In which of the following compounds, an element exhibits two different oxidation state?

1.	${\mathrm{NH}}_2\mathrm{OH}$	2.	${\mathrm{NH}}_4{\mathrm{NO}}_3$
3.	${\mathrm{N}}_2{\mathrm{H}}_4$	4.	${\mathrm{N}}_3\mathrm{H}$

Which of the following arrangements represents the increasing oxidation number of the central atom?

1. ${\mathrm{CrO}}_2^{-},$ ${\mathrm{ClO}}_3^{-},$ ${\mathrm{CrO}}_4^{2-},$ ${\mathrm{MnO}}_4^{-}$

2. ${\mathrm{ClO}}_3^{-},$ ${\mathrm{CrO}}_4^{2-},$ ${\mathrm{MnO}}_4^{-},$ ${\mathrm{CrO}}_2^{-}$

3. ${\mathrm{CrO}}_2^{-},$ ${\mathrm{ClO}}_3^{-},$ ${\mathrm{MnO}}_4^{-},$ ${\mathrm{CrO}}_4^{2-}$

4. ${\mathrm{CrO}}_4^{2-},$ ${\mathrm{MnO}}_4^{-},$ ${\mathrm{CrO}}_2^{-},$ ${\mathrm{ClO}}_3^{-}$

Match Column I with Column II for the oxidation states of the central atoms.

Codes:

Match the items in Column I with relevant items in Column II.

Codes:

Given below are two statements: 

Arrange the given reduction potentials of some ions in decreasing order of oxidising power:

Which two changes occur in the oxidation number of chlorine when chlorine gas is passed through hot NaOH solution?

a. 0 to +5

b. 0 to +3

c. 0 to -1

d. 0 to +1

Choose the correct option:

1. (a, b)
2. (b, c)
3. (c, d)
4. (a, c)

In which of the following reactions conc. H₂SO₄ is used as an oxidising reagent?

Choose the correct option:

Which of the following statement regarding the rules to calculate the oxidation number is incorrect?