Answer:
The balance equation is:
P₄(s) + 6Cl₂(g) → 4PCl₃(l)
Therefore the coefficient that should be placed in front of PCl₃ is 4
Step-by-step explanation:
The unbalanced reaction is:
P₄(s) + Cl₂(g) → PCl₃(l)
As we have 4 atoms of P, we need to add 4 in front of the PCl₃ but now we unbalance the chlorine.
In 4 moles of PCl₃ we have 12 Cl, so we must add 6 in the Cl₂ on the reactant side.
The balance equation will be:
P₄(s) + 6Cl₂(g) → 4PCl₃(l)