Answer
0.701 g de HCl
Work Step by Step
First, we calculate the molecular mass of $Al(OH)_3$.
Molecular mass of $Al(OH)_3$= (1x27)+(3x16)+(3x1) = 78 g/mol.
How many moles of $Al(OH)_3$ have in 0.500 g?
$\frac{0,500 g}{78g/mol}= 6,41\times10^{-6}$ mols de $Al(OH)_3$
This will react with $6,41\times10^{-6}\times3$ HCl = 0,0192 mol HCl.
Now, we will find the molar mass of HCl:
MM(HCl) = (1x1,008)+(1x35,45) = 36,5 g/mol
Finally, the mass of 0.0192 mols = 0,0192 mols x 36,5 g/mol = 0,701 g HCl.