Answer: The mass of aluminium hydroxide obtained is 14.196 grams.
Step-by-step explanation:
To calculate the number of moles, we use the equation:
.....(1)
Given mass of aluminium sulfide = 13.7 g
Molar mass of aluminium sulfide = 150.158 g/mol
Putting values in equation 1, we get:

The chemical reaction of aluminium sulfide with water follows the equation:

By Stoichiometry of the reaction:
1 mole of aluminium sulfide produces 2 moles of aluminium hydroxide.
So, 0.091 moles of aluminium sulfide will produce =
of aluminium hydroxide.
To calculate the mass of aluminium hydroxide, we use equation 1:
Moles of aluminium hydroxide = 0.0182 moles
Molar mass of aluminium hydroxide = 78 g/mol
Putting values in equation 1, we get:

Hence, the mass of aluminium hydroxide obtained is 14.196 grams.