Problem E7

[Ellen Tsai 3D]

I got the answer right but I'm confused why we are diving the population of people by Avogadro's number instead of multiplying it. Thanks!

[Chris Oh 2I]

For problem E7 (the atoms of Carbon question), you divide instead of multiply due to dimensional analysis.

Since there are 2.1 x 10^9 atoms carbon, to convert it into moles you must multiply 2.1 x 10^9 atoms carbon by (1 mole carbon / 6.022 x 10^23 atoms carbon), which is basically dividing by Avogadro's constant. I hope this helps!

[Aaron Li 1D]

If you're talking about population of people then I think you're referring to problem E5, which wasn't assigned. However, for problem E7, since the number of atoms are given instead of number of moles, you would need to solve backwards. Since there are 6.0221 x 10^23 atoms per mole (Avogadro's number), you would need to divide the number of atoms by Avogadro's number to get the number of moles of carbon found in DNA. If you were given a value in moles and need to find the number of atoms, then you would multiply with Avogadro's number.