Which problem is already balanced? NaOH+3AgNO_(3)- gt 3AgOH+NaNO_(3) 2Na+2H_(2)O-gt 2NaOH+H_(2) PbO_(2)+2H_(2)-gt H_(2)SO_(4) SO_(2)+H_(2)Oarrow H_(2)SO_(4)

The balanced chemical equation is:<br /><br />$SO_{2}+H_{2}O\rightarrow H_{2}SO_{4}$<br /><br />In this equation, the number of atoms of each element is the same on both sides of the equation, which means it is balanced.