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Topic: Question about solving for volume  (Read 5915 times)

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Offline 1337monk

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Question about solving for volume
« on: January 01, 2008, 08:12:08 PM »
How much volume does .10 mole of hydrogen occupy at STP? I am confused on how you turn the moles into volume.

Offline 1337monk

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Re: Question about solving for volume
« Reply #1 on: January 01, 2008, 08:18:53 PM »
i think i figured it out at 1.123mL is this correct?


and  1mL = 1cm3 correct?

Offline Alpha-Omega

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Re: Question about solving for volume
« Reply #2 on: January 01, 2008, 08:25:17 PM »
You do not turn moles into volume.  A mole is a quantity of a substance.  OK when I teach this I get the point across this way:

How many roses are in a dozen roses?  12 right
How many tires are in a dozen tires?  12 right
How many eggs in a dozen eggs?  12 right

So a mole contains exactly 6.022 x 10^23 objects or things.

A mole of tires has 6.022 x 10^23 tires
A mole of roses contains 6.022 x 10^23 roses
A mole of eggs has 6.022 x 10^23 eggs
A mole of ions has 6.022 x 10^23 ions in it
A mole of atoms has 6.022 x 10^23 atoms.....Do you get it????

Now for your chemistry problem you need to apply the Ideal Gas Law and the rule that a 1 mole of an ideal gas occupies a volume of 1 Liter at STP....

Here you do not have 1.0 mole you have 0.1 mole of gas and you have STP  and STP means standard temperature and pressure....25 C and 1 atm...use appropriate units.

Look at the data they give you...write down what STP iis:  they are specified temperature and pressure conditions....then look at the moles they give....it is not 1.0...it is a factor of 10 less it is 0.10 mole of hydrogen.

Use PV = nRT

Rearrange:  V = (nRT/P)

Plug in your data and solve.....make sure all your units are in the same system..

Offline Alpha-Omega

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Re: Question about solving for volume
« Reply #3 on: January 01, 2008, 08:31:00 PM »
OK...1 mL = 1 cm^3....that is correct.

I cannot answer the rest without seeing all the units you used in the equation.  Set up the equation with all the correct units and cancelling everything should leave you with VOLUME.   If you are reporting it in mL   you will be left only with mL in the equation.

Offline Borek

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Offline Borek

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Re: Question about solving for volume
« Reply #5 on: January 01, 2008, 08:42:21 PM »
Now for your chemistry problem you need to apply the Ideal Gas Law and the rule that a 1 mole of an ideal gas occupies a volume of 1 Liter at STP...

I am sure it is a typo ;)

22.4 L if anything. Problem is, nobody really knows what STP means.

http://en.wikipedia.org/wiki/Standard_conditions_for_temperature_and_pressure
« Last Edit: January 16, 2012, 03:02:22 PM by Arkcon »
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Offline Alpha-Omega

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Re: Question about solving for volume
« Reply #6 on: January 01, 2008, 08:46:51 PM »
OOPS yes sorry about that

Offline 1337monk

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Re: Question about solving for volume
« Reply #7 on: January 01, 2008, 09:01:14 PM »
thank you all for the H-E-L-P!  ;D

i think i got it now it occupies 2.351 L

STP - 273k   1 atm   .0861((L*atm)/(mol*k))

Offline Alpha-Omega

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Re: Question about solving for volume
« Reply #8 on: January 01, 2008, 09:15:14 PM »
OK...not being picky....but R = 0.0821 when using L·atm·K-1·mol-1

So I get V = 0.1 (0.0821) (273)/1 = 2.24L   which makes sense since 1 mole occupies 22.4 L then .1 mole occupies 10 times less the volume or 2.24L

Have to redeem myself for that TYPO....MY BAD....

Offline Alpha-Omega

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Re: Question about solving for volume
« Reply #9 on: January 01, 2008, 09:21:18 PM »
What you should be seeing from this problem is that NO MATH was required....and that P-Chem is SO EASY...all you need to know for basics are the units and the contants....you just had to know the rule that at STP 1 mole of any Ideal gas occupies 22.4L....so if you have 0.1 mole which is 10 times less moles than 1 mole it will occupy 10 times less volume or 2.24L.

Do you see how simple just move the decimal point to the left one place....

REDEEMED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ;D

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