Calculate the mass of the salt formed by dissolving iron oxide (3) weighing 40 grams in an excess of nitric acid.

We compose the reaction equation and arrange the coefficients:
Fe2O3 + 6HNO3 = 2Fe (NO3) 3 + 3H2O.
Algorithm for solving the problem:
1) Calculation of the molar mass of iron oxide.
2) Calculation of the amount of iron oxide substance.
3) Determination of the amount of iron nitrate substance according to the reaction equation.
4) Calculation of the molar mass of iron nitrate.
5) Calculation of the mass of iron nitrate.
Decision:
1) 56 * 2 + 3 * 16 = 160.
2) 40/160 = 0.25 mol.
3) According to the reaction equation, there are two moles of iron nitrate per mole of oxide, then the amount of iron nitrate substance is: 0.25 / 2 = 0.125 mol.
4) 56 + 3 (14 + 48) = 242.
5) 0.125 * 242 = 30.25g – the answer.