Alloyed 5.7 g of aluminum with the required amount of sulfur. Determine the mass of aluminum sulfide.

Given:
m (Al) = 5.7 g

To find:
m (Al2S3) -?

Decision:
1) Write the equation of a chemical reaction:
2Al + 3S => Al2S3;
2) Calculate the molar masses of Al and Al2S3:
M (Al) = 27 g / mol;
M (Al2S3) = 150 g / mol;
3) Calculate the amount of substance Al:
n (Al) = m (Al) / M (Al) = 5.7 / 27 = 0.21 mol;
4) Determine the amount of substance Al2S3:
n (Al2S3) = n (Al) / 2 = 0.21 / 2 = 0.105 mol;
5) Calculate the mass of Al2S3:
m (Al2S3) = n (Al2S3) * M (Al2S3) = 0.105 * 150 = 15.75 g.

Answer: The mass of Al2S3 is 15.75 g.