# What is the relationship of pressure and temperature for gases?

### 7 Answers

- Anonymous2 months ago
Temperature goes up, pressure goes up.

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- Anonymous2 months ago
Friends with benefits, but one always ends up falling in love.

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- Dr WLv 72 months ago
If the gas is an ideal gas, we can say

.. "the pressure of a gas is directly proportional to the absolute

... temperature of the gas".

or

.. P/T = k.

If not ideal, we may have some complicated relationship like..

.. P = ((nR)/(V-nb)) * T - an² /V² .. which is of the form P = m*T + b

or

.. P = ρ RT + (BoRT - Ao - Co/T² + Do/T³ - Eo/T⁴ )ρ³ +(bRT - a

.. .. .. - d/T)ρ ³ + α(a + d/T)α⁶ + cp³ /T²(1 + γρ² ) exp(-γρ² )

which are clearly NOT directly proportional

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for the case of an ideal gas, we can write

.. P1V1 / (n1T1) = P2V2 / (n2T2)

and IF n and V are constant.. i.e.. n1=n2 and V1=V2, those terms drop

.. P1/T1 = P2/T2

This is known as "Amonton's law" and often ERRONEOUSLY named "Gay-Lussac's law"

************

Note the word erroneously... And by often I mean by a whole herd of misled chemists. It's like one chemist says

.. "hmm...

.. .. .. P1V1 = P2V2.... Boyle discovered that.. let's call it Boyles law

.. . .. .V1/T1 = V2/T2.. Charles discovered that.. let's call it Charles law

.. ..... V1/n1 = V2/n2.. Avogadro discovered that.let's call it Avogadro's law

... . .. P1V1/T1 = P2V2/T2.. that's all 3 combined.. "combined gas law"

.... hmm...

.. . ....P1/T1 = P2/T2.. what on Earth shall we call that?

.....hmm

.. .. ...the big names in the world of Chemistry and Physics that studied

.. ..... gases were Boyle, Charles, Avogadro and.. Gay Lussac who

.. . .. .basically worked on Charles' law. So let's name that last one after

.. . ....Gay-Lussac"... why not!

.. . soooo let's do this

.. . . ..P1/T1 = P2/T2... is now called Gay-Lussac's law. ('cause we say so)

then those misled chemists.. propagate that erroneous name to countless generations of more mislead chemists.

Folks, students, chemists, etc out there... the proper name for the relationship between P and T of an IDEAL GAS is "Amonton's law" named after Guillaume Amontons who discovered it 100 years before Gay-Lussac was born....

Want proof?

http://chemed.chem.purdue.edu/genchem/topicreview/...

https://chemdemos.uoregon.edu/demos/Amontons-Law#

https://chem.libretexts.org/Courses/Oregon_Institu...

https://opentextbc.ca/chemistry/chapter/9-2-relati...

https://www.mtsu.edu/chemistry/chem1010/pdfs/Chapt...

general chemistry textbooks

.. Zumdahl - Chemistry

.. Chang - Chemistry

.. Tro - Chemistry a molecular approach

.. Brown - Chemistry the central science

.. Petrucci - General chemistry Principles and applications

.. Silberberg - chemistry molecular nature of matter and change

ALL of those are used by high schools and Universities as AP and general chemistry textbooks. ALL of those cover Boyles law, Charles law, Avagodro's law, combined gas laws, ideal gas laws and other equations of state. NONE name P1/T1 = P2/T2 "Gay-Lussac's law". in fact, none even mention P1/T1 = P2/T2

*********

so.. anybody tells you

.. P1/T1 = P2/T2... then stands up and shouts out "GAY-LUSSAC'S LAW"

kindly correct them

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- Roger the MoleLv 72 months ago
Gay-Lussac's law (or Amontons' law) says pressure and temperature (in Kelvin) are directly proportional.

- Dr WLv 72 months agoReport
only for an ideal gas.. and it's not Gay-Lussac's(or Amonton's law). It's actually not named but should be called "Amonton's law" since he discovered the relationship 100 years before Gay-Lussac was born and since Gay-Lussac studied and applied "charles law".

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- JimLv 72 months ago
PV=nRT <<<memorize!!

n is moles, R is gas constant (use correct one!), T is temp in K (C+273.15)

Since you have a before and after with the same n &R simplifies to

PV/T initial = nR = PV/T final

Now sub in your numbers and solve

SI Units R values:

8.31446261815324 J⋅K−1⋅mol−1

8.31446261815324 m3⋅Pa⋅K−1⋅mol−1

8.31446261815324 kg⋅m2·K−1⋅mol−1s−2

8.31446261815324×103 L⋅Pa⋅K−1⋅mol−1

8.31446261815324×10−2 L⋅bar⋅K−1⋅mol−1

0.082057 L atm mol-1K-

US Customary Units R values:

0.730240507295273 atm⋅ft3⋅lbmol-1°R-1

10.731557089016 psi⋅ft3⋅lbmol-1°R-1

1.985875279009 BTU⋅lbmol-1°R-1

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