Ideal Gas Equation: Calculating R in PV=nRT

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Discussion Overview

The discussion revolves around the ideal gas equation, PV=nRT, specifically focusing on determining the appropriate value of the gas constant R when using specific units for pressure, volume, amount of substance, and temperature. The context is primarily homework-related, with participants exploring the implications of unit conversions in the equation.

Discussion Character

  • Homework-related, Exploratory, Technical explanation

Main Points Raised

  • One participant expresses confusion about how to approach the problem, indicating a lack of understanding of the ideal gas equation and its components.
  • Another participant suggests solving for R by replacing the variables with their respective units, although this response is somewhat vague.
  • A participant notes that the value of the gas constant is dependent on the units used, mentioning that R is typically expressed in joules per (kelvin x mol) and discusses the relationship between pressure in pascals and bar.
  • There is a suggestion to start with a known value of R (0.0821 L·atm/(mol·K)) and convert the pressure and volume to the appropriate units.
  • Some participants clarify that R does have units and provide a link to a resource for further information on the gas constant.
  • One participant questions whether the original problem statement might have been incorrect due to the lack of specified units, while another participant confirms the units provided in the question.

Areas of Agreement / Disagreement

Participants do not reach a consensus on how to proceed with the problem, as there is confusion regarding the units and the application of the ideal gas equation. Multiple viewpoints exist regarding the interpretation of the problem and the necessary steps to find R.

Contextual Notes

The discussion highlights limitations in the clarity of the original problem statement, particularly regarding the specification of units. There is also uncertainty about how to correctly apply unit conversions in the context of the ideal gas equation.

Dodabby
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Homework Statement



The ideal gas equation, PV=nRT, may have the following units:
P is given in bar (bar)
V is given in m3 (cubic meters)
N is given in mol (moles)
T is given in K (kelvin)

Which value of R would you use for the calculation if you were using the above units for the other variables in the calculation?

Homework Equations



Dont have any.

The Attempt at a Solution



I have no attempt at the solution as i honestly do not understand how to come to a conclusion. I am a first year university student, having just started a degree in Biochemistry - and i have three basic chemistry modules to complete before i can get onto Biochemistry.

This being a career change for me at age 34, and not having done science in school, i am really stuck and have been battling on this question for a week now.

Any help would be greatly appreciated - just an explanation of where to start would be of great help.

Thanks!
 
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Solve for R - and replace given symbols (P, V, n, T) with units.

--
methods
 
The gas constant's value is determined by its units. If you alter the units you need to alter the value of the constant also. The gas constant is joules per (kelvin x mol). If you multiply pressure in pascals by volume in metres you get joules. Since your volume is in metres already, you need to find out the relationship between pascals and bar.
At least, I think that's correct...
 
Borek said:
Solve for R - and replace given symbols (P, V, n, T) with units.
You beat me Borek!
Is what I said reliable?
 
Thank you for the response :)

Problem is - the question is exactly as i typed it. There are no units given, at all. Hence why i am stumped :/

Have they perhaps made a mistake, or am i really being clueless?
 
Dodabby said:
P is given in bar (bar)
V is given in m3 (cubic meters)
N is given in mol (moles)
T is given in K (kelvin)

No units?

--
methods
 
You could start with [tex]R = 0.0821 \frac{L\cdot atm}{mol\cdot K}[/tex] and convert the pressure and volume to the other units.
 

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