Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid fuel rocket motors. The reaction is

:math> Fe 2 O 3 ( s ) + 2 Al ( s ) → 2 Fe ( l ) + Al 2 O 3 ( s )

l type='a'>

What mass of iron(III) oxide must be used to produce 25.69 g of iron?

What mass of aluminum must be used to produce 25.69 g of iron?

What is the maximum mass of aluminum oxide that could be produced along with 25.69 g of iron?

(a)

Interpretation:

The mass of iron(iii) oxide must be used to produce 25.69 g of iron should be calculated.

Concept Introduction:

It is important to recognize that the coefficients in a balanced equation give the relative number of molecules.

Because atoms are not changed or destroyed in a chemical reaction one must always balance a chemical reaction. That is, one must choose the coefficients that gives the same number of each type of atoms on both sides, using the smallest set of integers.

Number of moles of a substance is related to mass and molar mass as follows:

n=mM

Here, m is mass, M is molar mass.

The balanced chemical reaction is as follows:

Fe2O3(s) + 2Al(s)→2Fe(l)+Al2O3(s)

molar mass of Fe =55.85 g/molmolar mass of O  = 16.00 g/molmolar mass of Al =26.98 g/mol55.85 g = 1 mol Fe(l)25.69 g→?

The number of moles in given mass of Fe can be calculated as follows:

n= 1 mol Fe55.85 g× 25.69 g =0.45998 mol≈0.46 mol

According to balanced chemical reaction, 2 mol of Fe is obtained from 1 mol of Fe2O3(s) thu, the number of moles of Fe2O3(s) to produce 0

(b)

Interpretation:

The mass of aluminum that must be used to produce 25.69 g of iron should be calculated.

Concept Introduction:

It is important to recognize that the coefficients in a balanced equation give the relative number of molecules.

Because atoms are not changed or destroyed in a chemical reaction one must always balance a chemical reaction. That is, one must choose the coefficients that gives the same number of each type of atoms on both sides, using the smallest set of integers.

Number of moles of a substance is related to mass and molar mass as follows:

n=mM

Here, m is mass, M is molar mass.

(c)

Interpretation:

The mass of aluminum oxide is produced with 25.69 g of iron should be calculated.

Concept Introduction:

It is important to recognize that the coefficients in a balanced equation give the relative number of molecules.

Because atoms are not changed or destroyed in a chemical reaction one must always balance a chemical reaction. That is, one must choose the coefficients that gives the same number of each type of atoms on both sides, using the smallest set of integers.