Step 1 :Given that the density of iron is \(7.874 \, \text{g/cm}^{3}\), and the dimensions of the rectangular block of iron are \(3.000 \, \text{cm} \times 4.000 \, \text{cm} \times 5.000 \, \text{cm}\).
Step 2 :The volume of a rectangular block is calculated by multiplying its length, width, and height. So, \(\text{Volume} = 3.000 \, \text{cm} \times 4.000 \, \text{cm} \times 5.000 \, \text{cm} = 60.0 \, \text{cm}^{3}\).
Step 3 :The mass of a rectangular block can be calculated by multiplying its volume by its density. So, \(\text{Mass} = \text{Volume} \times \text{Density} = 60.0 \, \text{cm}^{3} \times 7.874 \, \text{g/cm}^{3} = 472.44 \, \text{g}\).
Step 4 :Final Answer: The mass of the rectangular block of iron is \(\boxed{472.44}\) grams.