Question

what is the pressure at the free surface of the liquid

Answer 1

At the surface, pressure can be anything depending on what is there above the liquid. 
For example, if there is nothing i.e. vacuum, then pressure is 0.
If there is air, then it will be same as the air pressure at that point.

Answer 2

At the surface pressure can be anything depending on what is there above the liquid

for example if there is nothing that is vacuum then pressure is zero

if there is air then it will be same as air pressure at the point