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106 questions

Class 12 · Chemistry
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the [4×1] brackets: [four, three, remains same, propane, ns1-2, increases, six, propan-2-ol, (n-1)d1-10, two, decreases, Clemmensen’s, Wolff-Kishner]
In the complex ion [CoCl(en)2ONO]+, the coordination number and
the oxidation number of the central metal ion are ______ and
________.
Short answer
Class 12 · Chemistry
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the [4×1] brackets: [four, three, remains same, propane, ns1-2, increases, six, propan-2-ol, (n-1)d1-10, two, decreases, Clemmensen’s, Wolff-Kishner]
Given below are two statements marked Assertion and Reason. Read the two
statements carefully and select the correct option.
Assertion: Tertiary butyl bromide undergoes Wurtz reaction to give 2,2,3,3
tetramethyl butane.
Reason: In Wurtz reaction, when same alkyl halides react with sodium in dry
ether to give hydrocarbon; the hydrocarbon formed contains double
the number of carbon atoms present in the alkyl halide.
MCQ
Class 12 · Chemistry
3] Consider the data given below for the reaction A + B Product S.No. conc. of [A] mol L-1 conc. of [B] mol L-1 Rate; mol L-1sec-1 1. 0·1 0·1 4·0 × 10- 4 2. 0·2 0·2 1·6 × 10- 3 3. 0·5 0·1 1·0 × 10- 2 4. 0·5 0·5 1·0 × 10- 2 Answer the following questions.
What is the order of reaction with respect to A and B?
Short answer
Class 12 · Chemistry
Calculate the abnormal molecular mass of solute in both the cases.
Numerical
Class 12 · Chemistry
(a) Calculate the boiling point of urea solution when 8·0g of urea is dissolved
in 250g of water. Boiling point of pure water is 373K.
(kb of water = 0·52 K kg mol-1, molecular mass of urea = 60 g mol-1)
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(b) Ethylene glycol is used as an antifreeze agent. Calculate the amount of
ethylene glycol to be added to four kilogram of water to prevent it from
freezing at -6oC.
(Kf of water = 1·86 K kg mol-1) Assume that ethylene glycol
(CH2OH.CH2OH) does not dissociate or associate in aqueous solution.
(c) What will be the effect on the value of molality and molarity of a solution
with change in temperature?
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CHEMISTRY
Numerical
Class 12 · Chemistry
On the basis of Crystal Field Theory, write the electronic configuration of d4 ion
if:
(a) ∆o > P
(b) ∆o< P
Short answer
Class 12 · Chemistry
Assuming that cyanide is a strong ligand, write the formula of two coordination
complex ions with cyanide and iron having coordination number six. Name the
complex ions.
Short answer
Class 12 · Chemistry
Dry cells are commonly used in clocks, torches, calculators etc. They are the
most familiar type of commercial cells.
(a) What acts as anode and cathode in dry cell?
(b) Which chemical compounds are filled between anode and cathode of this
cell?
(c) Why do dry cells not have a long life?
OR
Short answer
Class 12 · Chemistry
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the [4×1] brackets: [four, three, remains same, propane, ns1-2, increases, six, propan-2-ol, (n-1)d1-10, two, decreases, Clemmensen’s, Wolff-Kishner]
The correct order of the increasing basic nature of Ammonia,
Methylamine and Aniline is:
MCQ
Class 12 · Chemistry
(A) Fill in the blanks by choosing the appropriate word(s) from those given in the [4×1] brackets: [four, three, remains same, propane, ns1-2, increases, six, propan-2-ol, (n-1)d1-10, two, decreases, Clemmensen’s, Wolff-Kishner]
The half-life period (t1/2) for a first order reaction is 30 minutes.
Calculate the time taken to complete 87·5% of the reaction.
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Numerical
Class 12 · Chemistry
Give a reason for each of the following.
(a) The purple colour of KMnO4 disappears in the presence of acidified
solution of oxalic acid.
(b) Some transition metals and their compounds get attracted towards the
magnetic field.
(c) 2+ 2+
Why are Mn compounds more stable than Fe towards oxidation to the
+3 state? (atomic no. of Mn = 25 and Fe = 26)
Short answer
Class 12 · Chemistry
3] Consider the data given below for the reaction A + B Product S.No. conc. of [A] mol L-1 conc. of [B] mol L-1 Rate; mol L-1sec-1 1. 0·1 0·1 4·0 × 10- 4 2. 0·2 0·2 1·6 × 10- 3 3. 0·5 0·1 1·0 × 10- 2 4. 0·5 0·5 1·0 × 10- 2 Answer the following questions.
Determine the reaction rate when the concentration of A and B are
0·2 mol L-1sec-1 and 0·35 mol L-1sec-1 respectively.
Short answer
Class 12 · Chemistry
Identify the compounds [A] and [B ] in the following reactions.
(1) K2Cr2O7/H2SO4 C6H6(anhy. AlCl3)
(a) C6H5CHO [A] [B]
(2) SOCl2
(1) H2SO4/HgSO4 C2H5OH
CH3-C≡CH [A] [B]
(b) (2) vigorous oxidation, [conc. H2SO4]
conc.HNO3
OR
Short answer
Class 12 · Chemistry
Given below is the increasing order of depression in freezing point of
water observed for equimolar concentrations of the compounds,
acetic acid < trichloro acetic acid < trifluoro acetic acid
Provide a reason to explain if the above ordered arrangement is correct or
not.
Short answer
Class 12 · Chemistry
Inferring the value of van’t Hoff factor in both the cases, find out which
solution undergoes association and which solution undergoes
dissociation.
Short answer
Class 12 · Chemistry
Write the reaction when phenol is treated with chloroform in the presence of
aqueous NaOH at 340K.
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Short answer
Class 12 · Chemistry
Write the chemical equation for the preparation of phenol from benzene using
H2SO4 and NaOH.
Short answer
Class 12 · Chemistry
What happens when phenol reacts with Br2/CS2 at low temperature?
Short answer
Class 12 · Chemistry
Write the reaction when phenol is treated with conc. HNO3 in the presence of
conc. H2SO4.
Short answer
Class 12 · Chemistry
Three organic compounds A, B and C are non cyclic functional isomers of
carbonyl compounds with molecular formula C4H8O. Isomers A and C give
positive Tollen’s test while compound B does not give positive Tollen’s test but
gives positive iodoform test. Compounds A and B on reduction with Zn amalgam
and conc. HCl give the same product.
(a) Write the structures of the compounds A, B and C.
(b) Out of the compounds A, B and C, which one will be the least reactive
towards addition of HCN.
Short answer