do redox reactions release or consume energy?

if the chemicals flouorine and hydrogen are put together, will they always redox like this:
H2 + F2 → 2 HF

Is it possible to break 2HF into fluorine and hydrogen - do you need heat to do it?

Question

do redox reactions release or consume energy?

if the chemicals flouorine and hydrogen are put together, will they always redox like this:
H2 + F2 → 2 HF

Is it possible to break 2HF into fluorine and hydrogen - do you need heat to do it?

aaronq · Answer

it can be both, depending on which way the electrochemical cell is set up.

When written $H_2 + F_2 → 2 HF$ ;$E^o_{cell}=-ve$, which is spontaneous, they're 
called voltaic/galvanic cells and can be used  to do work, e.g. working a cell phone.  If reversed $H_2 +  F_2 → 2 HF$ $E^o_{cell}=+ve$, is not spontaneous, and require an energy input. These are called electrolytic cells - plugging a cell phone in an outlet in your house to charge it.

anonymous · Answer

thanks a lot for your reply

oxidization is defined to be a reaction that releases electrons, right? is it a general rule that released electrons is also released energy like heat?