If 356 J of work is done by a system while it loses 289 J of heat,what is the value of
A)+645 J
B)-645 J
C)+67 J
D)-67 J
E)+134 J

Question

If 356 J of work is done by a system while it loses 289 J of heat,what is the value of 
A)+645 J 
B)-645 J 
C)+67 J 
D)-67 J 
E)+134 J

Quizplus · Accepted Answer

According to the First Law of Thermodynamics, the change in the internal energy of a system is equal to the heat added to the system minus the work done by the system: ΔU = Q - W. Rearranging this equation, we get: W = Q - ΔU.
In this case, the system does 356 J of work while it loses 289 J of heat. Therefore, W = 356 J and Q = -289 J (the negative sign indicates heat lost). We want to find the value of ΔU, which can be calculated as follows:
ΔU = Q - W = -289 J - 356 J = -645 J.
Since ΔU is negative, the internal energy of the system has decreased. Therefore, the best choice is B, which represents a negative value of 645 J.

If 356 J of Work Is Done by a System