Asked Nov 1, 2019

Use standard enthalpies of formation to determine ΔHorxnfor:

2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l)

Enter in kJ.

Find the change in internal energy for this reaction. Enter in kJ.



Expert Answer

Step 1

Standard enthalpy of formation is defined as the amount of heat absorbed or evolved in the formation of mole of a compound from its constituent elements in their standard states.

The required reaction is written as follows:

2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(l)


The enthalpies of formation values of the given compounds are as follows:


Image Transcriptionclose

AH°CH (g)-226. 73 kJmol" AH,°O (g) 0 kJmol AH, HO(1)-285.83 kJmol "1 AH,CO, (g)-393.51 kJmol-

Step 2

The expression for the determining the enthalpy change of reaction is shown as equation (1).


Substitute the values of enthalpy change of formation of the given compounds to calculate the enthalpy change is shown as equation (2).


Image Transcriptionclose

AH° AH, (products)- AH,°(reactants) 4 mol(AH,(Co, (8) +2mol (AH, (H2O(1) -2 mol (AH,°(CH (s))) +5 mol (AH,°(02(8)) (1) AH4 mol-393.5 kJmol)+2 mol(-285.9 kJmol 2mol(226.73 kJmol")+5 mol (0 kJmol AH1574.04 kJ-571.66 kJ]- [453.46 kJ] (2) AHo2599.16 kJ

Step 3

The expression for change in internal energy is written below.

∆U = ∆H - ∆ngRT

Here, ∆U is change in internal energy, ∆H is the change in enthalpy, &n...

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