what would happen if you burnt liquid nitrogen would it create energy?

Answer 1

Chemically yes. Overall, no. Plain and simple, the chemical reaction alone will release energy (NOT "create" it), but the man-made processes as known so far have enormous activation energy requirements (to speed the reaction up to reasonable rates) that overwhelm the chemical energy output.

Lets discuss. Use the gibbs free energy equation: deltaG=deltaH-TdeltaS. We'll attack the enthalpy first, because I have the numbers in my head. "Burning" in this case means inputting energy to break the N-N triple bond and the O-O double bond, and releasing energy by recombining the two N atoms with various oxygen atoms. For a specific example, let's say you're breaking one N2 bond and two O2 bonds, and forming two molecules of NO2. Balancing the equation and using the bond energies of one N2, two O2 and four N=O bonds, this is roughly 950 + 2(500) - 4(600), or a total of - 550 kJ/mol. So deltaH is quite negative.

As for the entropy, I am guessing that it will be mildly negative (unfavorable) , because you're reacting three gas molecules and producing two.

All in all, plugging these values into the gibbs equation above means the process will be quite thermodynamically favorable until the temperature gets really huge, but... any reaction involving N2 bond breaking has a very, very large activation energy, which the gibbs free energy equation does not tell you about! This is in large part because dinitrogen is totally nonpolar and nonpolarizable, which makes it a very uninviting target for nucleophilic attack, and also makes it very unlikely to attack. That is why nitrogen fixation works (it is thermodynamically favorable) but is very difficult to do (it is kinetically very hard to activate).

Using liquid dinitrogen rather than gaseous dinitrogen would require a small amount more energy input to warm it enough to overcome that reaction barrier. So for liquid nitrogen the answer is still chemically yes, but it will require slightly more energy to react, resulting a slightly larger overall no.

The haber-bosch process (analogous to the above, but with different bonds being formed and broken) uses high temperature (which would combine with the small negative entropy to make the whole process unfavorable), but makes the entropy more favorable by using high pressure, resulting in, again, a thermodynamically favorable process that nonetheless requires an enormous amount of energy input, more than is released.

In short, as yet nitrogen fixation ("burning") is an energy sink, not an energy source. So far, only plants and a few small metal complexes can break the N-N triple bond at anything like a reasonable temperature, and they do it by reducing the activation energy. I truly invite you to try, though. You'll get a nobel prize very quickly if you can combine dinitrogen and dioxygen, and release more energy than you put in. Honestly, the more people that are trying, the better.

Answer 2

Actually, there's no proof yet that life didn't start on Mars too. As a matter of fact, most scientists believe that Mars did once have life. The reason Mars is a dead planet now is because of it's size. It cooled too quickly and lost it's magnetic poles, which allowed the solar winds to strip away the majority of it's atmosphere. And fyi, 12 billion years ago, neither Earth nor Mars existed yet. Plus, it takes a lot more than water & oxygen for life to survive & flourish. You really need to go back to school.

Answer 3

Nitrogen gas and nitrogen liquid are not flammable. So, you could hold a match to them all day long and nothing would happen, except that you'd freeze your fingers off.

Answer 4

The reaction between N2 and O2 actually absorbs energy. Otherwise you would not have them both free in the atmosphere for billions of years.