Chemistry (Theory) 2012-2013 ISC (Commerce) Class 12 Question Paper Solution

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

(zero, first, second, increased, decreased, anode, cathode, active, inactive, potassium cyanide, internal, external, dependent, independent, red, benzoic acid, benzoin, common ion effect, salt hydrolysis, alkali, potassium hydroxide,)

(i) In a galvanic cell, electrons flow from ………. to ……….. through the connecting wires.

(ii) Racemic mixtures are optical …………. because of …………… compensation.

(iii) The half-life period of a …………. order reaction is …………. of the concentration of the reactant.

(iv) Benzaldehyde when treated with an alcoholic solution of ……… forms ………..

(v) The solubility of calcium oxalate is …………. in the presence of ammonium oxalate because of ……… .

The compound which is optically active is:

1-butanol

2-butanol

1-propanol

2-methyl-1-propanol

The salt which will not hydrolyse in aqueous solution is: 

Copper sulphate

Sodium sulphate

Potassium cyanide

Sodium carbonate

Copper has the face centred cubic structure. The coordination number of each ion is:

4

12

14

8

For the reaction 2SO₂ + O₂ ⇌ 2SO₃, the unit of an equilibrium constant is :

L mol^-1

J mol^-1

mol L^-1

[L mol^-1]²

The deficiency of vitamin D causes:

Rickets

Gout

Scurvy

Night blindness.

Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.

Two moles of NH₃ are introduced into the one-litre flask in which it dissociates at high temperature as follows: 2NH₃(g)  ⇌ N₂(g) + 3H₂(g). Determine Kc, if at equilibrium 1 mole of NH₃ remains.

Give a balanced equation for the preparation of salicylaldehyde from phenol.

If the half-life period for a first-order reaction is 69-3 seconds, what is the value of its rate constant?

Define cryoscopic constant. 

Match the following:

Ethylene glycol is used as an antifreeze agent. Calculate the amount of ethylene glycol to be added to 4 kg of water to prevent it from freezing at -6°C. (K_f for H₂O = 1 .85 K mole^-1 kg)

The freezing point of a solution containing 0.3 gms of acetic acid in 30 gms of benzene is lowered by 0.45 K. Calculate the Van’t Hoff factor. (at. wt. of C = 12, H = 1, O = 16, K_f for benzene = 5.12 K kg mole⁻¹). 

When water is added to 0.01M aqueous solution of acetic acid the number of hydrogen ions increases.

When 96500 coulombs of electricity is passed through acidulated water, 5·6 litres of oxygen at s.t.p. is liberated at the anode.

Arrange Ag, Cr and Hg metals in the increasing order of reducing power. Given:

`(E_(Ag^+)^o)/(Ag) = +0.80V`

`(E_(Cr^(+3))^o)/(Cr) = -0.74V`

`(E_(Hg^(+2))^o)/(Hg) = +0.79V`

In a first-order reaction, 10% of the reactant is consumed in 25 minutes  Calculate: 

(i) The half-life of the reaction.
(ii) The time required for completing 17% of the reaction.

A solution of NH₄Cl and NH₄OH acts as a buffer.

Cu is precipitated as CuS while  Zn is not precipitated when H₂S is passed through an acidic solution of Cu(NO₃ )₂  and Zn(NO₃)₂ respectively.

What is Schottky defect in a solid?

A bcc element (atomic mass 65) has a cell edge of 420 pm. Calculate its density in gms/cm³ .

The rate of the reaction`H_2 +I_2 ⇌ 2HI` is  given by:
                       Rate = 1.7 × 10^-19 [H₂] [I₂] at 25°C.
The rate of decomposition of gaseous HI to H₂ and I₂ is given by:
                      Rate = 2.4 × 10^-21 [HI]² at 25°C.
Calculate the equilibrium constant for the formation of HI from H₂ and I₂ at 25°C.

Give Lewis's definition of acids and bases.

