Which of the following liquid has the highest vapour pressure or is most volatile?

1. HF(l)

2. NH₃(l)

3. C₂H₅OH(l)

4. H₂O

The vapour pressure of the liquid depends upon

1. the amount of liquid taken

2. the temperature of the liquid

3. the volume of the vessel

4. both amount and temperature

Correct statement regarding the heating of a liquid is - 

1. Surface tension increases

2. Surface tension is lowered

3. Viscosity increases

4. Surface tension is not affected