Question

Chlorine gas reacts with solid phosphorus to form phosphorus trichloride gas. Write a balanced chemical equation for this reaction.​

Answer 1

Explanation:

First write down the basic chemical equation with the reactants and products,

$\text{P}_4+\text{ Cl}_2\to\text{ PCl}_3$

Balancing the chemical equation*,

$\text{P}_4 (s) + 6 \text{Cl}_2 (g) \to 4 \text{PCl}_3 (l)$

$\color{blue}\text{Note: To balance any chemical equations, we should ensure the number of atoms of each elements are the same on both the product and reactant side.}$

$\color{blue}\text{The phosphorous molecule has 4 P, but the }\text{PCl}_3\text{ molecule on the product side only has one P atom. Therefore, we need 4 }\text{PCl}_3\text{ molecules to balance.}$

$\color{blue}\text{But that will mean we have }4\cdot 3=12\text{Cl atoms on the product side. So we need 6 }\text{Cl}_2 \text{ molecules on the reactant side.}$