0.1125 moles
Total mass number of AlCl3 = 27 + (3x35.5) = 133.5
Number of moles equals mass divided by mass number
10:133.5=0.075 ( this is the number of moles of AlCl3)
To get the number of moles of Cl2, look at the coefficient of both AlCl3 and Cl2
0.075x3:2=0.1125 moles
I hope this helps