Over the years, the thermjte reaction has been used for welding railroads, in incendiary bombs, and to ignite solid fuel rocket monitors. The reaction is Fe2O3(s) + Al(s) ---> 2Fe(l) + AI2O3(s). What mass of iron (iii) oxide(rust) must be used to produce 15.0g of molten iron.

Fe2O3(s) + 2Al(s) ---> 2Fe(l) + AL2O3(s).

Here are the steps to work any regular stoichiometry problem.

1. Write and balance the equation. You have that.
2. Convert 15.0 g Fe to mols. mol = grams/atomic mass Fe.
3. Using the coefficients in the balanced equation, convert mols Fe to mols Fe2O3. 2 mol Fe requires 1 mol Fe2O3.
4. Now convert mols Fe2O3 to grams. g = mols x molar mass.

To calculate the mass of iron (III) oxide (rust) required to produce 15.0g of molten iron using the thermite reaction, we need to use stoichiometry.

Stoichiometry involves using balanced chemical equations to relate the number of moles or masses of substances involved in a chemical reaction. In this case, we have the balanced equation:

Fe2O3(s) + Al(s) ---> 2Fe(l) + Al2O3(s)

First, we need to determine the molar mass of Fe2O3. From the periodic table, we find that the molar mass of iron (Fe) is approximately 55.85 g/mol, and the molar mass of oxygen (O) is about 16.00 g/mol. Since there are two iron atoms and three oxygen atoms in Fe2O3, we can calculate its molar mass as follows:

Fe2O3:
(2 x 55.85 g/mol) + (3 x 16.00 g/mol) = 159.70 g/mol

Next, we can set up a proportion using the molar masses and the balanced equation:

(159.70 g Fe2O3 / 2 mol Fe) = (15.0 g Fe2O3 / x mol Fe)

Cross-multiplying and solving for x, we can find the number of moles of Fe2O3 required to produce 15.0g of molten iron:

x mol Fe = (15.0 g Fe2O3) x (2 mol Fe / 159.70 g Fe2O3) ≈ 0.187 mol Fe

Finally, we'll convert the moles of Fe2O3 to mass:

Mass of Fe2O3 = (0.187 mol) x (159.70 g/mol) ≈ 29.83 g

Therefore, approximately 29.83 grams of iron (III) oxide (rust) must be used to produce 15.0g of molten iron using the given thermite reaction.