5.2 moles of nitrogen gas are contained in a 3.4 L container. If pressure is kept constant what is the final molar amount of gas present in the container if gas is added until the
volume has decreased to 2000 mL?

The answer to your question is 3 moles of AlCl₃

Explanation:

Process

1.- Write and balance the equation

                  Al(NO₃)₃ + 3NaCl   ⇒   3NaNO₃  +  AlCl₃

2.- Determine the limiting reactant

Theoretical proportion     1 mol Al(NO₃)₃ :  3 moles of NaCl                  

Experimental proportion   4 moles Al(NO₃)₃ : 9 moles NaCl

From these values, we determine that the limiting reactant is NaCl because the number of moles increases three times and the number of moles of Al(NO₃)₃  increases four times.

3.- Determine the amount of AlCl₃ using proportions

                       3 moles of NaCl 1 mol of AlCl₃

                       9 moles of NaCl  x

                       x = (9 x 1) / 3

                       x = 9 /3

                       x = 3 moles