Question Video: Converting between Energy per Molecule and Energy per Mole Chemistry • 10th Grade

3.70 mol of Cl-Cl bonds release 888 kJ of energy when they form. How much energy is released when 1000 Cl-Cl bonds form?

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Video Transcript

3.70 mole of Cl–Cl bonds release 888 kilojoules of energy when they form. How much energy is released when 1000 Cl–Cl bonds form?

We want to know the energy that’s released when 1000 Cl–Cl bonds are formed. But we’re given the energy released when 3.70 moles of Cl–Cl bonds are formed. So let’s first find the energy released when one Cl–Cl bond is formed. And then we can find the energy that’s released when 1000 Cl–Cl bonds are formed. We know that 888 kilojoules of energy is released per 3.70 mole of Cl–Cl bonds. We also know that one mole is equivalent to 6.022 times 10 to the 23. We can multiply by this equivalency to find the energy released per mole of bonds because there will be 6.022 times 10 to the 23 bonds in one mole of bonds. Multiplying everything through we’ll find that there is 3.98538 times 10 to the minus 22 kilojoules of energy released per Cl–Cl bond formed.

Now, to find the energy that is released when 1000 Cl–Cl bond formed, we simply need to multiply this number by 1000. That gives us 3.98538 times 10 to the minus 19 kilojoules. Now, this is a very small number. So maybe it’s better to express it in joules. Since there are 1000 joules in a kilojoule, we can convert to joules by multiplying by 1000. This gives us 3.98538 times 10 to the minus 16 joules. Finally, both the moles and the energy was given to three significant figures. So our answer should be given to three significant figures as well. Now, we have our final answer of 3.99 times 10 to the minus 16 joules of energy that is released when 1000 Cl–Cl bonds are formed.