Another high school chem question im stuck on??? PLEASE?

Question

i forget how to do this

in this equation Al2S3 + 6H2O --> 2Al(OH)3 + 3H2S

how many grams of aluminum hydroxide are obtained from 10.5 g of aluminum sulfide?

Answer 1

Moles Al2S3 = 10.5 g / 150.16 g/mol =0.0699

the rario between Al2S3 and Al(OH)3 is 1 : 2

moles Al(OH)3 = 2 x 0.0699 =0.140

Mass Al(OH)3 = 0.140 mol x 78 g/mol =10.9 g