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Offline peterschmidt3943

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Volume reacting
« on: December 13, 2017, 10:45:53 AM »
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 ?
« Last Edit: December 14, 2017, 04:42:46 AM by sjb »

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Re: Volume reacting
« Reply #1 on: December 13, 2017, 11:18:30 AM »
Do you know what the limiting reagent is?
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Offline peterschmidt3943

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Re: Volume reacting
« Reply #2 on: December 13, 2017, 11:19:29 AM »
yes, I do. In this case, F is the limiting reactant, right?

Offline peterschmidt3943

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Re: Volume reacting
« Reply #3 on: December 13, 2017, 11:57:22 AM »
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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Re: Volume reacting
« Reply #4 on: December 13, 2017, 02:00:50 PM »
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?

Quote
leaving 10cm^2

10 mL of what?

Quote
But since we produced 20cm^2

20 mL of what?

Quote
we got in total 30cm^2 left , right ?

30 mL of what?
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Offline peterschmidt3943

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Re: Volume reacting
« Reply #5 on: December 13, 2017, 02:15:48 PM »
20ml of F
leaving 10ml of Xe
20ml of XeF2
total gas amount left in the syringe: 30ml
respectively...

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Re: Volume reacting
« Reply #6 on: December 13, 2017, 02:23:28 PM »
Looks OK.
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Offline peterschmidt3943

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Re: Volume reacting
« Reply #7 on: December 13, 2017, 02:32:07 PM »
Yes, but why do we claculate with the values from the limiting reagant?

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Re: Volume reacting
« Reply #8 on: December 13, 2017, 02:50:59 PM »
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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Offline Enthalpy

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Re: Volume reacting
« Reply #9 on: December 13, 2017, 07:23:57 PM »
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.

Offline sjb

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Re: Volume reacting
« Reply #10 on: December 14, 2017, 01:43:55 AM »
Citing https://en.wikipedia.org/wiki/Xenon_difluoride...

True but I don't think this is quite relevant to the actual question?

Offline Enthalpy

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Re: Volume reacting
« Reply #11 on: December 14, 2017, 08:46:53 AM »
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.

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