Question

Question #171b9

Answer 1

About `26` `mL` of the magnesium solution.

Explanation:

`2HCl(aq) + Mg(OH)_2(s) rarr MgCl_2(aq) + 2H_2O(l)`

The equation above is balanced, and gives a stoichiometric picture of the reactivity. Two equiv hydrochloric acid are required to neutralize the magnesium salt.

If `35.75` `mL`, `0.175` `mol*L^-1` hydrochloric acid were used, then this represents a molar quantity of `35.75xx10^(-3)cancelLxx0.175` `mol*cancelL^-1` `=` `6.26xx10^(-3) mol` `HCl`.

By the stoichiometry of the reaction, there were thus `3.23xx10^(-3) mol` `Mg(OH)_2`.

We had `0.125` `mol*L^-1` magnesium hydroxide solution available; thus `(3.23xx10^-3 cancel(mol))/(0.125*cancel(mol)*L^-1)` gives an answer in litres (why?).