Relating AE to Heat and Work

The internal energy for Mg(s) and Cbtef) is greater than that of MgCl2(s). Sketch an energy diagram that represents the reaction MgCl2(s)--- Mg(s) + Cbte)- 

Suppose a system receives a deposit of work from the surroundings and loses a withdrawal of heat to the surroundings. Can we determine the sign of AE for this process  

We can use these ideas to write a useful algebraic expression of the first law of thermodynamics. When a system undergoes any chemical or physical change, the accompanying change in internal energy, AE, is the sum of the heat added to or liberated from the system, q, and the work done on or by the system, w  

The sign conventions for q, w, and AE are summarized in T TABLE 5.1. Notice that any energy entering the system as either heat or work carries a positive sign. 

For q + means system gains heat — means system loses heat 

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