MediumChemistryHigh School (11–12)Chemical Bonding › Shapes of Molecules and HybridisationNumericalBoard Exam
In ethane, ethene and ethyne, the carbon atoms are sp³, sp² and sp…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In ethane, ethene and ethyne, the carbon atoms are , and . Find the s-character of each kind of hybrid. The C-H bonds are about , and long, in no special order. Match each length to its molecule, and explain.
Need a reminder? The key ideaShow
Hybridisation mixes atomic orbitals of nearly equal energy into the same number of equal hybrid orbitals. Two pairs on the central atom give sp (180°), three give sp2 (120°), four give sp3 (109.5°), five give sp3d (trigonal bipyramidal) and six give sp3d2 (octahedral). The s-character of each hybrid is 100% divided by the number of orbitals that mix. Unhybridised p orbitals form pi bonds.
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. s-character. : . : . : .
Step 2. The idea. More s-character keeps the hybrid closer to the nucleus. So the bond it makes is shorter.
Step 3. Matching. Ethyne () has the shortest C-H bond, . Ethene () has , and ethane () .
Answer: , and ; the C-H bond is shortest in ethyne and longest in ethane.
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