Answer:
2.7 mL
Explanation:
The equation of the reaction is;
2AlBr3 + 3Cl2 -----> 2AlCl3 + 3Br2
Number of moles in 2.12 x 1022 formula units of aluminum bromide
1 mole of AlBr3 = 6.02 * 10^23 formula units
x moles = 2.12 x 1022 formula units
x = 2.12 x 1022 formula units  * 1 mole/ 6.02 * 10^23 formula units
x = 0.0352 moles of AlBr3
According to the reaction equation;
2 moles of AlBr3 produces 3 moles of Br2
0.0352 moles of AlBr3 produces 0.0352 moles  *  3 moles /2 moles
= 0.0528 moles of Br2
Mass of Br2 produced = 0.0528 moles of Br2 * 159.808 g/mol
Mass of Br2 produced = 8.44g
But density = mass/volume
volume = mass/density
volume of Br2 = 8.44 g/ 3.12 g/mL
volume of Br2 = Â 2.7 mL