111 Calculate Hno for the reaction N2H4 l O2 g N2 g 2 H2O

111. Calculate H.no for the reaction: N2H4 (l) + O2 (g) N2 (g) + 2 H2O (l) Given the following reactions and their respective enthalpy changes. AHP =-1010. kJ 2 NH3 (g) + 3 N2O (g) 4 N2 (g) + 3 H2O (1) N2O (g) + 3 H2 (g) N2H4 (l) + H2O (l) 2 NH3 (g) + 2 O2 (g) N2H4 (l) + H2O (l) H2 (g) + O2 (g) H2O (l) AHP =-317kJ

Solution

Given reaction is

N2H4_(l) + O2_(g) ---> N2_(g) + 2H2O_(l)

consider reaction for Eliminating NH3

2(NH3) + 3(N2O) ---> 4(N2) + 3(H2O)    H -1010.0 kJ
+
N2H4 + H2O ---> 2(NH3) + 1/2(O2) H +143 kJ (reaction reverse H become +ve)
--------------------------------------------------------------------
N2H4 + 3(N2O) ---> 4(N2) + 2(H2O) + 1/2(O2)     H -867 kJ   -----------(A)

After the addition, there is 2(NH3) on both sides, we cancel it.
For H2O, there is 1 on the left and 3 on the right. Canceling out will leave us 2(H2O) on the right only. Then we add the H\'s of the rxns.

Now consider reaction for Eliminating N2O

(N2O) + (3H2) ---> (N2H4) + (H2O) H -317 kJ   multiplying this by 3 and reversed so
3(N2H4) + 3(H2O) ---> 3(N2O) + 9(H2)     H +951 kJ

Then add with reaction A
N2H4 + 3(N2O) ---> 4(N2) + 2(H2O) + 1/2(O2) H -867 kJ
+
3(N2H4) + 3(H2O) ---> 3(N2O) + 9(H2) H +951 kJ
--------------------------------------...
4(N2H4) + H2O ---> 4(N2) + 1/2(O2) + 9(H2) H 84 kJ ---------------(B)

both side 3(N2O) get cancel and two H2O from both side and one is remaining at left side.

Now consider reaction to Eliminating H2

(H2) + 1/2(O2) ---> (H2O)   H -286 multiplying by 9 we get

9(H2) + 9/2(O2) ---> 9(H2O) H -2574 kJ then add it with reaction B

4(N2H4) + H2O ---> 4(N2) + 1/2(O2) + 9(H2) H 84 kJ
+
9(H2) + 9/2(O2) ---> 9(H2O) H -2574 kJ
--------------------------------------...
4(N2H4) + 4(O2) ---> 4(N2) + 8(H2O) H -2490 kJ ------------(C )

both side 9(H2) get cancel ½ O2 right side. From right side and H2o from left side get cancel. So we get new reaction (C)

now devide reaction C we have get our proposed reaction that is
(N2H4) + 4(O2) ---> 4(N2) + 8(H2O) H -2490 kJ ------------(C ) devide by 4
N2H4 + O2 ---> N2 + 2(H2O) H -622.5 kJ