The balanced equation is:
NH3 (g) + Cl2 (g) → N2 (g) + 2HCl (g)
Using the Ideal Gas Law, we can calculate the number of moles of nitrogen gas produced:
n = PV/RT = (1.20 atm)(16.0 L)/(0.0821 L·atm/mol·K)(296 K) = 0.786 mol
According to the balanced equation, 1 mole of nitrogen gas is produced for every mole of chlorine gas consumed. Therefore, we need 0.786 mol of chlorine gas.
To convert moles to grams, we need to use the molar mass of Cl2, which is 70.91 g/mol:
m = n × M = 0.786 mol × 70.91 g/mol = 55.8 g
Therefore, 55.8 grams of chlorine gas must react to produce 16.0 L of nitrogen gas at 1.20 atm and 23 °C.