List of top Chemistry Questions asked in CBSE CLASS XII

A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is
(i) doubled
(ii) reduced to half?

Compare the stability of +2 oxidation state for the elements of the first transition series

How is 1-propoxypropane synthesised from propan-1-ol?Write mechanism of this reaction.

A solution is obtained by mixing 300 g of \(25\%\) solution and 400 g of \(40\%\) solution by mass. Calculate the mass percentage of the resulting solution.
How many mL of 0.1 M HCL are required to react completely with 1g mixture of \(\text{Na}_2\text{CO}_3\) and \(\text{NaHCO}_3\) containing equimolar amounts of both?
A solution of glucose in water is labelled as \(10\%\) \(\text{w/w}\), what would be the molality and mole fraction of each component in the solution? If the density of solution is \(1.2\, \text{g mL}^{–1}\), then what shall be the molarity of the solution?
Concentrated nitric acid used in laboratory work is \(68\%\) nitric acid by mass in aqueous solution. What should be the molarity of such a sample of the acid if the density of the solution is \(1.504\, \text{g mL}^{–1}?\)
Give an example of a solid solution in which the solute is a gas.
How much electricity is required in coulomb for the oxidation of 
(i) 1 mol of H2O to O2. 
(ii) 1 mol of FeO to Fe2O3.

How much electricity in terms of Faraday is required to produce
 (i) 20.0 g of Ca from molten CaCl2.
 (ii) 40.0 g of Al from molten Al2O3.

Conductivity of 0.00241 M acetic acid is 7.896 × 10-5 S cm-1 . Calculate its molar conductivity and if \(\land^0_m\) for acetic acid is 390.5 S cm2 mol-1 , what is its dissociation constant?
The resistance of a conductivity cell containing 0.001M KCl solution at 298 K is 1500 Ω. What is the cell constant if conductivity of 0.001M KCl solution at 298 K is 0.146 x 10-3 S cm-1 .
The conductivity of 0.20 M solution of KCl at 298 K is 0.0248 Scm-1 . Calculate its molar conductivity.
Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.
Calculate the standard cell potentials of galvanic cells in which the following reactions take place: 
 (i)  \(2Cr_{(S)}+3Cd^{2+}_{(aq)} \rightarrow 2Cr^{3+}_{(aq)}+3Cd\)
 (ii) \(Fe^{2+}_{(aq)}+Ag^+_{(aq)} \rightarrow Fe^{3+}_{(Aq)}+Ag(s)\)
Calculate the \(\triangle_rG^\ominus\) and equilibrium constant of the reactions.
Given the standard electrode potentials, 
K+/K = -2.93V, Ag+/Ag = 0.80V, 
Hg2+/Hg = 0.79V 
Mg2+/Mg = -2.37 V, Cr3+/Cr = - 0.74V 
Arrange these metals in their increasing order of reducing power.
Arrange the following metals in the order in which they displace each other from the solution of their salts.
Al, Cu, Fe, Mg and Zn

Show how will you synthesize:(i) 1-phenyl ethanol from a suitable alkene.
(ii) cyclohexyl methanol using an alkyl halide by an SN2 reaction.
(iii) pentane-1-ol using a suitable alkyl halide?

Write the equation of the reaction of hydrogen iodide with:

(i)1-propoxypropane 

(ii)methoxybenzene 

(iii)benzyl ethyl ether.

Describe the following:
  1. Acetylation
  2. Cannizzaro reaction
  3. Cross aldol condensation
  4. Decarboxylation

Vapour pressure of pure acetone and chloroform at 328 K are 741.8 mm Hg and 632.8 mm Hg respectively. Assuming that they form ideal solution over the entire range of composition, plot p_total  p_chloroform and p_acetoneas a function of x_acetone. The experimental data observed for different compositions of mixture is

100 X xacetone011.823.4  36.050.8 58.264.572.1
P_acetone /mm Hg054.9110.1202.4322.7405.9  454.1521.1
P_chloroform/mm Hg632.8 548.1   469.4359.7257.7193.6 161.2 120.7
Draw the structures of the following compounds.
(i) 3-Methylbutanal
(ii) p-Nitropropiophenone
(iii) p-Methylbenzaldehyde
(iv) 4-Methylpent-3-en-2-one
(v) 4-Chloropentan-2-one
(vi) 3-Bromo-4-phenylpentanoic acid
(vii) p,p'-Dihydroxybenzophenone
(viii) Hex-2-en-4-ynoic acid

The rate constant for the first order decomposition of \(H_2O _2\) is given by the following equation:
\(log\  k = 14.34 - 1.25 \times  10^4\  K/T \)
Calculate \(E_a\) for this reaction and at what temperature will its half-period be 256 minutes?

The rate of a reaction quadruples when the temperature changes from \(293 \ K\) to \(313\  K\). Calculate the energy of activation of the reaction assuming that it does not change with temperature.

What is meant by 'disproportionation'? Give two examples of disproportionation reaction in aqueous solution.