Estimate Δr H for C₂H₄(g) + H₂(g) → C₂H₆(g) from the mean bond enthalpies: C=C 611, H-H 435, C-C…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Estimate for from the mean bond enthalpies: C=C , H-H , C-C and C-H , all in kJ/mol. Which bonds are broken and which are formed?
Need a reminder? The key ideaShow
Hess's law: the enthalpy change of a reaction is the sum of the enthalpy changes of any set of steps that lead from the same start to the same end. Equations add like algebra: reverse one and its changes sign, multiply one and its is multiplied. For gases, , using mean bond enthalpies.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Broken. One C=C and one H-H: .
Step 2. Formed. One C-C and two new C-H: .
Step 3. Estimate. .
Answer: about , exothermic.
Discussion (0)
Log in to join the discussion.
Loading…