Answer:
2 will be the number
Explanation:
To balance a chemical reaction like this one, we have to know the priority order of balance.
In general, the priority order for balancing is:
Metals > Non metals > Hydrogen > Oxygen
Following this order, we can balance almost any chemical reaction we have:
Now, using this priority, let's balance the equation.
The metals here are Fe and Na, so let's check both of them in both sides of the reaction.
In the case of Fe, we have the same number of atoms in reactants (1) and in the product, so, in theory, we do not need to balance this metal.
In the case of Na, we can see that in reactants we have 2 atoms, but in the products we have 1, so we need to put a number 2 next to the Na in the product. It will keep like this: 2NaCl. This 2, also alter the number of Cl, but we will see that later. We have the metals balanced.
Let's see the non metals which are Carbon and chloride. In the case of C, we have in both sides the same number of C (1). In the case of Chloride, we also have the same number on both sides (2), because we put a 2 in products to balance the Sodium, and this balance the chloride too. So non metals are balanced.
We do not have hydrogens, so, let's see the oxygen. We have 3 in reactants and 3 in products, so they are already balanced, so we do not need to balance.
The balanced equation will be:
FeCl₂ + Na₂CO₃ -----> FeCO₃ + 2NaCl
Therefore the coefficient of NaCl is 2.
