Chemistry:2006:CBSE:Board Paper
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Q1
A cubic solid is made of two elements X and Y. Atoms Y are at the corners of the cube and X at the body centre. What is the formula of the compound? Marks:1View AnswerAnswer:
The contribution due to Y atoms at corner = 1/8
Number of Y atoms at the corner = 8 x 1/8 = 1The contribution due to X atoms at the body centre = 1
Hence, theformula of the compound = XY -
Q2
Two liquids A and B boil at 145°C and 190°C respectively. Which of them has a higher vapour pressure at 80°C? Marks:1View AnswerAnswer:
A has higher vapour pressure than B at 800C because boiling point of A is lower than B. -
Q3
For the reaction A → B, the rate of reaction becomes twenty seven times when the concentration of A is increased three times. What is the order of the reaction? Marks:1View AnswerAnswer:
Rate law expression suggest that,
rate = k [A]n
or, r = k [A]n
according to question27 r = k[3A]n -------------- (ii) 27 r = 3nk[A]n 27 r = 3nr
27 = 3n 33 = 3n n = 3
Hence, order of reaction is 3
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Q4
Write the IUPAC name of: CH3.CH(Br)CH2CONHCH3. Marks:1View AnswerAnswer:
3-bromo-N-methylbutanamide -
Q5
Give a chemical test to distinguish between aniline and N-methyl aniline. Marks:1View AnswerAnswer:
Aniline gives carbylamine test but N-methyl aniline does not give this test. In this test when aniline is heated with chloroform and alcoholic KOH it forms foul smelling carbylamine. -
Q6
What is meant by entropy driven reaction? How can a reaction with positive changes of enthalpy and entropy be made entropy driven? out of syllabus
Marks:2View AnswerAnswer:
The reaction where
H is positive but -T S is numerically larger then it is known as entropy driven reaction.
G = H -T S
G should be negative for spontaneous reaction.
The reaction will become entropy driven if
(i) S is positive and is small but T must be large.
(ii)S is positive and is large but T must be small. -
Q7
Write balanced chemical equations for the following reactions:
(i)Ca3P2 + H2O → (ii) XeF6 + 3 H2O → Marks:2View AnswerAnswer:
(i) Ca3P2 + 6H2O → 3Ca(OH)2 + 2PH3 (ii) XeF6 + 3H2O → XeO3 + 6HF. -
Q8
Write chemical equations for the reactions involved in the manufacture of potassium permanganate from pyrolusite ore. Marks:2View AnswerAnswer:
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Q9
What are enantiomers? Draw the structures of the possible enantiomers of 3-methyl pent-1-ene. Marks:2View AnswerAnswer:
Those optical isomers which are non-superimposable mirror image of each other are called enantiomers or enantiomorphs.
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Q10
Write the reactions and the conditions involved in the conversion of:
a.Propene to 1-Propanol (1)
b.Phenol to Salicyclic acid (1) Marks:2View AnswerAnswer:
(a) Propene to 1-Propanol:-
(b) Phenol to Salicylic acid:- 
