<p>Yeesh.. this one is tough it's on a take home test in my chem class. All help is appreciated:</p>
<p>Given the following data:</p>
<p>2NH3 + 3N2O -> 4N2 + 3H2O............DELTA H= -1010 kJ
N2O + 3H2 -> N2H4 + H2O...............DELTA H= -317 kJ
2NH3 + 1/2 O2 -> N2H4 + H2O..........DELTA H= -143 kJ
H2 + 1/2 O2 -> H2O........................DELTA H= -286 kJ</p>
<p>Calculate DELTA H for the reaction</p>
<p>N2H4 + O2 -> N2 + 2H2O</p>
<p>Thx in advance..</p>
<p>Flip around the equations so that, most likely by using all 4 given eqs, you cancel out the same compounds on each side so that your left with the equation your looking for. </p>
<p>Sry, I don't have the time to do it right now, but I hope you get the idea. </p>
<p>Btw: When flipping, make sure to reverse the Enthalpy. </p>
<p>-WiNgZ</p>
<p>Hess' Law...!!
It's like systems of equations.</p>
<p>Ok, I think I got it.. it's been years since I've had to do a problem like this..
Ok, first I took:
3N2H4+3H20 --> 3N2O + 9H2........... (3(317 kJ))
N2H4+ H2O --> 1/2 O2 +2NH3 ......... (-143 kJ)
now, on the product side you have:
3N2O+2NH3 which turns into 4N2+3H2O .... (-1010 kJ)
Overall now you have:
4N2H4 + H2O---> 4N2 + 1/2 O2 + 9H2
(You cancel out the waters on each side)
the oxygen & H form another water on the products side (-286)
Now you have:
4N2H4 --> 4N2 + 8H2
which you can simplify to: N2H4 --> N2 + H2
Now to turn that H2 into some water add on : 2H2+ O2 --> 4H2 + 2H20 -- 2(-296)</p>
<p>So overall now you have: N2H4 + O2 --> N2 + 2H2O :)
I didn't add up the delta H's.. don't have my calc with me</p>
<p>*typo:
which you can simplify to: N2H4 --> N2 + 2H2... forgot the 2 infront of the H2</p>
<p>its just Hess's Law
its not too bad
i dont think we're supposed to help u on ur take home test</p>