Chemistry:2011:CBSE:[Delhi ]:Set-III
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Q1
‘Crystalline solids are anisotropic in nature’. What does this statement mean?
Marks:1View AnswerAnswer:
This statement means that some of the physical properties of crystalline solids such as electrical resistance or refractive index show different values when measured along different directions in the same crystals.
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Q2
Write the IUPAC name of the following compound:
(CH3)3CCH2BrMarks:1View AnswerAnswer:
The IUPAC name of the given compound is 2, 2-dimethylbromopropane.
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Q3
Draw the structure of 3-methylbutanal.
Marks:1View AnswerAnswer:
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Q4
Arrange the following compounds in an increasing order of their solubility in water:
C6H5NH2, (C2H5)2NH, C2H5NH2Marks:1View AnswerAnswer:
The solubility order of the given amines is as follows:
C6H5NH2 < (C2H5)2NH < C2H5NH2 -
Q5
What is meant by ‘shape-selective catalysis’ of reactions?
Marks:1View AnswerAnswer:
A catalytic reaction which depends upon the pore structure of the catalyst and on the size of the reactant and the product molecules is called shape-selective catalysis.
For example, catalysis by zeolite is a shape-selective catalysis. The pore size present in the zeolite ranges from 260-740 pm. Thus, molecules having a pore size more than this cannot enter the zeolite and undergo the reaction. -
Q6
Express the relation among the conductivity of solution in the cell, the cell constant and the resistance of solution in the cell.
Marks:1View AnswerAnswer:
The conductivity of a solution, the cell constant and the resistance of a cell are related by the following expression.
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Q7
Draw the structure of BrF3 molecule.
Marks:1View AnswerAnswer:
BrF3 has a bent T-shape and can be drawn as follows.
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Q8
What do you mean by LDP and HDP?
Marks:1View AnswerAnswer:
LDP stands for low density polythene.
HDP stands for high density polythene.
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Q9
Distinguish between ‘rate expression’ and ‘rate constant’ of a reaction.
Marks:2View AnswerAnswer:
Rate expression: Rate expression can be defined as the expression in which the rate of reaction is given in terms of the molar concentration of the reactants with each term raised to some power, which may or may not be the stoichiometric coefficient of the reacting species in a balanced chemical equation.
Rate constant: The rate constant can be defined as the rate of the reaction when the concentration of each of the reactants is taken as unity.
Example: 2NO(g) + O2(g)
2NO2(g)The rate expression for the above reaction can be written as follows:
Rate=k[NO]2[O2] (Experimentally determined)
Now, if the concentration of NO and O2 is taken as unity, then the rate constant is found to be equal to the rate of the reaction.
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Q10
State reasons for each of the following:
(i) The N–O bond in NO2- is shorter than the N–O bond in NO3- .
(ii) SF6 is kinetically an inert substance.Marks:2View AnswerAnswer:
(i)The shorter N–O bond in NO2- is due to the existence of resonance in NO2–. The resonating structures can be drawn as follows:
Due to resonance in NO2–, the two bonds are equivalent (50% single and 50% double). This leads to a decrease in bond length.Now, the resonating structures for NO3– can be drawn as:
As seen from the above resonating structures of NO3–, the three bonds are equivalent, but three oxygen atoms are sharing two single bonds and one double bond. So, the mean N–O bond length lies closer to that of single bond. Therefore, the N–O bond in NO2- is shorter than the N–O bond in NO3-.(ii) The kinetic inertness of SF6 can be explained on the basis of its structure.
As seen from the above structure, the six fluoride (F-) atoms protect the sulphur atom from attack by the reagents to such an extent that even thermodynamically most favourable reactions like hydrolysis do not occur.
