The given expression is a chemical equation that represents a reaction between nitric acid (HNO3) and magnesium hydroxide (Mg(OH)2). The balanced chemical equation for the reaction is:
2HNO3 + Mg(OH)2 → 2H2O + Mg(NO3)2
In this reaction, two molecules of nitric acid react with one molecule of magnesium hydroxide to produce two molecules of water and one molecule of magnesium nitrate. The coefficients in the balanced chemical equation indicate that two moles of HNO3 react with one mole of Mg(OH)2 to produce two moles of H2O and one mole of Mg(NO3)2.