Video: Calculating the F—F Bond Energy from the Molar Bond Energy of F₂ Using Avogadro’s Number

The molar bond energy of F₂ is 159 kJ/mol. Calculate the energy of one F–F bond.

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Video Transcript

The molar bond energy of F two is 159 kilojoules per mole. Calculate the energy of one F–F bond.

The molar bond energy is the energy needed to break a chemical bond per mole of bonds. This means that it must take 159 kilojoules of energy to break one mole of F–F bonds. But we’re working for the energy of one F–F bond. We should be able to find the energy of one F–F bond by dividing the energy of one mole of F–F bonds by one mole.

The energy of one mole of F–F bonds is 159 kilojoules. One mole is always equivalent to 6.022 times 10 to the 23 of something, in this case bonds. So we should divide by 6.022 times 10 to the 23. This gives us 2.6412 times 10 to the minus 22 kilojoules. Since the molar bond energy was given to three significant figures, our answer should be given to three significant figures as well. So we get an answer of 2.64 times 10 to the minus 22 kilojoules.

Now our kilojoules are a perfectly appropriate unit to express our answer in. This is a very small amount of energy. So let’s convert our answer to joules. Since there 1000 joules in a kilojoule, we can convert to joules by multiplying by 1000, which gives us 2.64 times 10 to the minus 19 joules, which is the energy of one F–F bond.

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