Grams, moles, and N atoms?

Question

C7H5(NO2)3

How can I find out the number of grams, number of moles, and number of N atoms, by only knowing that there are 1.24x10^28 molecules?

Any help is greatly appreciated!!

Answer 1

The molecular mass is: 7*12 + 5*1 + 3(14 + 2*16) = 227.

I'll work backwards on your questions.

There are 3 nitrogen atoms in every C7H5(NO2)3 molecule. So number of N atoms in 1.24x10^28 molecules is 3x1.24x10^28 = 3.72x10^28 N atoms.

There are 6.02x10^23 particles per mole approximately. So there are (1.24x10^28)/(6.02x10^23) = 2.06x10^4 moles.

One mole has a mass of 227 grams. So 2.06x10^4 moles has a mass of 2.06x10^4 x 227 = 4.68x10^6 g = 4.68x10^3 kg.