Question

if you push your chair across the floor at a constant velocity how does the force of friction compare with the force you exert?

Answer 1

The force of friction is equal but opposite to the force that you exert. This is due to newtons 3rd law 'For every action there is an equal but opposite reaction'

Answer 2

-- If velocity is constant, then there is no net force
on the chair.

-- If there is no net force on the chair, then friction
must exactly balance out your push.

-- The force of friction is exactly equal in magnitude
to your push, and in exactly the opposite direction.