Question

Would you mind checking these mole/unit conversion problems over? I understood them in class today, but that was hours ago, so now I need to start all over again.

How many moles of GaBr3 are in 983 grams? I got 983g times 1mole/309.42, which equaled 3.18. Is this correct? If not, could you explain the correct way?

One more. How many molecules are in 3.4 grams of H2? I set up the proportion so it read: 3.4 grams times 1 molecule/2 grams.

Thanks for your explanations.

Answer 1

#1 is correct.
#2 is not but you're half way there.
3.4 g H2 x (1 mole H2/2 g H2) = 1.7 moles H2. Now convert that to molecules. You must remember that 1 mole of H2 is 2 grams of H2 (or 22.4 L of the gas) but a mole and a molecule are not the same thing. 1 mole of H2 contains 6.02 x 10^23 molecules.

Answer 2

Thanks for the explanation. WOuld the answer then be 10.23?

Answer 3

hardly 10.23.
3.4 g H2 x (1 mole H2/2.016 g H2) x (6.022 x 10^23 molecules H2/1 mole H2) = 1.016 x 10^24 which rounds to 1.0 x 10^24 to two significant figures.