Well, you have lots to do, and not all of it is going to be clear. We're going to have to take this step by step.
If i put 4 mL of 5.4 M NaCl solution and then add 2 drops of 12M HCl solution to it, how would i balance that?
You can start by trying to write a chemical equation from the information that you've been given. Predicting products is never a simple task, and this reaction, in particular, is going to give us all some problems. Some context might help, in this case.
And how do i calculate the change in energy?
Well, a complete and balanced reaction will be needed, but its only the first step.
I hope you don't mind me answering your questions with more questions. That's what we do here. Its detailed in the
Forum Rules{click}. We'd like to see your attempt at this problem.