What mass of aluminium hydroxide is needed to decompose in order to produce 65.0 L of water at STP in stoichiometry?

Aluminium Hydroxide on decomposition produces Al₂O₃ and Water vapors.

2 Al (OH) ₃ → Al₂O₃ + 3 H₂O

According to equation at STP,

67.2 L (3 moles) of H₂O is produced by = 78 g of Al (OH) ₃

So,

65.0 L of H₂O will be produced by = X g of Al (OH) ₃

Solving for X,

X = (65.0 L * 78 g) : 67.2 L

X = 75.44 g of Al (OH) ₂

Result:

75.44 g of Al (OH) ₂ is needed to decompose in order to produce 65.0 L of water at STP in stoichiometry