Question

Magnesium is added to a solution to check for acidity. If the solution is an acid, what will happen?

Answer 1

Hydronium ion, `H_3O^+` or `H^+`, will oxidize magnesium metal to give dihydrogen.

Explanation:

`Mg(s) + 2H_3O^(+) rarr Mg^(2+) + H_2(g)uarr +2H_2O(l)`

Answer 2

The acid and magnesium will together form a salt and `H_2(g)`.

Explanation:

Magnesium is an active metal, which means that a salt and `H_2` gas will be formed as a result of a chemical reaction with any acid. For example, if there is `HCl` (hydrochloric acid) in the solution, they will together form `MgCl_2` and `H_2`.
Some other examples of chemical equations which include `Mg` and an acid:

`2Mg + H_2SO_4 -> Mg_2SO_4 + H_2`
`Mg + 2HNO_3 -> Mg(NO_3)_2 + H_2`
`Mg + 2 H_3PO_4 = Mg(PO_4)_2 + 3 H_2`