Answer
b
Work Step by Step
We know that the number of moles of gas is cut in half by the reaction. After all, the volume of the container was cut in half, while the pressure and temperature did not change. Thus, we look for containers with three molecules in them, since the first container had six. This means that b is correct. Note, option a) cannot be correct since it involves the same molecules as before the reaction, meaning that no reaction would have taken place.
