Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: peterschmidt3943 on December 13, 2017, 10:45:53 AM
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30 cm3 of xenon are mixed with 20 cm3 of fluorine. The gases react according to
the following equation.
Xe(g) + F2(g) → XeF2(g)
Assume that the temperature and pressure remain constant.
What is the final volume of gas after the reaction is complete?
I have a problem with this question. We know that 20cm^3 react with 30cm^3. But does that mean that 20cm^3 react ? Because we got 2*F, we got 10cm^3 of fluorine reacting with 10cm^3 with Xe, right ?
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Do you know what the limiting reagent is?
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yes, I do. In this case, F is the limiting reactant, right?
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and since F is the limiting reactant, we got 20 cm^2 used up, leaving 10cm^2. But since we produced 20cm^2, we got in total 30cm^2 left , right ? If yes, i do not know why we have to calculate everything with the values from the limiting reactant. Why does one mole of the limiting reactant equal 1 mole of Xe, or XeFe2 ?
Kind regards
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First of all - no, we don't work with square centimeters, we work with volume, not surface. But I assume it is just a typo.
we got 20 cm^2 used up
20 mL of what?
leaving 10cm^2
10 mL of what?
But since we produced 20cm^2
20 mL of what?
we got in total 30cm^2 left , right ?
30 mL of what?
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20ml of F
leaving 10ml of Xe
20ml of XeF2
total gas amount left in the syringe: 30ml
respectively...
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Looks OK.
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Yes, but why do we claculate with the values from the limiting reagant?
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Because one of the reagents limits the reaction. I will rephrase my question: do you understand what the limiting reagent is?
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Citing https://en.wikipedia.org/wiki/Xenon_difluoride
Xenon difluoride is a dense, white crystalline solid.
It has a low vapor pressure.
Vapor pressure 6.0×102 Pa
Melting point 128.6 °C (no boiling point given)
In addition, the reaction needs conditions that decompose the product too, so can the reaction be complete?
Looks like the question's conditions are strongly idealized.
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Citing https://en.wikipedia.org/wiki/Xenon_difluoride...
True but I don't think this is quite relevant to the actual question?
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Because students keep in mind for decades some claims and assumptions of their assignments, these should be correct. And it is important to debunk them when wrong.