Asample of c3h8 has 4.00 × 1024 h atoms.
how many carbon atoms does the sample contain?

this is the one im mainly confused about: what is the total mass of the sample?

Hi Menrique,

C3H8 is propane, which is a molecule that combines carbon and hydrogen atoms in a ratio of 3:8. Put simply, for every 8 molecules of hydrogen there will be three atoms of carbon.

So, if there are a total of 4.00 x 1024 or (4096) hydrogen atoms present, then the number of carbon atoms will be:

C = 3/8 (H)
C = 3/8 (4096)
C = (3 x 4096) / 8
C = 1536

So, there would be 1,536 carbon atoms present if there are 4096 hydrogen atoms.

The total mass of the sample is a bit more involved. You'll need to use Avagadro's number to determine it.

First, calculate the mass of one mole of C3H8. Since carbon has an atomic weight of roughly 12 and hydrogen roughly 1, the mass of one mole of C3H8 = (12 x 3) + (1 x 8) = 36+8 = 44 grams.

Next, recall that one mole of any pure substance contains 6.022 x 10^23 molecules.

So, one mole of propane (C3H8) has a mass of 44 grams and contains 6.022 x 10^23 molecules. Using this, you can now determine the mass of the specimen.

If there are 4096 hydrogen atoms present, then the total number of propane molecules is 4096 / 8 = 512, since each propane molecule requires a total of eight hydrogen molecules.

Now, if 6.022 x 10^23 molecules = 44 grams, then 512 molecules would equal:

44 g / 6.022 x 10^23 = x / 512

Cross multiply and solve for x, which is going to be very, very small...

Good luck!