Hess' Law (From Kognity)

Calculate the enthalpy change of formation ΔH_f, in kJmol^-1, of ethyne (C₂H₂), given the following data.

Give your answer rounded to 3 significant figures (no units required). 

The combustion of propane occurs by the following reaction.

C₃H₈(g) + 5O₂(g) → 3CO₂(g)+ 4H₂O (l)

ΔH=?

You have the following formation equations for which Hess’s Law can be used to calculate the enthalpy of combustion, in kJ mol^-1, for propane. (No units required in your answer.)

The equation for the formation of ethene from its elements is shown below: 

2C (s) + 2H₂ (g) → C₂H₄ (g)

Determine the standard enthalpy of formation of ethene, ΔH_f, in kJ mol^-1, given the following three equations and their enthalpy change of combustion values, ΔH_c. Give the answer to two significant figures (no units required). 

Calculate the standard enthalpy of formation, ∆H^Ɵ_f ,  of ethanoic acid, CH₃COOH(l), 

2C(s) + O₂(g) + 2H₂(g) →  CH₃COOH(l)      ∆H^Ɵ_f = ? kJ mol^-1 

given the following data in table.

Give the answer to 3 significant figures (no units required). 

In the energy cycle below for calculating the enthalpy of formation of propanoic acid, what type of enthalpies have been provided on the arrows?

• enthalpies of formation

• enthalpies of combustion

• enthalpies of neutralisation

• enthalpies of ionisation