Finding pressure increase required to impart 1J of work

In summary, the conversation discusses estimating the pressure increase needed to impart 1 J of mechanical work to 1 mol of silver and alumina at room temperature. The equation for mechanical work is correctly stated as -PdV, and it is suggested to substitute numbers into it assuming a starting pressure of 1 atm. The same equation can be used for part (b), and unit conversions may be necessary if the molar volume is given in cc/mol. It is also mentioned that a separate thread should be started if further assistance is needed, and the Beta value for silver in the textbook is 9e7 atm^-1, and the molar volume is given as V^S= 10.27 cc/mol, with a separate
  • #1
geobot
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0

Homework Statement


a) Estimate the pressure increase required to impart 1 J of mechanical work in reversibly compressing 1 mol of silver at room temperature.
b) What pressure rise would be required to impart 1 J of work to 1 mol of alumina at room temperature? For AL2O3 take the molar volume to be 25.715 (cc mol^-1) and Beta= 8.0 x 10^-7 (atm)^-1

Homework Equations


mechanical work = -PdV
dV=V.alpha.dT - V.beta.dP
(maybe: dU = (Cp - PV.alpha)dT + V(P.beta - T.alpha)dP )

The Attempt at a Solution


I have tried and tried to come up with a solution but I just can't figure it out.
See attached jpg.
I would appreciate any thoughts on the question
 

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  • #2
Your equation in the snapshot involving P's is correct. Just substitute numbers into it. Assume that the starting pressure is 1 atm.

Chet
 
  • #3
Chestermiller said:
Your equation in the snapshot involving P's is correct. Just substitute numbers into it. Assume that the starting pressure is 1 atm.

Chet

Thank you, can I use that equation for part (b) as well? It does not specify that it is mechanical work or reversible there.
 
  • #4
geobot said:
Thank you, can I use that equation for part (b) as well? It does not specify that it is mechanical work or reversible there.
Same as (a).
 
  • #5
Chestermiller said:
Same as (a).
Oh wow, I've been really over thinking this question it seems! thanks again!
 
  • #6
can I have a solution to this problem?
 
  • #7
Jairaj Joshi said:
can I have a solution to this problem?
Nope. That's contrary to Physics Forum rules (you should read the guidelines). If you wish to solve this problem and you can't glean enough hints from the current thread's content then you can show your own attempt and present what part you don't understand, or start a new, separate thread and show your attempt there.
 
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Likes Chestermiller
  • #8
Is there any unit conversions that need to be done if my molar volume is given in cc/mol I thought I might need to convert to m^3. The beta value for silver given in my textbook is 9e7 atm^-1, and the molar volume is given as V^S= 10.27 cc/mol, but there is also a V^L=11.54 cc/mol, and I'm not sure of the difference. I know this is an old thread, but any help would be greatly appreciated. I came to the same equation, but cannot get a correct answer.
 

1. What is the formula for calculating the pressure increase required to impart 1J of work?

The formula for calculating the pressure increase required to impart 1J of work is:
P = W/V
Where P is the pressure increase, W is the work done, and V is the volume over which the work is done.

2. How do I convert units when calculating the pressure increase required to impart 1J of work?

To convert units when calculating the pressure increase, you can use the following conversions:
1 Joule = 1 Newton * meter
1 Pascal = 1 Newton / meter^2
Therefore, to convert from Joules to Pascals, you can divide the value by the volume over which the work is done.

3. Can the pressure increase required to impart 1J of work be negative?

Yes, the pressure increase required to impart 1J of work can be negative if the work is done in a way that decreases the volume. This may happen, for example, when a gas expands and does work on the surroundings.

4. How does the pressure increase required to impart 1J of work relate to the force applied?

The pressure increase required to impart 1J of work is directly proportional to the force applied. This means that as the force increases, the pressure increase required also increases. This relationship is described by the formula:
P = F/A
Where P is the pressure increase, F is the force applied, and A is the area over which the force is applied.

5. Is the pressure increase required to impart 1J of work the same for all substances?

No, the pressure increase required to impart 1J of work varies depending on the substance and the conditions under which the work is done. For example, a gas may require a different pressure increase compared to a solid or liquid. Additionally, factors such as temperature and pressure can also affect the pressure increase required to impart 1J of work.

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