Calculate the pressure-volume work for the given reaction

  • #1
anjauk2003
2
0
New user has been reminded to always show their work on schoolwork problems.
Homework Statement
Assume that 2.00 moles of water are formed according to the following reaction at constant
pressure (101.3 kPa) and constant temperature (298 K):
I have to calculate the pressure-volume work for the given reaction and i really dont know how to start or what to use. Can someone help me?
Relevant Equations
2 H2(g) + O2(g) --> 2 H2O(l)
I dont have an solution Attempt. Maybe something with PV=nRT but this is for ideal gas and H2O is liquid. An other formula they introduced us to is: dE=-P*V
 
Last edited:
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  • #2
anjauk2003 said:
dE=-P*V

If it is about work more like P*dV.

What is the initial volume of the mixture, and what is the final volume?
 
  • #3
Borek said:
If it is about work more like P*dV.

What is the initial volume of the mixture, and what is the final volume?
That's the problem. I dont have more information. I wrote down everything i got.
 
  • #4
You have everything you need. What is volume of water produced? What reacted?
 

FAQ: Calculate the pressure-volume work for the given reaction

What is pressure-volume work in the context of a chemical reaction?

Pressure-volume work refers to the work done by or on a system during a chemical reaction when there is a change in volume under constant pressure. It is an important concept in thermodynamics and is calculated using the formula W = -PΔV, where W is the work, P is the constant pressure, and ΔV is the change in volume.

How do you calculate the change in volume (ΔV) for a reaction?

The change in volume (ΔV) can be calculated by subtracting the initial volume (V_initial) from the final volume (V_final) of the system. Mathematically, ΔV = V_final - V_initial. In the context of gases, this can often be determined using the ideal gas law if the number of moles of gas changes during the reaction.

What units should be used for pressure and volume in the calculation?

Pressure is typically measured in atmospheres (atm) or pascals (Pa), and volume is measured in liters (L) or cubic meters (m³). It is important to ensure that the units are consistent when performing the calculation. For example, if pressure is in atm and volume is in liters, the work will be in liter-atmospheres (L·atm). To convert to joules (J), you can use the conversion factor 1 L·atm = 101.325 J.

How does the sign of the pressure-volume work indicate the direction of work done?

The sign of the pressure-volume work indicates whether the work is done by the system or on the system. If W is negative, it means the system is doing work on the surroundings (expansion). If W is positive, it means work is being done on the system by the surroundings (compression).

Can you provide an example of calculating pressure-volume work for a reaction?

Sure! Consider a reaction where 1 mole of gas expands from 2.0 L to 5.0 L at a constant pressure of 1 atm. The change in volume (ΔV) is 5.0 L - 2.0 L = 3.0 L. Using the formula W = -PΔV, we get W = -(1 atm)(3.0 L) = -3.0 L·atm. To convert this to joules, we use the conversion factor: -3.0 L·atm × 101.325 J/L·atm = -303.975 J. So, the pressure-volume work done by the system is -303.975 J.

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