Gas standards?

[Rosin]

Hello,

My questions is regarding the standard on temperature and pressure. I'm uncertain on which ones IB uses.

I have read in the Pearson Baccalaureate HL Chem, it says the standards are:

STP - 273K at 100kPa

RTP - 298K at 100kPa

However, my teacher tells me it's:

STP - 273K at 101.3kPa (1atm)

SATP - 298K at 100kPa

Which one is right? Or are they both wrong?

Thank you!

[ILM]

the both are right. But they give you pressure and tempreture at different situation.

the first one which is STP is at standard tempreture and pressure ( when t=0 C and pressure= 1 atm) if you convert Celsius to kelvin it will be at t=273 and p=1atm=101.3 kpa at that situation the volume of one mole of gas is 22.4L. in ib they will usually state that the question should be answered at STP situation.

the second one is at room situation, in which t= 25 C and p= 1 atm, t=25 C= 298 kelvin. the volume of 1 mole of gas at RTP is 24 L. SATP is the same but with another more scientific name it stand for Standard Ambient Temperature and Pressure

So as you can it is only a two different usuall situations, but both are right.

Don't hesitate if you have any further considerations.

Good luck

Edited April 12, 2011 by inm

[Rosin]

So, STP should be 101.3 kPa at 273K and not 100 kPa at 273K? Or is it that either can be used for the definition of STP? Just depending on the context.

And RTP and SATP can be used interchangeable?

Thanks.

[ILM]

it depends on the significant figures that you want your answer to be to, so it depends on the context.

for rtp and Satp yea they the same meaning.

[Keel]

Physicists are weird people and they like to work at 0^oC and use strange units such as pascals, whereas we chemists are very practical and work at room temperature. So the standard environment is in fact:

Temperature: 25^oC or 298K

Pressure: 1 atm

(Concentration: 1M) standard electrode potentials: ion concentration

So in the exam or any other chemistry situation, always use the above and not anything else.

[Rosin]

Physicists are weird people and they like to work at 0^oC and use strange units such as pascals, whereas we chemists are very practical and work at room temperature. So the standard environment is in fact:

Temperature: 25^oC or 298K

Pressure: 1 atm

(Concentration: 1M) standard electrode potentials: ion concentration

So in the exam or any other chemistry situation, always use the above and not anything else.

So those standards are the only one that IB will use in their examinations, and not STP/RTP/SATP and whatnot?

And I suppose they will not specify the temperature and pressure if they are talking about standard. And expect you to know that it is 298K and 1atm.

Thanks!

[Keel]

Yes absolutely,

If you look at all the past paper answers when they ask for standard conditions, they only accept these values of temperature, pressure (and molarity). (It doesn't matter whether you put 25⁰C or 298K, both are accepted, but remember the units.) Anything else is not accepted.

[ervo]

Physicists are weird people and they like to work at 0^oC and use strange units such as pascals, whereas we chemists are very practical and work at room temperature. So the standard environment is in fact:

Temperature: 25^oC or 298K

Pressure: 1 atm

(Concentration: 1M) standard electrode potentials: ion concentration

So in the exam or any other chemistry situation, always use the above and not anything else.

So those standards are the only one that IB will use in their examinations, and not STP/RTP/SATP and whatnot?

And I suppose they will not specify the temperature and pressure if they are talking about standard. And expect you to know that it is 298K and 1atm.

Thanks!

Yes, it is 1atm, but just using 100kPa will probably cause you to lose marks, as it is not correct. I doubt you will ever have to write anything to 1sf, thus 101kPa or 101.3kPa is better. If you look in the Data Booklet, you will see that they give you the equation: 1 atm = 1.01 x 10⁵ Pa

I'd be wary of nflavour's advice - atm are not normally used in calculations, since the pascal is the SI unit of pressure.

Edited April 14, 2011 by ervo