Answer;
The molar mass of metal hydroxide = 121.66 g/ mole
The formula is Sr(OH)2
Explanation;
M(OH)2 + 2 HCl = MCl2 + 2 H2O
Moles of the acid = 2.5 x 56.9 / 1000 = 0.14225
Therefore; moles of hydroxide at the eq point = 0.0711 moles
These have a mass of 8.65g
Thus; mass of 1 mole = 8.65 / 0.0711
= 121.66 g / mole
That means the compound is Sr (OH)2 ..