E.7 Chemical Principle 7th edition

[Ziyan Wang 3J]

A molecule of human DNA was found to contain 2.1 * 10^9 atoms of carbon. Calculate the chemical amount (in moles ) of carbon atoms in the molecule of DNA.

[Samuel Tzeng 1B]

3.5*10^-15 moles of Carbon

[Chem_Mod]

Recall Avogradro's number is 6.022 x 10^23. In this problem, you're given 2.1 x 10^9 atoms of carbon, so divide by Avogadro's to find the number of moles.

If you're still having trouble understanding the above step, then I would recommend attending Step-Up sessions.

[Jenna Ortiguerra 4G]

The question is asking you to calculate the amount of carbon ATOMS in the molecule of DNA. To convert atoms into moles, you use Avogadro's number (6.022*10^23).

(2.1*10^9 atoms) * ((1molC)/(6.022*10^23 C)) = 3.5*10^-15 moles C

The amount of moles in carbon is 3.5 * 10^-15 moles C

[Montana James 4G]

The above responses are perfect, but for conversion questions in general it may also be helpful to think of Avogadro's number as 6.022 x 10^23 "things" (be it atoms, molecules, etc.) in one mole. From there it makes it easier to see what you need to divide or multiply.