Constant pressure
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Constant pressure
When they refer to constant pressure, are we referring to constant external pressure?
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Re: Constant pressure
Yes they are referring to constant external pressure, since a dynamic external pressure would do unnecessary work on a system, and thus be unreasonable problem to solve.
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Re: Constant pressure
Matt Sanruk 2H wrote:And this would be irreversible?
Yes this would be irreversible
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Re: Constant pressure
It would be irreversible and it would be referring to external pressure so w=0
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Re: Constant pressure
Yes, constant external pressure, as it allows the system to change somewhat independent of the external environment. For example, in the equation for an irreversible expansion work, W = - P external * delta V. However, if it is a gas in a container, pressure of the gas may be determined through the ideal gas law (but the system pressure will change).
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Re: Constant pressure
In a vacuum there is no external pressure, so there is nothing to push back against, meaning w=0
Re: Constant pressure
And so just because there is constant external pressure, the internal pressure can still be changing because of the reaction going on?
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Re: Constant pressure
Yes and I can give you some explanation on this.
You might refer to "constant pressure" mentioned when we try to calculate the amount of work done by a system. First, let's take a look at the definition of work: w = F(o)*D. F(o) here refers to an opposing force. Basically, this formula implies that you have to have an opposing force to do work, and the work you have done is how far you got by pushing against the opposing force. Hence, because w = -P*deltaV is a derived formula from w = F(o)*D, P also refers to external pressure.
Hope this can help! -_+
You might refer to "constant pressure" mentioned when we try to calculate the amount of work done by a system. First, let's take a look at the definition of work: w = F(o)*D. F(o) here refers to an opposing force. Basically, this formula implies that you have to have an opposing force to do work, and the work you have done is how far you got by pushing against the opposing force. Hence, because w = -P*deltaV is a derived formula from w = F(o)*D, P also refers to external pressure.
Hope this can help! -_+
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