The physical property of hydrides of group 16 that decreases down the group is:

1.	Melting point	2.	Thermal stability
3.	Boiling point	4.	Critical temperature

Which of the following statements about acid strength is false?

1. $\mathrm{HI}>\mathrm{HBr}>\mathrm{HCl}$                               

2. ${\mathrm{HIO}}_4>{\mathrm{HBrO}}_4>{\mathrm{HCIO}}_4$

3. ${\mathrm{HClO}}_4>{\mathrm{HClO}}_3>{\mathrm{HClO}}_2$                 

4. $\mathrm{HF}>{\mathrm{H}}_2\mathrm{O}>{\mathrm{NH}}_3$ 

Concentrated nitric acid reacts with iodine to give :

(1) $\mathrm{HOI}$                             

(2) $\mathrm{HI}$

(3) ${\mathrm{HIO}}_3$                         

(4) ${\mathrm{HIO}}_4$

Thermally most stable compound is :

(1) ${\mathrm{HOCIO}}_3$                             

(2) ${\mathrm{HOCIO}}_2$

(3) $\mathrm{HOCl}$                                 

(4) $\mathrm{HOCIO}$ 

Which of the following halogen oxide  is used for estimation of carbon monoxide in automobile exhaust gases?

(1) ${\mathrm{Cl}}_2{\mathrm{O}}_7$                                 

(2) ${\mathrm{I}}_2{\mathrm{O}}_5$

(3) ${\mathrm{ClO}}_2$                                   

(4) ${\mathrm{BrO}}_3$

Only iodine forms hepta-fluoride ${\mathrm{IF}}_7$, but chlorine and bromine give Penta-fluorides. The reason for this is :

(1) low electron affinity of iodine

(2) unusual pentagonal bipyramidal structure of ${\mathrm{IF}}_7$

(3) that the larger iodine atom can accommodate more number of smaller fluorine atom around it 

(4) the low chemical reactivity of ${\mathrm{IF}}_7$

Nitrogen gas is liberated by thermal decomposition of :

(1) ${\mathrm{NH}}_4{\mathrm{NO}}_2$                                 

(2) ${\mathrm{NaN}}_3$

(3) ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$                           

(4) All    

Two oxides of nitrogen, $\mathrm{NO}$ and ${\mathrm{NO}}_2$ are allowed to react together at $243° \mathrm{K}$ and form a coloured compound of nitrogen (X). When compound (X) reacts with water to yield another compound of nitrogen (Y). The shape of the anion of (Y) molecule is :

(a) triangular planar                              (b) triangle pyramidal

(c) tetrahedron                                      (d) square planar 

Consider the following sequence of reaction.

$\mathrm{Na}+{\mathrm{NH}}_3\left(\mathrm{g}\right)\underset{}{\to }\left[\mathrm{X}\right]\stackrel{{\mathrm{N}}_2\mathrm{O}}{\to }\left[\mathrm{Y}\right]\stackrel{\mathrm{Heat}}{\to }\underset{\mathrm{Gas} \mathrm{Pure}}{\left[\mathrm{Z}\right]}$

Identify [Z] gas :

$\left(\mathrm{a}\right) {\mathrm{N}}_2$

$\left(\mathrm{b}\right) {\mathrm{NH}}_3$

$\left(\mathrm{c}\right) {\mathrm{O}}_2$

$\left(\mathrm{d}\right) {\mathrm{H}}_2$

Which of the following statements is true?