The balanced chemical reaction is:
N2 +3 I2 = 2NI3
We are given the amount of product formed. This will be the starting point of our calculations.
3.58 g NI3 ( 1 mol NI3 / 394.71 g NI3 ) ( 3 mol I2 / 2 mol NI3 ) = 0.014 mol I2.
Thus, 0.014 mol of I2 is needed to form the given amount of NI3.
