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MCAT Question A Day - 4/22/13 - Answer!

As the multiplicity of bonds increases, the

A.  bond energies increase and bond lengths decrease.
B.  bond energies and lengths both decrease.
C.  bond energies and lengths both increase.
D.  bond energies decrease and bond lengths increase.

The correct answer is (A). Single bonds contain one sigma bond while double and triple bonds have one and two pi bonds, respectively, in addition to the sigma bond. The energy required to break these bonds, i.e., the bond dissociation energy, increases as the number of bonds increases. As the number of bonds between atoms increases, the atoms are pulled closer together and the bond length decreases.