TBR Chem Chap 6 #83 - Gas volume calculations

[loveoforganic]

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I'm pretty sure this is a TBR mistake in what they've made expected by the problem vs what they're trying to test - if anyone could verify or say what I'm not seeing that'd be great!

The question is "What is the volume of fluoromethane at 25 oC and 1.00 atm?" with answer choices being

A) 20.17 L
B) 22.41 L
C) 24.24 L
D) 32.17 L

The gist of the passage is getting you to compare real and ideal gases (with this being a real gas obviously).

To go from STP volume of 22.4 L/mol ideal gas to the conditions given, you need the conversion 22.4*(298/273), which I don't see a way to approximate with high accuracy (contradictory I know, but you need pretty accurate results to judge between B and C). Is there a quick way to do the math that I'm not seeing?

 

[tttgo]

isn't choice b for ideal since it's at 22.4? can't you just eliminate it right away?

 

[Rabolisk]

It seems like simple math to me. 22.4 * 298/273 is closer to 22.41 or 24.24? 298/273 is a jump of 25 degrees from 273, which is like increasing by 10% (25/273 = 0.1 roughly). Increasing 22.4 by about 10% yields 24.24, rather than 22.41.

The real deviation from ideal is not enough to explain any other choices for any gas at this pressure and temperature. Pressure is too low and temperature is high enough.

 

[loveoforganic]

isn't choice b for ideal since it's at 22.4? can't you just eliminate it right away?

If the temperature was 1 oC, could you eliminate it?

It seems like simple math to me. 22.4 * 298/273 is closer to 22.41 or 24.24? 298/273 is a jump of 25 degrees from 273, which is like increasing by 10% (25/273 = 0.1 roughly). Increasing 22.4 by about 10% yields 24.24, rather than 22.41.

The real deviation from ideal is not enough to explain any other choices for any gas at this pressure and temperature. Pressure is too low and temperature is high enough.

Thanks, I guess I'm just too far removed from having learned it to remember what reasonable changes in volume due to realness are - wasn't sure if a couple liters was extreme or not.

Btw, are you a Phd/ms chemist rabo? I'm a regular on chemicalforums as well and saw you listed yourself as a chemist there, which coincides well with your explanations here.