Answer:
The first step is to convert mL to L.
63.1 mL * (1 L / 1000 mL) = 0.0631 L
Next, we can use the formula:
moles = M * L
moles of AlCl3 = 4.20 M * 0.0631 L = 0.26502 moles
Finally, we can use the molar mass of AlCl3 to convert moles to grams:
0.26502 moles * 133.34 g/mol = 35.34 g
Rounded to the correct number of significant figures, the answer is:
35 g of AlCl3