Mass of a Carbon-12 atom - Please Help!?

Question

Calculate the mass, in grams, of 1 atom of carbon-12 .... of nitrogen-14.... of fluorine-19. (Assume that the mass number of these isotopes is equal to the atomic mass, rounded to the nearest whole number.)

Answer 1

That's a pretty rough estimate of the actual molar mass of an isotope.  It's easy enough to look up the actual mass of any isotope.

Select the "isotopes" tab at the following, then click on any element in the table and you will get a box for each isotope along with its actual mass.

http://www.dayah.com/periodic/

Divide the mass of the isotope by Avogadro's number to get the mass of single atom of that isotope.

Mass of C-12 is easy, since masses for the entire periodic table are based on the mass of C-12 being exactly 12.0000... g/mol.

mass of N-14 = 14.00307 g/mol

14.00307 g / mol x (1 mol N / 6.022 x 10^23 atoms) = 2.3243 x 10^-23 g / atom

Answer 2

You want the mass of a single atom of each of those?

Just divide the mass number by 6.02x10^23.

So for carbon-12 it's 12/6.02x10^23. Use your calculator to figure out what that is. Same for the rest.