Answer:
Mg (s) + 2HCl -----> H2(g) + MgCl2 (aq)
Explanation:
This reaction produces hydrogen gas and magnesium chloride. So, we have :
Mg (s) + HCl -----> H2 (g) + MgCl2 (aq)
In other to balance this reaction, we then add "2" to HCl on the left hand side of the equation so that the number of hydrogen and chlorine on both sides will be equal.
Thus our balanced equation would be:
Mg (s) + 2HCl (aq) -----> H2 (g) + MgCl2 (aq)