Model Paper-2
Chemistry
CBSE (2001)

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Q 16. For a reaction 3A products, it is found that rate of reaction doubles if concentration of A is increased four times ,calculate order of reaction? (2 marks)

Ans.
Rate = K [Reactant]n , If concentration of reactant =a
& Rate = r₁
and When the concentration of reactant is = 4a, rate =2r₁
r₁ =K[a]ⁿ ----------------->(1)
and, 2r₁ =k[4a]ⁿ------------------->(2)

Dividing (1) by (2)
1 /2 = [1 /4] Therefore , n= 1 /2 = order of reaction is 0.5

Q 17.What happens when: - (2 marks)



Ans.17

Q 18. Write the chemical name of following structure: - (2 marks)


(ii)


Ans.
(i) DDT ( Dichlor diphenyl trichloro ethane)
(ii) 1,3,5 Trimethyl benzene (Mesitylene)

Q 19.Explain: -
a) Cannizzaro's reaction
b) Kolbe's electrolysis
c)Williamson's Synthesis.(2 marks)

Ans.(a) Cannizzaro's reaction: -Aldehydes which does not contain any a-hydrogen atom (HCHO, C₆H₅CHO) undergo self-oxidation and reduction reaction on treatment with concentrated alkali. In this one molecule of aldehyde is reduced to alcohol and other oxidised to the acid. Thus a mixture containing an alcohol and a salt of carboxylic acid is formed. This is Cannizzaro's reaction.

(b) Kolbe's reaction; -When an alkali metal salt of carboxylic acid is electrolysed, then decarboxylation occurs at the anode. This is known as Kolbe's electrolysis.

c)Willimson's synthesis: - When an alkyl halide is treated with sodium alkoxide prepared from sodium and alcohol, a nucleophilic replacement of halogen atom by alkoxide group takes place. This is known as Williamson's Synthesis.

2R'-OH + 2Na 2R'-O-Na+ + H₂

R-X + R'O-Na+ R-O-R' + NaX

This reaction is used for preparation of both symmetrical and unsymmetrical ethers.

Q 20) What happens when: - (2 marks)
a) A solution of sodium acetate is electrolysed.
b) Ethyl alcohol is heated with conc. H2SO4.
c) Acetaldehyde is warmed with NaOH.(mark-2)



Q 21) What is an antibiotic? Give the name of the first antibiotic.
(2 marks)

Ans - "Antibiotic is defined as a chemical substance produced by micro-organisms that can inhibit the growth or even destroy other micro-organism".
Penicillin is the 1st known antibiotic discovered by Alexander Fleming.

Q 22) What happen when: -
a) ZnSO₄ reacts with NaOH solution
b) ZnSO₄ reacts with NH₄OH solution
c) Mg(NO₃)₂ reacts with NH₄OH solution.(2 marks)

Ans.
a) ZnSO₄ +2 NaOH Na₂SO₄ + Zn(OH)₂
b)ZnSO₄ + 2NH₄OH Zn(OH)₂ + (NH₄)₂SO₄
c) Mg (NO₃)₂ + 2NH₄OH Mg(OH)₂ + 2 NH₄NO₃

Q 23 )A potassium salt of ternary acid of Molybdenum (at. Mass= 96) has the formula K₂MoO_n. When an acidified solution of K₂MoO_n is electrolysed between Pt electrodes, O₂ gas liberates corresponding to a volume of 0.121 at STP and 0.3454 gm of Mo is deposited. Find the formula of salt. (3 marks)

Ans. No. of Faraday passed = No. of gm eq. Of O₂ = gm eq. Of Mo
= 4F = 1 mole of O₂
= gm eq. Of O₂ = 4 X 0.121 / 22.4 = 0.026
= gm eq. Of Mo = 0.026
g /m= gm eq. Of Mo
= 0.0215=0.3454 / 96 /x
= x =6
M_o^x+ + 6e M_o
= Oxidation state of Mo = 6
In K₂MoOn, we have 2(+1) + 6 + n(-2) =0
= n=4
= molecular formula is K₂MoO₄

Q 24) How you will distinguish between: -
(i) Acetaldehyde & Propanone
(ii) Formic acid & Acetic acid (2 marks)

Ans.

Formic acid	Acetic acid
1. Reacts with Tollen's reagent to form silver mirror 2.Formic acids reacts with chlorine to form CO2 & HClHCOOH + Cl2 CO2 + HCl	1. No reaction 2. it gives Chloroacetate acid CH3COOH + Cl2 CH2ClCOOH

Q 25) What is a fertilizer? Name three important fertilizers. (2 marks)

Ans. Plants needs several elements for their growth. The three most elements for the plants are Nitrogen (for rapid growth & good protein contents), phosphorus (for root growth) & potassium ( for flowering & strength of stalks) .Compound of nitrogen, phosphorus & Potassium, which are put into soil to increase the agriculture production are called Chemical fertilizer .Three important fertilizer are Urea, superphosphates of lime & Calcium superphosphate nitrate.

Q 26)Write down the structural formula of glucose & Fructose & indicate the functional group?(2 marks)

Ans.


