Answer
102.6 g/mol.
Work Step by Step
1. Write the equation of the titration to know the proportions.
*All Alkali Metals (X) have +1 as charge of their Ions.
$X^{+}(O^{}H^{})^{-}$ + $H^{+}Cl^{-}$
1 $X^{+}(O^{}H^{})^{-}$ + 1 $H^{+}Cl^{-}$
2. Find the amount of mols (HCl) needed for the titration:
molarity = nº of moles (solute) $\div$ volume (solution)(L)
2.5 = nº of moles $\div$ 0.017
nº of moles = 2.5 * 0.017
nº of moles = 0.0425
3. Because the proportion is 1 to 1, now we know that we had 0.0425 moles of the alkali metal hydroxide.
4. With the number of moles and the mass, let's calculate the molar mass of the hydroxide.
molar mass = mass(g) $\div$ nº of moles
molar mass = 4.36 $\div$ 0.0425
molar mass = 102.6
