Calculate the change in the enthalpy of the reaction.

C4H4(g)+2H2(g)===>C4H8(g)

Use the following:
change in enthalpy of combustion for: C4H4=-2341 kJ mol-1
H2=-286 kJ mol-1
C4H8=-2755 kJ mol-1

Your question isn't clear. I assume one equation is

C4H4 + O2 ==>CO2 + H2O
but I don't now what H2 = ?? and C4H8 = ?? mean.

Umm... the H2 is hydrogen and C4H8 is Carbon 4, Hydrogen 8. If I knew what it meant than I wouldn't be asking for help, would I?!?!?

Answere

To calculate the change in enthalpy (ΔH) of the given reaction, you can use the concept of Hess's Law. According to Hess's Law, the change in enthalpy for a chemical reaction can be determined by the difference in enthalpy between the products and the reactants.

The given reaction is:
C4H4(g) + 2H2(g) → C4H8(g)

To find the change in enthalpy for this reaction, you can consider the combustion reactions of individual components.

1. The combustion reaction for C4H4 is given as -2341 kJ/mol. This means that 1 mol of C4H4 releases 2341 kJ of energy when it is completely burned in oxygen.

2. The combustion reaction for H2 is given as -286 kJ/mol. This means that 1 mol of H2 releases 286 kJ of energy when it is completely burned in oxygen.

3. The combustion reaction for C4H8 is given as -2755 kJ/mol. This means that 1 mol of C4H8 releases 2755 kJ of energy when it is completely burned in oxygen.

Now, we need to rearrange the given reaction so that it matches the combustion reactions of the components.

C4H4(g) + 4H2(g) → C4H8(g)

By rearranging the coefficients of H2, we can see that 4 moles of H2 are required in the reaction to produce 1 mole of C4H8.

Using this, we can determine the change in enthalpy for the given reaction.

ΔH = (2 × -2341 kJ/mol) + (4 × -286 kJ/mol) - (-2755 kJ/mol)

ΔH = -4682 kJ/mol + (-1144 kJ/mol) + 2755 kJ/mol

ΔH = -3071 kJ/mol

Therefore, the change in enthalpy of the reaction is -3071 kJ/mol.