Science (English Medium) Class 12 - CBSE Question Bank Solutions for Chemistry

Complete the following reaction and justify that it is a disproportionation reaction:

\[\ce{3MnO^{2-}4 + 4H^+ -> \underline{}\underline{}\underline{}\underline{} + \underline{}\underline{}\underline{}\underline{} + 2H2O}\]

The given graph shows the trends in melting points of transition metals:

Explain the reason why Cr has the highest melting point and manganese (Mn) has a lower melting point.

Consider the following standard electrode potential values:

\[\ce{Fe^{3+}_{ (aq)} + e^- -> Fe^{2+}_{ (aq)}}\], E⁰ = +0.77 V

\[\ce{MnO^{-4}_{ (aq)} + 8H^+ + 5e^- -> Mn^{2+}_{ (aq)} + 4H2O_{(l)}}\], E⁰ = +1.51 V

What is the cell potential for the redox reaction?

Which of the following ions has the electronic configuration 3d⁶?
(Atomic number: Mn = 25, Co = 27, Ni = 28)

A transition element X has an electronic configuration [Ar]4s²3d³. Predict its likely oxidation states.

Consider the following standard electrode potential values:

\[\ce{Sn^{2+}_{ (aq)} + 2e^- -> Sn_{(s)}}\]; E⁰ = −0.14 V

\[\ce{Fe^{3+}_{ (aq)} + e^- -> Fe^{2+}_{ (aq)}}\]; E⁰ = +0.77 V

What is the cell reaction and potential for the spontaneous reaction that occurs?

Write the number of unpaired electrons in Cr³⁺.
(Atomic number of Cr = 24)

Account for the following:

Copper has an exceptionally positive `"E"_("M"^(2+)//"M")^0` value.

Account for the following:

Eu²⁺ with electronic configuration [Xe]4f⁷6s² is a strong reducing agent.

The trend of which property is represented by the following graph?

In order to protect iron from corrosion, which one will you prefer as a sacrificial electrode, Ni or Zn? Why? (Given standard electrode potentials of Ni, Fe and Zn are -0.25 V, -0.44 V and -0.76 V respectively.)

The second ionization enthalpies of chromium and manganese are 1592 and 1509 kJ/mol respectively. Explain the lower value of Mn.

Give two similarities in the properties of Sc and Zn.

What is the oxidation state of chromium in chromate ion and dichromate ion?

Write the ionic equation for reaction of KI with acidified KMnO₄.

Calculate the standard cell potential of a galvanic cell in which the following reaction takes place:

\[\ce{Fe{^{2+}_{(aq)}} + Ag{^{+}_{(aq)}} -> Fe{^{3+}_{(aq)}} + Ag_{(s)}}\]

Calculate the Δ_rG° and equilibrium constant of the reaction.

Why are interstitial compounds well known for transition metals?

Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iron (II) solution.

Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H₂S.

For M²⁺/M and M³⁺/M²⁺systems, the E^Θ values for some metals are as follows:

Use this data to comment upon:

The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.