 The solubility of Ag₂CrO₄ at 25°C is 8.0 × 10^-5 moles litre^-1. Calculate its solubility product.

Define the molar conductance of a solution. State its unit. How is it related to the specific conductance of a solution? 

Calculate the value of E_cell at 298 K for the following cell:

`(Al)/(Al^(3+)) (0.01M) || Sn^(2+) ((0.015 M))/(Sn)`

`E°  _(Al^(3+))/(AI)= -1.66 " Volt and " E° _(Sn^(2+)) /(Sn) = -0.14` volt

Calculate the degree of hydrolysis of 0.2 (M) sodium acetate solution. 
(Hydrolysis constant of sodium acetate = 5.6 × 10^-10 and ionic product of H₂O = 10^-14 at 25°C).

Explain why high pressure is used in the manufacture of ammonia by Haber's process. Stiite the law or principle used.

Give the IUPAC names of the following coordination compounds:
(i) K₂[Zn(OH)₄]
(ii) [CO(NH₃)₅ (CO₃)] Cl.

For the complex ion [Fe (CN)₆]^3- state: 
(i) The geometry of the ion.
(ii) The magnetic property of the ion.

What type of structural isomers are [Co(NH₃)₅ Br] SO₄ and [Co(NH₃)₅ SO₄]Br? Give a chemical test to distinguish the isomers. 

For the molecule XeF2 :
(i) Draw the structure of the molecule indicating the lone pairs.
(ii) State the hybridization of the central atom.
(iii) State the ge.ometry of the molecule.

Give balanced chemical equations for the following reactions: 
(i) Fluorine treated with a dilute sodium hydroxide solution.
(ii) Hydrogen sulphide treated with concentrated sulphuric acid.
(iii) Potassium iodide treated with acidified potassium pennanganate solution. 

In the extraction of zinc from zinc blende:

(i) Give an equation to show how zinc oxide is converted to zinc.
(ii) How is impure zinc finally electro-refined? 

Explain why:
(i) Transition elements form coloured compounds. 
(ii) Interhalogen compounds are more reactive than their constituent elements.
(iii) Cu⁺ is diamagnetic but Cu²⁺ is paramagnetic. (Z = 29)

Nitrobenzene to benzene diazonium chloride.

Propanoic acid to ethylamine.

Benzoic acid to benzaldehyde.  

Identify the compounds A, B, C, D, E and F:  

Acetamide is heated with bromine and sodium hydroxide solution.

Benzaldehyde is treated with 50% sodium hydroxide solution.

Give one chemical test to distinguish between the following pair of compounds: Acetone and phenol.

Give one chemical test to distinguish between the following pair of compounds: Formic acid and acetic acid.

Name the type of isomerism exhibited by the following pairs of compound:
(1) (C₂H₅)₂NH and CH₃-NH-C₃H₇
(2) 1 – butanol and 2 methyl-1 -propanol.

Name the type of isomerism that the compound with molecular formula C₃H₆O₂ exhibits. Represent the isomers.

Write balanced chemical equations for the following reactions:
Oxalic acid is treated with acidified potassium permanganate solution.

Write balanced chemical equation for the following reaction: 
Benzoic acid is treated with a mixture of concentrated nitric acid and concentrated sulphuric acid.

Write balanced chemical equation for the following reaction:
Methyl magnesium iodide is treated with carbon dioxide and the product hydrolysed in acidic medium.

Write balanced chemical equation for the following reaction:
Ethylacetate is treated with ammonia.

An organic compound [A] having molecular formula C₂H₇N on treatment with nitrous acid gives a compound [B] having molecular formula C₂H₆O. [B] on treatment with an organic compound [C] gives a carboxylic acid [D] and a sweet-smelling compound [E]. Oxidation of [B] with acidified potassium dichromate also gives [D].
(i) Identify [A], [B], [C], [D] and [E].
(ii) Write a balanced chemical equation of [D] with chlorine in the presence of red phosphorus and name the reaction.

Acetamide is amphoteric in nature. Give two equations to support this statement.