The most dangerous method of precipitating hydrogen would be by the action of HCl on:

1. Zn

2. Fe

3. K

4. Al

Which is industrially prepared by the electrolysis of aqueous NaCl?

1. Na₂CO₃

2. NaHCO₃

3. NaOH 

4. NaOCl

The products of the electrolysis of aqueous solution of common salt are:

1. Na + Cl₂

2. H₂ + O₂

3. NaOH + H₂ + Cl₂

4. NaOH + Cl₂ + O₂

Sodium cannot be extracted by the electrolysis of brine solution because:

1. sodium leberated reacts with water to produce NaOH+H₂

2. sodium being more electropositive than hydrogen, H₂ is liberated at cathod and not sodium

3. electrolysis cannot take place with brine solution

4. none of the above

KO₂ is used in oxygen cylinder in space air craft and submarines because it:

1. absorbs CO₂ and increase O₂ content

2. eliminate moisture

3. absorbs CO₂

4. produces O₂

Tin dissolves in boiling caustic soda solution because of the formation of soluble:

1. Sn(OH)₂

2. Sn(OH)₄

3. Na₂SnO₃

4. none of these

Potash alum is used in purification of water because:

1. it kills the micro-organisms

2. it precipitates the colloidal matter

3. it removes the hardness of water

4. it catalyses the removal of impurities

The pair of compounds which cannot exist together in solution is:

1. NaHCO₃ and NaOH

2. Na₂CO₃ and NaHCO₃

3. Na₂CO₃ and NaOH

4. NaHCO₃ and NaCl

Which one is the highest melting point halide?

1. NaCl

2. NaBr

3. NaF

4. NaI

The byproduct of the Solvay process is:

1. CO₂

2. NH₃

3. CaCl₂

4. CaCO₃