Question

Iron (III) oxide can be reduced with CO to form metallic iron as described by unbalanced chemical equation,
$F{{e}_{2}}{{O}_{3}}+CO\to Fe+C{{O}_{2}}$
The number of moles of CO required to form one mole of Fe from its oxide is:
A) 1
B) 1.5
C) 2
D) 3

Answer 1

Hint: The equation regarding a chemical reaction taking place, should always be written in a balanced form.
- The number of atoms in the reactant side and in the product side should be the same.

Complete Solution :
So in the question we are asked how many moles of CO are required to form metallic iron as per the reaction equation given, but the given chemical equation is an unbalanced one.
- For solving this equation, we should know how to balance a chemical equation because we will calculate the number of moles of CO required from the balance equation.
- The method of balancing a chemical equations refers to multiply a number with the coefficient related to an atom or molecule so that the number of atoms in the reactant side i.e. the left side of the reaction arrow and the product side i.e. the right side of the reaction arrow remains the same.
So now let’s balance the equation.
$F{{e}_{2}}{{O}_{3}}+CO\to Fe+C{{O}_{2}}$
- In the product side there are two Fe atoms but there is only one Fe atom.
- There are four O atoms in the reactant side and only two O atoms in the product side.
- If we talk about the number of carbon atoms, there is only one carbon atom in the reactant and product side.
- So, now use a trial and error approach to balance the equation.
- Trial and error method means we will give the possible digits that will provide us with an equal number of atoms in the reactant and product side.
So the balanced chemical equation is,
$2F{{e}_{2}}{{O}_{3}}+6CO\to 4Fe+6C{{O}_{2}}$
So the number of atoms is equal in both the reactant and product in the above reaction.
We know that CO is the reducing agent used here and CO is reducing $F{{e}_{2}}{{O}_{3}}$ into Fe.
From the equation, we can conclude that 6 moles of CO is required to convert 2 moles of $F{{e}_{2}}{{O}_{3}}$ to 4 moles of Fe.
Now, we have to know how many moles of CO is required for one mole of Fe.
For one mole of Fe = $\dfrac{6}{4}$ = 1.5 moles of CO is required.
So, the correct answer is “Option B”.

Note: The subscripts present in each molecule should not be altered as if we change the subscripts it will change the stoichiometry of the chemical reaction and this fact should be taken care of.
- Balancing the chemical equation is an application of law of conservation of mass, in which it is said that the mass can neither be created nor destroyed in a chemical reaction, it is only conserved.