During the isothermal expansion, a confined ideal gas does (-150) J of work against its surroundings. This means that

Step-by-step solution

The First Law of Thermodynamics is expressed as U = Q - W , where U is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. Given that the system performs work against its surroundings of magnitude 150 J , W = 150 J . Since the process is isothermal and involves an ideal gas, the internal energy remains constant, so U = 0 . Substituting into the first law: 0 = Q - 150 J , which yields Q = 150 J . Thus, the heat added is 150 J , and the correct choice is A .