Hydrazine, H_2NH_2, is used as a rocker fuel. Use the data below to determine if
ID: 1072797 • Letter: H
Question
Hydrazine, H_2NH_2, is used as a rocker fuel. Use the data below to determine if hydrazine be prepared from the following reaction under standard conditions: N_2(g) + 2 h_2(g) rightarrow H_2NNH_2(I) delta H degree_f (kf/mol) 0 0 50.63 s degree (J/K.mol0 192.0 130.7 121.2 Calculate delta S_total for the following reaction, then tell whether it is spontaneous under standard conditions or not. CaCO_3(s) rightarrow CaO(s) + CO_2(g) delta H degree_f (kj/mol) -2106.9 -635.1 -393.5 s degree (J/K.mol) 92.9 39.7 213.6Explanation / Answer
Q. 1
For the formation of hydrazine is carried our under standard conditions. hence the temperature of the reaction is absolute temperature, i.e. 298K.
total entropy change = H0 = H0product - H0reactant
= 50.63 - 0
= 50.63 kJ/mol
Total entropy change = S0 = S0product - S0reactant
= (121.2) - (192.0 + 130.7)
= -201.5 J/K.mol = -0.2015 kJ/K.mol
Now applying Gibb's free energy equation,
G = H - TS
G = 50.63 - (298* -0.2015)
= 50.63 - (-60.047)
= 110.667 kJ/mol
Since the G is positive, The reaction is non spontaneous
Q.2
The given reaction is carried our under standard conditions. hence the temperature of the reaction is absolute temperature, i.e. 298K.
for the reaction given, The total entropy change is
Stotal = Sproduct - Sreactant
= (39.7 + 213.6) - (92.9)
= 160.4 J/K.mol = 0.1604 kJ/K.mol
the change in enthalpy for the reaction is
H0 = H0product - H0reactant
= (-635.1-393.5) - (-1206.9)
= 178.3 kJ/mol
to calculate Gibb's free energy
G = H - TS
= 178.3 - (298*0.1604)
= 130.5008 kJ/mol
since the G is positive, the reaction is non spontaneous under standard conditions.
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