[填空题]
A given mass of magnesium was added to 500cm$^3$ of aqueous hydrochloric acid in a Styrofoam cup to form magnesium chloride. The temperature at the start was 18$^{\circ}C$ and and after the magnesium had dissolved, the temperature rose to 20$^{\circ}C$.
1.State a balanced chemical equation for this reaction.
2.Given that the change in enthalpy,ΔH is 0.185kJ and the specific heat capacity of water is 4.18J g$^{-1}$K$^{-1}$,calculate the mass of magnesium added to the hydrochloric acid.
m= g
3.Determine the systematic errors caused by the use of styrofoam cups.
