PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Chemistry

Which of the following cations are coloured in aqueous solutions and why ?

Sc³⁺, V³⁺, Ti⁴⁺, Mn²⁺ (At. Nos. Sc = 21, V = 23, Ti = 22, Mn = 25)

How would you account for the following? 

Transition metals exhibit variable oxidation states.

Complete the following chemical equations:

`(i) Cr_2O_7^(2-)+6Fe^(2+)+14H^+ ->`

`(ii) 2CrO_4^(2-)+2H^+ ->`

`(iii) 2MnO_4^-+5C_2O_4^(2-)+16H^+ ->`

Pb(NO₃)₂ on heating gives a brown gas which undergoes dimerisation on cooling? Identify the gas

Account for the following:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.

Account for the following: 

Cr²⁺ is a strong reducing agent.

Account for the following:

Cu⁺² salts are coloured, while Zn²⁺ salts are white.

The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co

Answer the following: Write the element which shows maximum number of oxidation states. Give reason.

The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co

Answer the following: Which element has the highest m.p?

The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co

Answer the following: Which element shows only +3 oxidation state?

The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co

Answer the following: Which element is a strong oxidising agent in +3 oxidation state and why?

Why do the transition elements have higher enthalpies of atomisation?

In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?

Give reasons for the following observations:

Physisorption decreases with increase in temperature.

How would you account for the following: Transition metals form complex compounds.

Write the names and structures of the monomers of the following polymers: Buna-N

Differentiate between adsorbtion and absorption.

Give reasons:

Transition metals show variable oxidation states.

What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3^rd of tetrahedral voids?

What are the transition elements? Write two characteristics of the transition elements.