How can one obtain sulphur trioxide?

1. CaSO₄ + C$\stackrel{∆}{\to }$                         

2. Fe₂(SO₄)₃$\stackrel{∆}{\to }$

3. S + H₂SO₄$\stackrel{∆}{\to }$                         

4. H₂SO₄ + PCl₅ $\stackrel{∆}{\to }$

The correct statement about given acids is:

Copper on heating with concentrated HNO₃ produces:

1. Cu(NO₃)₂ and NO       

2. Cu(NO₃)₂, NO and NO₂

3. Cu(NO₃)₂ and N₂O       

4. Cu(NO₃)₂ and NO₂

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

Which of the following statements is true? 

Which of the following is in the correct sequence?

[For the correct order mark (T) and for the incorrect order mark (F)]:

Incorrect statement regarding PH₃ is:

1. It is produced by the hydrolysis of Ca₃P₂${\mathrm{}}_{}$

2. It gives a black ppt, Cu₃P₂ with a CuSO₄ solution.

3. It spontaneously burns in the presence of ${\mathrm{P}}_2{\mathrm{H}}_4$

4. It does not react with ${\mathrm{B}}_2{\mathrm{H}}_6$

The false statement regarding hydrides from the 15th group is:

The gas that cannot be collected over water is:

1. ${\mathrm{N}}_2$                                   

2. ${\mathrm{O}}_2$

3. ${\mathrm{SO}}_2$                                 

4. ${\mathrm{PH}}_3$