Question

Consider the following reaction:

iron (s) + chlorine (g) à iron (III) chloride
a. Write the balanced chemical equation.
b. 25.0 g of iron reacts with excess chlorine gas.
a. Calculate the moles of iron reactant.
b. Calculate the moles of iron (III) chloride.
c. Calculate the mass of iron (III) chloride.

Answer 1

Step-by-step explanation:

Fe + Cl₂ → FeCl₃

a. The balanced equation

All chemical equations obey the law of conservation of matter. To balance this above equation, we either inspect or use mathematical method to obtain a balanced equation.

We put coefficients a, b and c at the back of the compounds as shown below:

aFe + bCl₂ → cFeCl₃

For Fe:

a = c (i)

For Cl:

2b = 3c (ii)

let a = 1, c= 1

Solving for the unknown b, we have:

b =
`(3c)/(2)`

b =
`(3)/(2)`

The complete reaction equation is therefore:

Fe +
`(3)/(2)`Cl₂ → FeCl₃

or

2Fe + 3Cl₂ → 2FeCl₃

Problem a:

Mass of reacting iron = 25g

unknown: number of moles of iron

Solution

To find the number of moles, we apply the mole concept using the expression below:

`number of moles = (mass)/(molar mass) \\`

To find the molar mass of the reactant iron, we know atomic mass of iron is 56g.

The molar mass is therefore, 56gmol⁻¹

`number of moles = (25)/(56) \\`

number of moles of the iron reactant = 0.45mole

Problem b:

From the balanced equation of the reaction:

2Fe + 3Cl₂ → 2FeCl₃

2 moles of Fe produces 2 moles of FeCl₃

So 0.45mole of Fe would produce 0.45 mole of FeCl₃

Problem C:

Applying the mole concept;

mass of FeCl₃ = number of moles of FeCl₃ x molar mass of FeCl₃

number of moles of FeCl₃ = 0.45mole

molar mass of FeCl₃ = ?

Atomic mass of Fe = 56g

Cl = 35.5g

Molar mass of FeCl₃ = 56 + (3 x 35.5) = 56 + 106.5 = 162.5gmol⁻¹

mass of FeCl₃ = 0.45 x 162.5 = 73.1g