This is an acid-base reaction (neutralization): Mg(OH)2 is a base, H2SO4 is an acid.
Reactants:


, Sulfuric acid, concentrated (> 51% and < 100%)
, H2SO4
, Battery acid
, Hydrogen sulfate
, [SO2(OH)2] 
; Colorless to dark-brown, oily, odorless liquid. [Note: Pure compound is a solid below 51°F. Often used in an aqueous solution.] 
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