Thankyou!!!
this makes more sense..In summary wheny you have enthalpy of formation delta 1=delta2 + delta 3. And enthalpy of cumbustion: delta 1= delta 2-delta 3. However How would I answer questions like this:
Alkane formula Hc/kJ mol-1
Methane CH4 –890
Ethane C2H6 –1560
Propane C3 H8 –2220
(i)
[2]
(iii) Propane can be cracked to form ethene and methane.
C3H8(g) C2H4(g) CH4(g)
The standard enthalpy change of combustion of ethene, Hc = –1410 kJ mol-1.
Use this value together with relevant values in Table above to calculate the enthalpy change of this reaction.
H = ......................... kJmol-1
[3]
[Total 7 marks]
16. The carbonates and nitrates of Group 2 elements decompose when heated.
Barium nitrate decomposes when heated to make barium oxide, nitrogen dioxide and oxygen.
2Ba(NO3)2(s) → 2BaO(s) + 4NO2(g) + O2(g)
Calculate the enthalpy change of reaction, ∆Hr, in kJ mol–1, for the thermal decomposition of barium nitrate using the enthalpy changes of formation, ∆Hf, given in the table.
compound ∆Hf /kJ mol–1
Ba(NO3)2(s)
BaO(s)
NO2(g) –992
–558
+33
answer ........................... kJ mol–1
[3]
[Total 3 marks]