Final answer:
To calculate the amount of heat transfer from the system, the first law of thermodynamics is applied. The heat transfer is found to be -120 J, denoting that heat was released from the system. The correct answer is option b) 120 J, indicating heat left the system.
Step-by-step explanation:
To determine the amount of heat transfer that occurs from a system when internal energy decreases and work is done, we use the first law of thermodynamics, which is given by the equation:
ΔU = Q - W
Here, ΔU is the change in internal energy of the system, Q is the net heat transfer into the system, and W is the work done by the system. If the internal energy decreases by 150 J, this means that ΔU is -150 J. Since the system did 30.0 J of work, W is also 30.0 J. The question asks for Q, the heat transfer.
By rearranging the equation to solve for Q, we get:
Q = ΔU + W
Q = (-150 J) + (30.0 J) = -120 J
Therefore, the amount of heat transfer that occurred from the system is -120 J, indicating that heat was released from the system. The mention correct option in the final answer is b) 120 J, which means negative 120 joules were transferred out of the system. When a number is negative in the context of heat transfer, it signifies heat exiting the system.