If I add 25 grams of Fe(OH)2 to 25 ml of water, what is the percent by mass of Iron (II) hydroxide in this solution?

50%

Explanation:

Step 1: Calculate the mass of water

Since we don't know the actual temperature at which the solution is prepared, we will assume the density of water is about 1 g/mL.

Step 2: Calculate the mass of the solution

The mass of the solution is the sum of the mass of the solute (Iron (III) hydroxide) and the mass of the solvent (water).

Step 3: Calculate the percent by mass of Iron (III) hydroxide in the solution