Plus Two Chemistry Model Question Paper 5

Kerala Plus Two Chemistry Model Question Paper 5

Time: 2 Hours
Cool off time: 15 Minutes
Maximum: 60 Scores

General Instructions to candidates

• There is a ‘cool off time’ of 15 minutes in addition to the writing time of 2 hrs.
• Use the ‘cool off time’ to get familiar with the questions and to plan your answers.
• Read questions carefully before you answering.
• Read the instructions carefully.
• Calculations, figures, and graphs should be shown in the answer sheet itself.
• Malayalam version of the questions is also provided.
• Give equations wherever necessary.
• Electronic devices except non-programmable calculators are not allowed in the Examination Hall.

Questions from 1 to 7 carry 1 score. Answer any 6 questions.

Question 1:
The edge length and axial angles of a unit cell are a = b = c and α = β = γ = 90° respectively. Identify the type of Crystal System.

Question 2:
Name the polymer used for non-stick surface coated utensils

Question 3:
Which of the following forms colored compounds.

i. Sc³⁺
ii. Cr²⁺
iii. Zn³⁺
iv. Cu⁺
[Atomic number Sc – 21, Cr – 24, Zn – 30, Cu – 29]

Question 4:
The rate expression of a reaction is Rate = K [A]^{\(\frac { 1 }{ 2 }\)} [B]^{\(\frac { 1 }{ 2 }\)}. Calculate its overall order.

Question 5:
Among the following amines, identify the one that does not reach with Hinsberg reagent

i. C₂H₅NH₂
ii. (CH₃)₂NH
iii. (C₂H₅)₂NH
iv. (CH₃)₃N

Question 6:
The Carbohydrate, that is known as ‘animals starch’ is ………

Question 7:
Name the class of drug used for the treatment of stress and mental diseases.

Questions from 8 to 20 carry 2 score. Answer any 10 questions.

Question 8:
Write the names and structure of the monomers of the polymer Buna – S

Question 9:
Calculate the packing efficiency in body centred cubic structure.
[Given that r = \(\frac { \sqrt { 3 } }{ 2 }\)a, Where ‘r’ is the radius of sphere and ‘a’ is the edge length of unit cell]

Question 10:
Write one method for the preparation of sulphur dioxide. How is its presence detected?

Question 11:
Write the IUPAC names of following com-pounds.

(a) K₃[Fe(CN)₆]
(b) CO[Cl₂(en)₂Cl

Question 12:
Define Van’t Hoff factor ‘i’. What would be the value of ‘i’ for a dilute solution of K₂SO₄ in water?

Question 13:
By taking ethyl bromide as starting material, prepare ethyl iodide and ethyl fluoride.

Question 14:
Write the complete reaction representing the disproportionation of benzaldehyde.

Question 15:
Vapour pressure of water at 293 K is 17.535 mm Hg. Calculate the vapour pressure of water at 293 K when 25 g of glucose is dissolved in 450 g of water.

Question 16:
Name the products of hydrolysis of sucrose is not a reducing sugar.

Question 17:
Tetiary buty bromide react with aqueous NaOH to give tertiary butyl alcohol proceeds via S_N1 reaction. Write the mechanism of the reaction.

Question 18:
Give the structures of A and B in the following reaction.

Question 19:
Match the following

Question 20:
Write a simple chemical test to distinguish ethanal from propanone.

Questions from 21 to 29 carry 3 score. Answer any 6 questions.

Question 21:
The resistance of a 0.5 M solution of an electrolyte enclosed between two platinum electrode 1.5 cm apart and having an area of 2.0 cm² was found to be 30Ω. Calculate the molar conductivity of the solution.

Question 22:
write notes on different allotropic forms of phosphorous.

Question 23:
Integrated rate equation for a first order reaction.

a. Derive an expression for half life of first order reaction

b. Find the half life of first order reaction having rate constant K = 5.5 x 10^-14S^-1

Question 24:
What are adsorption isotherms? Write the Freundlich absorption isotherm equation and plot agraph based on it.

Question 25:
Describes the steps involved in the manufacture of sulphuric acid by contact process.

Question 26:
Differentiate ferrimagnetism from paramagnetism and predicts the change that takes place to ferrimagnetic substances on heating.

Question 27:
a. Draw the structure of dichromate ion.
b. How can dichromate ion be converted to chromate ion?
c. Write examples for the oxidising action of potassium dichromate in acidic medium.

Question 28:
Explain the following
a. Hydraulic washings
b. zone refining
c. Roasting of ores

Question 29:
Describe the following reactions.
a. Aldol condensation
b. Etard reaction
c. Rosenmund reduction

Questions from 30 to 33 carry 4 score. Answer any 3 questions.

