Explain how the chemical equation: NaCl + BeF --> NaF + BeCl can be balanced.

First, I'll re-write the given equation that has to be
balanced.

NaCl + BeF2 --> NaF +
BeCl2

The first step is to create an element inventory.
We'll complete this inventory with the numbers of atoms of each element, from both sides
of equation.

We'll count how many atoms of Na are to the
left side and how many atoms of Na are to the right
side.

left: 1 atom

right 1
atom

We'll count how many atoms of Cl are to the left side
and how many atoms of Na are to the right side.

left: 1
atom

right 2 atoms

We'll count
how many atoms of Be are to the left side and how many atoms of Na are to the right
side.

left: 1 atom

right 1
atom

We'll count how many atoms of F are to the left side
and how many atoms of Na are to the right side.

left: 2
atoms

right 1 atom

Now, we'll
balance the equation by multiplying NaCl by 2 and NaF by
2.

2NaCl + BeF2 --> 2NaF +
BeCl2

Making the inventory we notice that the numbers of
atoms of each elements from both sides, are the
same.

Therefore, the balanced equation is:
2NaCl + BeF2 --> 2NaF + BeCl2.