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Moles question - help needed!

I HATE moles and I never understand how to use them. This is the question:

Sodium reacts with sulphur to form sodium sulphide:

2Na + S --> Na2S

An 11.5g sample of sodium is reacted with 10g of sulphur. All of the sodium is reacted but there was an excess of sulphur.
Calculate the mass of sulphur left unreacted.

(i) Number of moles of sodium atoms reacted =
[2 moles of Na react with 1 mole of S]
(ii) Number of moles of sulphur atoms that reacted =
(iii) Mass of sulphur reacted =
(iv) Mass of sulphur left unreacted =

Thank you.

Reply 1

Christophicus

(i) Amount of sodium that reacted = 11.5/23 = 0.5 moles
(ii) Amount of sulphur that reacted = 0.25 moles (you can see this from the equation) - [2 moles of Na react with 1 mole of S] so the amount of sulphur that reacted is half the amount of sodium that reacted. Don't confuse amount with mass though. Amount refers to the number of moles.
(iii) Mass of sulphur reacted = 0.25 x 32 = 8 grams of sulphur.
(iv) Mass of sulphur left unreacted = 10g - 8g = 2 grams unreacted