Question

Determine the enthalpy of reaction for 2ch₄(g) → c₂h₄(g) 2h₂(g) using the equations: 2c₂h₄(g) 7o₂(g) → 4co₂(g) 6h₂o(l) Δh° = -3120.8 kj/mol ch₄(g) 2o₂(g) → co₂(g) 2h₂o(l) Δh° = -890.3 kj/mol c₂h₄(g) h₂(g) → c₂h₄(g) Δh° = -136.3 kj/mol h₂ ½o₂(g) → h₂o(l) Δh° = -285.8 kj/mol?

Answer 1

Using Hess's law and the given equations, we can determine the enthalpy of reaction for 2CH₄(g) → C₂H₄(g) + 2H₂(g) to be -787.0 kJ.

Step-by-step explanation:

We can use Hess's law to determine the enthalpy of reaction for 2CH₄(g) → C₂H₄(g) + 2H₂(g). By writing and combining the given equations, we can find the enthalpy change for the desired reaction.

First, we reverse equation (1) to obtain 2CO(g) → 2C(s) + O₂(g) with an enthalpy change of +221.0 kJ. Next, we use equation (2) as written: C(s) + O₂(g) → CO₂(g) with an enthalpy change of -393.5 kJ/mol. Multiplying equation (2) by 2 to get 2C(s) as the reactant, we find that the enthalpy change is -393.5 kJ/mol.

Finally, we add the two equations and their enthalpy changes together to obtain the desired reaction: 2C(s) + 2O₂(g) → 2CO₂(g) with an enthalpy change of -787.0 kJ.