Here, the
analysis of mechanically reversible processes within closed systems
is presented acknowledging the infrequency of such processes. Indeed, their
practical application holds minimal interest. The value is found in the
simplicity afforded for computing alterations in state functions when a
specific change of state occurs.
In the context of a complex industrial process instigating a particular state change,the calculation of alterations in state functions is not executed for the path of the actual process. Instead, it is performed for a straight forward reversible process within a closed system that induces an equivalent statechange.
This feasibility arises due to the independence of changes in state functions from the process itself. The mechanically reversible process within a closed system proves beneficial and significant for this purpose, despite infrequent encounters with close approximations to such hypothetical processes impractical scenarios.
For 1 mole
of a homogeneous fluid housed in a closed system, the energy balance
can be formulated as:
dU = dQ +dW
The
representation of work for a mechanically reversible process within a closed
system is articulated as:
dW = −PdV.
Upon substitution
into the preceding equation, the resultant expression becomes:
dU = dQ −
PdV
This
stands as the general energy balance for one mole or a unit mass of
homogeneous fluid in a closed system undergoing a mechanically
reversible process.
In the
case of a constant-volume change of state, the sole conceivable
mechanical work is associated with stirring or mixing, an inclusion rejected
due to its inherent irreversibility. Consequently,
dU = dQ (const V)
Integration
leads to:
ΔU = Q (const V)
The
alteration in internal energy for a mechanically reversible,
constant-volume, closed-system process equals the quantity of heat
transferred into the system.
Comments