Physical Chemistry Question (work done during decomposition)

In summary: Your Name]In summary, the problem involves calculating the work done during the decomposition of 1 mole of CaCO3 at 800°C in a container with a piston, initially resting on the solid. The work done is equal to the external pressure (1 atm) multiplied by the change in volume (determined by the ideal gas law). The work done would be different if the container was open to the atmosphere, as there would be no external pressure acting on the system.
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Homework Statement



A sample consisting of 1.0 mol of calcium carbonate CaCO3(s) was heated to
800°C, when it decomposed (CaCO3 → CaO + CO2). The heating was carried out in a
container fitted with a piston which was initially resting on the solid. Calculate the work
done during complete decomposition at 1.0 atm. What work would be done if instead of
having a piston the container was open to the atmosphere?

Homework Equations



Expansion work against constant external pressure:

w=-pex[tex]\Delta[/tex]V

The Attempt at a Solution


Ok the textbook gives an example, so I tried following that. Because Vf>>Vi, and Vf=nRT/pex, then w=-pex x nRT/pex=-nRT (im assuming n is number of moles of CO2?). 1 mole of CaCO3 makes 1 mole of CO2, so plugging in numbers, I get 8.9kJ, although I don't use the 1 atm pressure at all, so I'm thinking I'm doing the second part of the question first. Any help would be appreciated.
 
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Thank you for your post. It seems like you are on the right track with your attempt at a solution. However, there are a few things that can be clarified to help you better understand the problem.

Firstly, when calculating the work done during the decomposition of CaCO3, you should consider the entire system, not just the CO2 produced. This means that you should consider the work done by the piston on the surroundings, as well as the work done by the surroundings on the piston.

Secondly, the pressure used in the equation for expansion work is the external pressure, which in this case is 1 atm. This is because the piston is initially resting on the solid, so the external pressure is equal to the atmospheric pressure.

Lastly, for the second part of the question, you are correct in assuming that the work done would be different if the container was open to the atmosphere. In this case, there is no external pressure acting on the system, so the work done would be equal to zero.

I hope this helps clarify the problem for you. Let me know if you have any further questions. Keep up the good work!
 

1. What is "work" in the context of physical chemistry?

In physical chemistry, "work" refers to the energy transfer that occurs when a system is subjected to a force and undergoes a displacement in the direction of that force.

2. How is work calculated during a chemical reaction or decomposition?

Work can be calculated during a chemical reaction or decomposition by determining the change in energy of the system (in the form of heat or work) and using the formula W = -ΔE, where W is work and ΔE is the change in energy.

3. Is work done during decomposition always negative?

In a closed system, work done during decomposition is usually negative because the system is losing energy, resulting in a decrease in work. However, in an open system, work can be either positive or negative depending on the direction of energy transfer.

4. How does the work done during decomposition affect the temperature of the system?

The work done during decomposition can affect the temperature of the system by either increasing or decreasing it. If the work done is positive (system gains energy), the temperature will increase. If the work done is negative (system loses energy), the temperature will decrease.

5. Can work be converted into heat during decomposition?

Yes, work can be converted into heat during decomposition. This is known as the first law of thermodynamics, which states that energy cannot be created or destroyed, but can be converted from one form to another.

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