Question 30:
Write chemical equations for the conversion of phenol to acetyl salicylic acid (aspirin)

Question 31:
With the help of diagram describe the construction and working of a fuel cell using H₂, and O₂. What are the advantages of fuel cell over conventional cells.

Question 32:
Sketch the Crystal field splittng of d-orbit- als of the Central metal ion in [CoF₆]^3-. Also write the electronic configuration of central metal ion and predict its magnetic behaviour based on crystal field theory.

Question 33:
Give the structure and IUPAC names of the products formed on the following reactions
a. Hydration of propene in the presence of dilute sulphuric acid.
b. Reaction of methanal with methyl mag-nesium bromide followed by hydrolysis.

Answers

Answer 1:
Cubic

Answer 2:
Teflon

Answer 3:
Cr²⁺(4 unpaired d electrons)

Answer 4:
Order of the reaction = \(\frac { 1 }{ 2 }\) + \(\frac { 3 }{ 2 }\) = \(\frac { 4 }{ 2 }\) = 2

Answer 5:
iv

Answer 6:
Glycogen

Answer 7:
Tranquilizers

Answer 8:

Answer 9:
In bcc

Answer 10:
Sulphur dioxide is formed together with a little (6 – 8%) sulphur trioxide when sul¬phur is burnt in air or oxygen.

S(s) + O₂(g) → SO₂(g)

SO₂ is a colourless and pungent smell gas It can detected by using potassium permag- nate solution when SO₂ is passed through an acidified potassium permanganate solu¬tion, then it decolonises the solution as it reduces MnO₄^– ions to Mn²⁺ ions. SO₂ give out suffocating smell which indicates its presence

Answer 11:
a. Potassium hexacyanoferrate (III).
b. Dichloridobis (ethane -1,2- diamine) cobalt (III) chloride.

Answer 12:
Vant Hoff factor is the ratio of the observed college five property to the normal colligative property
i = \(\frac { observed collegative property }{ Theoretical collegative property }\)
Dilute solution of K₂SO₄( would dissociate into two K⁺ ions and a sulphate ion.
K₂SO₄ → 2K⁺ + SO₄^2-
The Van’t hoff factor for a dilute solution of K₂SO₄ is 3.

Answer 13:

Answer 14:
Cannizzaro reaction which do not have an a-hydrogen atom, undergo self oxidation and reduction (disproportionation) reaction on heating with concetrated alkali. In this reaction, one molecule of the aldehyde is reduced to alcohol while another is oxidised to carboxylic acid salt.

Answer 15:

Answer 16:
Hydrolysis of sucrose gives equimolar mixture of D – (+) – glucose and D – (-) fractose.

Sucrose ¡s non-reducing sugar because aldehyde group of glucose and keto group of fractose are not fuce and involved in glycosidic bond formation.

Answer 17:
The reaction between tert-butyl bromide and hydroxide ion yields tert-butyl alcohol and follows the first of order kinetics, i.e, the rate of reaction depends upon the concetration of only one reactant, which is tert butyl bromide.
(CH₃)₃ CBr + NaOH → (CH₃)₃COH + NaBr
If occurs in two steps
Step I : The polarised C-Br bond under¬goes slow clearage to produce a carbocation and a bromide ion. The carbocation thus formed is then attacked by nucleophile in step II to complete the substitution reaction.

Answer 18:

Answer 19:
a. Antiseptic                                  –            bithional
b. Artificial sweetners                 –            Saccharin
c. Soap                                            –            Sodium stearate
d. Vitamin C                                  –           ascorbic acid

Answer 20:
Ethanal give silver mirror with tollens reagent where as propanone will not react

Answer 21:

Answer 22:
There are 3 allotropic forms of phosphorus.

White phosphrous:

• Translucent white waxy solid
•  Garlic smell
• Poisonous
•  Less stable due to angle strain. (60° PPP bond angle)
• Readily catches fire in air.
  

Red phosphorus:

• Iron grey lustrous powder
• Odourless
• Non-poisonous
•  More stable than white phosphorus
  

Black phosphorus:
It has two forms α black phosphorus and β black phosphorus. When white phosphorus is heated under high pressure at 473 K β black phosphorus is formed.

Answer 23:

Answer 24:
The relationship between extent of adsorption and pressure of the gas at constant temperature is called adsorption isotherm and is given by
\(\frac { x }{ m }\) = kp ^{\(\frac { 1 }{ n }\)} (n> 1)
Freundlich Adsorption Isotherm
where x = mass of gas adsorbed on ‘m’ mass of the adsorbent at p pressure, k, n are constants.

