mathrm{O}$. Write the reactions of these two compounds with $mathrm{PCl}_{5}$.

(c) An alkyl halide having the molecular formula $mathrm{C}_{4} mathrm{H}_{9} mathrm{Cl}$ is optically active. What is its structural formula?


Question 9

(a) Identify the compounds A, B, C and D.

$mathrm{CH}_{3} mathrm{COOH} stackrel{mathrm{LiAIH}_{4}}{longrightarrow} mathrm{A} stackrel{text { red } P, I_{2}}{longrightarrow} mathrm{B} stackrel{mathrm{Alc} . mathrm{KCN}}{longrightarrow} mathrm{C} stackrel{mathrm{H}^{+}, mathrm{H}_{2} mathrm{O}}{longrightarrow} mathrm{D}$

(b) Give one good chemical test to distinguish between the following pairs of compounds:

(i) Benzoic acid and phenol.

(ii) Formaldehyde and Acetaldehyde.

(c) Fill in the blanks and name the following reactions.

(i) $mathrm{C}_{6} mathrm{H}_{5} mathrm{NH}_{2}+mathrm{CHCl}_{3}+3 mathrm{KOH}_{(text {alc. })} stackrel{Delta}{longrightarrow}+mathrm{KCl}+3 mathrm{H}_{2} mathrm{O}$

(ii) $mathrm{C}_{6} mathrm{H}_{5} mathrm{COCl}+mathrm{H}_{2} stackrel{mathrm{Pd} / mathrm{BaSO}_{4}}{longrightarrow}+mathrm{HCl}$

(iii) $+C_{6} H_{5} C O C l stackrel{O H^{-}}{longrightarrow}+H C l$

(d) Give reasons for the following:

(i) Phenol is acidic but ethanol is not.

(ii) Acetaldehyde does not give Cannizzaro’s reaction but formaldehyde and benzaldehyde give the reaction.


Question 10

(a) What are proteins? How are they formed? What is the primary structure of proteins?

(b) Give the monomers of:

(i) Bakelite.

(ii) Nylon – 66.

(c) An organic compound (A) on treatment with acetic acid in the pre
sence of Sulphuric acid produces an ester (B). (A) on mild oxidation gives (C). (C) reduces Tollen’s reagent to give silver mirror and (D). (D) on reacting with Phosphorous pentachloride followed by ammonia gives (E). (E) on dehydration produces methyl cyanide. Identify (A), (B), (C), (D) and (E) and write the relevant reactions.

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