The oxidation number and covalency of sulphur in the sulphur molecule (S₈) are respectively:

1. 0 and 2

2. +6 and 8

3. 0 and 8

4. +6 and 2

H₂S is passed through an acidified solution of copper sulphate and a black precipitate is formed. This is due to:

1. oxidation of Cu²⁺

2. reduction of Cu²⁺

3. double decomposition

4. reduction and oxidation

The most common oxidation state of an element is -2. The number of electrons present in its outermost shell is:

1. 2

2. 4

3. 6

4. 8

4P + 3KOH + 3H₂O $\to$ 3KH₂PO₂ + PH₃:

Correct statement regarding the above reaction is -

1. P oxidised only

2. P is reduced only

3. P is oxidised as well as reduced

4. None of the above

In which SO₂ acts as oxidant, while reacting with:

1. acidified KMnO₄

2. acidified K₂Cr₂O₇

3. H₂S

4. H₂0₂

In the reaction;

3Br₂ + 6C${\mathrm{O}}_3^{2-}$ + 3H₂O $\to$5Br^- + Br${\mathrm{O}}_3^{-}$ + 6HC${\mathrm{O}}_3^{-}$

which statement is correct?

1. Br₂ is oxidised

2. Br₂ is reduced

3. Br₂ is neither oxidised nor reduced

4. Br₂ is oxidised and reduced as well 

When NaCl is dissolved in water, the sodium ion becomes:

1. oxidised

2. reduced

3. hydrolysed

4. hydrated

If H₂S is passed through an acidified K₂Cr₂O₇ solution, the colour of the solution:

a. will remain unchanged

b. will change to deep red

c. will change to dark green

d. will change to dark brown 

Which of the following reactions does not represent a redox change?

1. CaCO₃ $\to$CaO + CO₂

2. 2H₂ + O₂ $\to$2H₂O

3. Na + H₂O $\to$ NaOH + \(\frac{1}{2}\)H₂

4. MnCl₃ $\to$ MnCl₂ + \(\frac{1}{2}\)Cl₂

Oxidation state of +1 for phosphorus is found in:

1. H₃PO₃ 

2. H₃PO₄

3. H₃PO₂

4. H₄P₂O₇