For every 1 molecule of Magnesium hydroxide or Mg(OH)2 there will be 2 molecules of HCl neutralized.
If molar mass of magnesium hydroxide is 58.3197g/mol, the amount of mol in 5.50 g magnesium hydroxide should be: 5.50g/ (<span>58.3197g/mol)= 0.0943mol.
Then, the amount of HCl molecule neutralized would be: 2* </span>0.0943mol= 0.18861 mol
If molar mass of HCl is 36.46094 g/mol, the mass of the molecule would be: 0.18861 mol* 36.46094g/mol = 6.88grams
1 mL = 1 cm³
D = m / V
0.7857 = m / 17.16
m = 0.7857 x 17.16
m = 13.482 g