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Equation question!

Could someone please help on the equation question in the image attached please!

What is the answer and why? I really don't get it!

Thanks!
Screen Shot 2017-05-02 at 17.13.24.png89.7KB
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Avatar for S.G.
S.G.
22
Original post by dp00
Could someone please help on the equation question in the image attached please!

What is the answer and why? I really don't get it!

Thanks!


I think D. Use the formula n=V(cm3)/24000
Reply 2
Avatar for _NMcC_
_NMcC_
15
Original post by dp00
Could someone please help on the equation question in the image attached please!

What is the answer and why? I really don't get it!

Thanks!


You don't actually need to use n=V/24 in this case.

Understand that the 30cm3 of Xenon is in excess (as the mole ratio is 1'1'1, so there'll be 10cm3 unreacted Xe as a product) and 20cm3 fluorine is the limiting reagent or the one which limits how much material reacts.

As a rule of thumb, the reagent in lesser quantity is generally the limiting reagent however be careful as sometimes the mole ratios can say otherwise. Always use the mole conversion equations if you are unsure (n=V/24 etc) or with more complex mole ratios or stoichiometry.

So 30cm3 reacting with 20cm3 in a 1'1'1 ratio will always mean that only 20cm3 of product will be formed with 10cm3 unreacted Xe (which is why it's said to be in excess, there's excess left over.)
(edited 6 years ago)

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