Observations:

• At low pressure \(\frac { x }{ m }\) ∝ p (graph is linear).
•  At high pressure \(\frac { x }{ m }\) is independent of p (graph – straight line).
• At intermediate pressure \(\frac { x }{ m }\) = kp^{\(\frac { 1 }{ n }\)}

Taking logarithm on both sides. We get

In case of a solution, the isotherm takes the form, x = k(C)^{\(\frac { 1 }{ n }\)}

Answer 25:
H₂SO₄ is manufactural by the contact process which involves three steps
(1) Burning of sulphur or sulphide uses in air to generate SO₂
S + O₂ → SO₂

(2) Conversion of SO₂ to SO₃ by the reaction with oxygen in the presence of a catalyst
2SO₂(g) + O₂(g) \(\underrightarrow { { V }_{ 2 }{ O }_{ 5 } }\) 2SO₃(g)
Absorption of SO₃in H₂SO₄ to give oleum (H₂S₂O₇)
SO₃ + H₂SO₄(dil) → H₂S₂O₇ (Oleum)
Oleum is diluted with water to form H2S04
H₂S₂O₇+ H₂O → 2H₂SO₄

Answer 26:
Ferrimagnetism is observed when the magnetic moments of the domains in the sub-stances are aligned in parallel and antiparallel directions in unusual numbers. They are weakly attracted by magnetic field as compared to ferromagnetic substances.
Paramagnetic substances are weakly attracted by a magnetic field. They are magnetised in a magnetic field in the same direction. They lose their magnetism in they absence of magnetic field. Paramagnetism is due to presence of one or more unpaired electrone which are attracted by the magnetic field.
Ferrimagnetic substance lose ferrimagnetism on heating and become paramagnetic.

Answer 27:

b. The chromate and dichromateions are interconvertible in aqueous solution depending upon the pH of the solution

Acidified potassium dichromate will oxidise iodides to iodine sulphides to sulphur.
tin (II) to tin (iv) and iron (ii) salt to iron (iii)

Answer 28:
a. It is also called gravity separation. It is based on the difference in densities (gravities) of ore and the gangue. Ore is washed with stream of water so that light impurities are washed away, eg., haematite.
b. It is based on the principle that the im-purities are more soluble in the melt than in the solid state of metal.

The impure metal is heated with the help of a circular mobile heater at one end. This results in the formation of a molten zone. As the heater is moved along the rod, pure metal crystallises out of the melt and impurities pass onto the adjacent molten zone. This is reimpurities at one end of the rod is cut off and discarded.

•  Metals like Si, Ge, Ga, B etc are refined by this method (semi-conductors and metals of high purity).

c. It is a process in which an ore is heated in regular supply of air at a temperature below the melting point of the metal so as to convert the give ore into oxide ore.
2ZnS + 3O₂ → 2ZnO + 2SO₂

Answer 29:
a. Aldehydes and ketones having at least one α hydrogen undergo a reaction in the presence of dilute alkali as catalyst to form β – hydroxy aldehydes (aldol) or β hydroxy ketones (ketol), respectively. This is known as aldol reaction. The aldol and ketol readily lose water to give α, β – unsaturated carbonyl compounds which are aldol condensation products and the reaction is called aldol condensation

b. Strong oxidising agents oxidise tolerene and derivatives to benzoic acids. How-ever, it is possible to stop the oxidation at the aldehyde stage with suitable reagents that convert the muthyl group to an inter¬mediate. Chromy chloride (CrO₂Cl₂) oxidise methyl group to a chromium complex, which on hydrolysis gives corresponding benzaldehyde.

This reaction is called Etard reaction

c. Acyl chloride (acid chloride) is hydrogenated over catalyst, palladium on burium sulphate. This reaction is called Rosenmund reduction.

Answer 30:
Kolbe’s reaction : Phenoxide ion generated by treating phenol with sodium hydroxide is even more reactive than phenol towards electrophilic aromatic substitution. Hence if undergoes electrophilic substitution with CO₂, a weak electrophite. Ortho hydroxybenzoic acid is formed as the main reaction product.

Answer 31:
Fuel Cells: They produce electrical energy directly from the combustion of fuels such as hydrogen. carbon monoxide or methane. It is a Galvanic cell.

The electrode reactions of the most popular fuel cell H₂– O₂ cell is given below:

Advantages:

• PoHution-free.
•  High efficiency (70%).
• Continuous source of energy if gas supply ‘s maintained.
•  The electrodes used in fuel cells are not affected during its working.

Answer 32:
[C0F₆]³Here cobalt is in the +3 oxidation state.

But F^– is a weak ligand. So pairing does not take place. Hence in metal ion under goes sp³d² hybridisation. There are four unpaired electrons present, therefore the complex is paramagnetic.

Answer 33:
a. When hydration of propene in the presence of dilute sulphuric acid. If gives


The grignard reagents (R-Mg -X) react with compounds containing \(\begin{matrix} | \\ C \\ | \end{matrix}\) = o to form addition compounds, which on hydrolysis with dil acid give the corresponding alcohols.Methanal react with grignai reagent to give a primary alcohol.

Plus Two Chemistry Previous Year Question Papers and Answers