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Chemistry Question Help please

Can anyone tell me the answer to this question, it would be greatly appreciated.

Fluorine reacts with sulfur to produce sulfur hexafluoride.

S + 3F(little two) --------> SF(little six)

Relative formula masses, F(little two) = 38 SF(little six) = 146

Calculate the mass of sulfur hexafluoride produced when 0.950 g of fluorine is reacted with an excess of sulfur.

Give your answer to 3 sig figs.
Work out moles of Flourine (Mass/Mr = Moles)
Work out moles of SF, the product by dividing/multiplying according to the molar ratio (In this case divide by 3 as the ratio is 3:1)
Work out mass of SF produced (Mass = Moles times Mr)

I'd suggest watching this if you're confused : https://www.youtube.com/watch?v=TV6n5MFH6IU&ab_channel=Freesciencelessons
Reply 2
Thanks for the reply! I did get an answer of 1.22g but i'm not sure if that's correct. Could you possibly check to see what the correct answer is?
Original post by cj_sS
Thanks for the reply! I did get an answer of 1.22g but i'm not sure if that's correct. Could you possibly check to see what the correct answer is?


Yep, seems good. Well done :smile:
Reply 4
Cheers mate
First you work out the number of moles in fluorine. You don't need to worry about sulphur as it is in excess, (so loads is available - think of it as an infinite amount available for you.).

To work out number of moles, you require the formula:

moles = mass / molar mass

I see you have correctly worked out molar mass for fluorine, which is 38.
Mass is given to you, so you plug it in the formula.
When you divide 0.950 by 38, you get 0.025 moles.
According to stoichiometry, for 3 fluorine molecules, you have 0.025 moles
But Sulphur hexafluoride, has 1 mole in front of it.
So you need divide 0.025 by 3 to find amount of moles for 1, which is 8.333333333*10^-3 moles
I see you have correctly worked out molar mass for sulphur hexfluoride, which is 146.1
Again, using the same formula, rearrange to make mass the subject, which is mass= moles * molar mass
You have molar mass and moles, hence plug it in, so 8.333333333*10-3 multiplied by 146.1 is 1.2175g
That is the amount of sulphur hexafluoride produced
You said 3 s.f., so you would answer as 1.22g
Reply 6
Original post by neluxsan
First you work out the number of moles in fluorine. You don't need to worry about sulphur as it is in excess, (so loads is available - think of it as an infinite amount available for you.).

To work out number of moles, you require the formula:

moles = mass / molar mass

I see you have correctly worked out molar mass for fluorine, which is 38.
Mass is given to you, so you plug it in the formula.
When you divide 0.950 by 38, you get 0.025 moles.
According to stoichiometry, for 3 fluorine molecules, you have 0.025 moles
But Sulphur hexafluoride, has 1 mole in front of it.
So you need divide 0.025 by 3 to find amount of moles for 1, which is 8.333333333*10^-3 moles
I see you have correctly worked out molar mass for sulphur hexfluoride, which is 146.1
Again, using the same formula, rearrange to make mass the subject, which is mass= moles * molar mass
You have molar mass and moles, hence plug it in, so 8.333333333*10-3 multiplied by 146.1 is 1.2175g
That is the amount of sulphur hexafluoride produced
You said 3 s.f., so you would answer as 1.22g


Great, thanks a lot for the thorough explanation - i really appreciate it!
Original post by cj_sS
Great, thanks a lot for the thorough explanation - i really appreciate it!


N0 :smile: glad to help
I meant np
I am not because none of you make sense. I am only in yr 10 and have tried your method but when i do 0.025/3 i get 0.00833333333333333333333333333333 which is not what you got! I am realllllllyyyyy stuckkkkkkkkkk :'(

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