The correct structure of pyrophosphoric acid is:

1.		2.
3.		4.

PH₃ forms bubbles when passed slowly through water but NH₃ gets dissolved in water, because: 

The disproportionation reaction of ${\mathrm{H}}_3{\mathrm{PO}}_3$ is as follows:

${\mathrm{H}}_3{\mathrm{PO}}_3$ $\stackrel{∆}{\to }$ $\mathrm{X}$ $+$ $\mathrm{Y}$

 X and Y in the above reaction are:

1. H₃PO₂, HPO₂  

2. H₃PO₄, PH₃

3. H₂PO₆, PO₃

4. None of the above.

The correct increasing order of basic strength of hydrides:

1. BiH₃ \(\simeq \) SbH₃ < AsH₃ < PH₃ < NH₃ 
2.  BiH₃  > NH₃  > PH₃ > SbH₃ > AsH₃ 
3. SbH₃ < AsH₃ < PH₃ < NH₃ < BiH₃ 
4. AsH₃ > NH₃ > PH₃ > SbH₃ > BiH₃

A balanced chemical equation for the reaction showing catalytic oxidation of NH₃ by atmospheric oxygen is:

An element that does not show allotropy is:
1. Nitrogen
2. Phosphorus
3. Antimony
4. Arsenic

A brown ring formed in the ring test for ${\mathrm{NO}}_3^{-}$ ion is due to the formation of:
1. [Fe(H₂O)₅(NO)]²⁺
2. FeSO₄.NO₂
3. [Fe(H₂O)₄(NO)₂]²⁺
4. FeSO₄.HNO₃

Which of the following statements is correct? 

 Match the formulas of oxides given in Column I with the type of oxide given in Column II and mark the correct option.

Codes

The bonding present in nitrogen molecules is:
1. \(p\pi-p\pi\)
2. \(p\pi-d\pi\)
3. \(d\pi-d\pi\)
4. Only sigma bond