Mole calculation (work check)

[jimmyp]

For the element bromine, Br:
(a) Calculate the number of moles in 5.07 g.
(b) Calculate the number of grams in 0.238 mol.
(c) How many moles are there in 4.94 x 1022 atoms of the element?


(a) Here is my solution:

5.07g Br * 1 mole Br / 79.90g Br = 0.0635 moles Br

(b) Here is my solution:

0.238 mole Br * 79.90g Br / 1 mole Br = 19.0g Br

(c) I am unsure how to do this? What are the steps I need to do?


Is my a-b correct?

Thanks for reading. :)

[Sonic]

For the element bromine, Br:
(a) Calculate the number of moles in 5.07 g.
(b) Calculate the number of grams in 0.238 mol.
(c) How many moles are there in 4.94 x 1022 atoms of the element?


(a) Here is my solution:

5.07g Br * 1 mole Br / 79.90g Br = 0.0635 moles Br

(b) Here is my solution:

0.238 mole Br * 79.90g Br / 1 mole Br = 19.0g Br

(c) I am unsure how to do this? What are the steps I need to do?


Is my a-b correct?

Thanks for reading. :)

Yes, a and b are correct. I've not checked your arithmetic but your workings are correct.

For part c recall the Avogadro Constant: 6.02*10^23 molecules/mole and divide the number you have by it

[jimmyp]

Thus I can write:

(4.94 * 10^22 Br atoms) * (1 mole Br / 6.022 * 10^23 Br atoms) = 0.0820 moles Br


Correct?

[Sonic]

Thus I can write:

(4.94 * 10^22 Br atoms) * (1 mole Br / 6.022 * 10^23 Br atoms) = 0.0820 moles Br


Correct?

That's exactly right :)