Q 27)Complete the following reaction: - (2 marks)
₄Be⁹ + ₂He⁴ ₆C + n
₁₁Na²³ + ₁H² Mg²³ + ₀n

₃Li⁷ + ₁H^{2 8}Li + H¹

Ans.
₄Be⁹ + ₂He⁴ ₆C¹² + ₀n¹
₁₁Na²³ + ₁H² ₁₂Mg²⁴ + ₀n¹
₃Li⁷ + ₁H² ₈Li₃ + ₁H¹

Q 25)What will be the sequence of bases on DNA molecules synthesised on the following strand of chromose? ATTCCGGA (2 marks)

Ans. The sequence is as follows:
TAAGGCCT

Q 26)Mention the geometrical shapes attained by the following types of hybrid orbital: a) SP³ b) dsp³ c) d²sp³ (3 marks)

Ans. a) Tetrahedron b) Triangularbipyramid c)Octahedron

Q 27)Illustrate with an example each of the following :
a) Geometrical isomerism
b) Optical isomerism (3 marks)

Ans.
a) Geometrical isomerism : - This type of isomerism is only due to different geometrical arrangement of atom or group in space. Compound having general formula.
.................................ABC=CAB


Cis form Tr
Ans form (one in which gr. of same type are on same side (one in which gr. of different types is called cis-isomers) are on different sides is called tr
Ans-isomers)

b) Optical isomerism: -This type of isomerism is only due to presence of at least one asymmetric carbon atom & the same compound behaves differently towards polarised light. The different forms are known as Optical isomerism. These are dextro or levo rotatory
(Hints: -A carbon atom having four different atoms or groups is called Asymmetric carbon atom, e.g. cabxy)

Q 28)Arrange the following in the decreasing order of property indicated:
(i) F₂, Cl₂, Br₂, I₂ Bond energy
(ii) HF, HCl, HBr, HI acid strength ( in water)
(iii) M-F, M-Cl, M-Br, M-I ionic character of the bond (mark-3)

Ans: -
(i) F₂> Cl₂> Br₂> I₂
As the size of the halide ion increases the energy of dissociation decrease.
(ii) HF> HCl> HBr> HI
Fluoric acid is stronger than hydrochlic acid.

(iii) M-F>M-Cl> M-Br> M-I

Q 29)What is Buna-S? How it is synthesised? (2 marks)

Ans. It is a synthetic rubber, obtained by polymerisation of butadiene & styrene. Bunna-S rubber:-
CH₂=CH-CH=CH + C₆H₅-CH-CH₂------------> (-CH₂=CH-CH=CH₂-CH-CH₂-)n
l................................................................................................|
................................................................................................C₆H₅
Butadiene Styrene ...........................................................Bunna-S

Q 30)Write nuclear equation for the following tr
Ansformations:
a) ²³³Th₉₀ undergoes ß-decay
b) ²¹⁸At₈₅ undergoes a-decay (3 marks)


Q 31) If the radioactive element 235X92 emits one alpha particle & two beta particles, then:
i) What will the atomic number & atomic mass of daughter elements "y".
ii) What will be the relation between parent element X & daughter elements Y.(mark-3)

Ans.

Q 32)Write down all the quantum number of the 8th electron of Cl -atom? (3 marks)

Ans.
Cl (17) 1s₂,2s₂, 2p₆,3s₂,3p₅
The arrangement of electron in Cl-atom in 2p orbital is shown below according to Hund's rule

Therefore, 8th electrons of Cl-atom are 2px orbital & its spin in the anticlockwise direction. It's four quantum no. are:
n=2, l=1, m= -1 & s= -1 /2

Q 33) Explain: -
i) Bronsted-Lowery acid-base concept
ii) Arrehenius theory (3 marks)

Ans.

· i) Bronsted-Lowery Theory: -
According to him,
" an acid is a proton donor while base is a proton acceptor"
HCl + H₂O  H₃O⁺ (aq) + Cl^- (aq)

ii)

· Bronsted-Lowery Theory: -
According to him,
" an acid is a proton donor while base is a proton acceptor"
HCl + H₂O  H₃O⁺ (aq) + Cl^- (aq)

· ii) Bronsted-Lowery Theory: -
According to him,
" an acid is a proton donor while base is a proton acceptor"
HCl + H₂O  H₃O⁺ (aq) + Cl^- (aq)

ii)

According to Arrehenius,
Acid: -
" An acid is a compound which contains replaceable hydrogen atom or atoms, a part or whole of which can be replaced by me
Ans of a metal or a positive radical".
· Base: -
According to Arrehenius,
"A base is a compound which contain replaceable oxide or hydroxide".

# Complete replacement by metals.
HCl + NaOH NaCl + H₂O
HNO₃ + NaOH NaNO₃ + H₂O
H₂SO₄ + 2NaOH Na₂SO₄ + 2H₂O
# Complete replacement by a group of elements called radical.
HCl + NH₄OH NH₄Cl + H₂O
HNO₃ + NH₄OH NH₄NO₃ + H₂O
# Partial replacement by metal or ammonium group: -
H₂SO₄ +NaOH NaHSO₄ + H₂O
H₂SO₄ + NH₄OH NH₄HSO₄ + H₂O

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