List of top Chemistry Questions asked in CBSE CLASS XII

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 conductivity of sodium chloride at 298 K has been determined at different concentrations and the results are given below:
Concentration/M 0.001 0.010 0.020 0.050 0.100
10² × κ/S m^-1 1.237 11.85 23.15 55.53 106.74
Calculate \(\land_m\) for all concentrations and draw a plot between \(\land_m\) and c ½. Find the value of \(\land^0_m\).

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:

Acetylation
Cannizzaro reaction
Cross aldol condensation
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 xacetone	0	11.8	23.4	36.0	50.8	58.2	64.5	72.1
P_acetone /mm Hg	0	54.9	110.1	202.4	322.7	405.9	454.1	521.1
P_chloroform/mm Hg	632.8	548.1	469.4	359.7	257.7	193.6	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.

Compare the chemistry of actinoids with that of the lanthanoids with special reference to:
(i) electronic configuration (iii) oxidation state
(ii) atomic and ionic sizes and (iv) chemical reactivity.

Predict which of the following will be coloured in aqueous solution? Ti³⁺ ,V³⁺ , Cu⁺ , Sc³⁺ , Mn²⁺ , Fe³⁺ and Co²⁺ . Give reasons for each.

For M²⁺/M and M³⁺/M²⁺ systems, the \(E^\ominus\) values for some metals are as follows:
Cr²⁺/Cr -0.9V
Cr³ /Cr²⁺ -0.4 V
Mn²⁺/Mn -1.2V
Mn³⁺/Mn²⁺ +1.5 V
Fe²⁺/Fe -0.4V
Fe³⁺ /Fe²⁺ +0.8 V
Use this data to comment upon:
(i) The stability of Fe³⁺ in acid solution as compared to that of Cr³⁺ or Mn³⁺ and
(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

Describe the preparation of potassium permanganate. How does the acidifiedpermanganate solution react with (i) iron(II) ions (ii) SO₂and (iii) oxalic acid? Write the ionic equations for the reactions.