Question

What will be $\text{A+B+C}$ if the following reaction is balanced?

${\text{AFeCl}}_3\text{(aq)}+\text{BMgO}\text{(s)}\to {\text{Fe}}_2{\text{O}}_3\text{(s)}+{\text{CMgCl}}_2\text{(aq)}$

• A. 8
• B. 9
• C. 7
• D. 10

Answer 1

The correct option is A 8

To find the value of $\text{A, B, and C}$, we need to do the balancing of the given equation.

Number of $\text{Fe}$ atoms on the reactant side: 1
Number of $\text{Fe}$ atoms on the product side: 2

So we will multiply 2 on the left side to ${\text{FeCl}}_3$. Hence it will become;

$2{\text{FeCl}}_3\text{(aq)}+\text{MgO}\text{(s)}\to {\text{Fe}}_2{\text{O}}_3\text{(s)}+{\text{MgCl}}_2\text{(aq)}$

Number of $\text{Cl}$ atoms on the reactant side: $6(2\times 3)$;
Number of $\text{Cl}$ atoms on the product side: 2

So we will multiply 3 on the right side to ${\text{MgCl}}_2$. Hence it will become;

$2{\text{FeCl}}_3\text{(aq)}+\text{MgO}\text{(s)}\to {\text{Fe}}_2{\text{O}}_3\text{(s)}+3{\text{MgCl}}_2\text{(aq)}$

Now, the number of $\text{Mg}$ atoms are not balanced. In order to balance it, we will multiply 3 to $\text{MgO}$.

$2{\text{FeCl}}_3\text{(aq)}+3\text{MgO}\text{(s)}\to {\text{Fe}}_2{\text{O}}_3\text{(s)}+3{\text{MgCl}}_2\text{(aq)}$

Hence the equation is balanced and we also identified the value of $\text{A, B, and C}$, which are 2, 3, and 3 respectively.
So $\text{A+B+C}=8$.