The reactants are the substances on the left side, which react and give the products on the right side.
The reactants are Fe and O.
The product is Fe2O3.
The arrow to the right means that the reaction is going in only one direction — the only reaction happening at the moment is that Fe and O are making Fe2O3.
(s) means the substance is in the solid state, and (g) means in a gaseous state (or the substance is a gas in that reaction).
A. phase changing. Physical change is any change in matter that involves the substance going from one physical state to another, and phase change is most commonly used to describe transitions between solid, liquid and gaseous states of matter.
Answer:

Explanation:
We are given the percent composition: 22.5% phosphorus and 77.5% chlorine.
We can assume there are 100 grams of this compound. We choose 100 because we can simply use the percentages as the masses.
Next, convert these masses to moles, using the molar masses found on the Periodic Table.
- P: 30.974 g/mol
- Cl: 35.45 g/mol
Use the molar masses as ratios and multiply by the number of grams. 

Divide both of the moles by the smallest number of moles to find the mole ratio.


The mole ratio is about 1 P: 3 Cl, so the empirical formula is written as:<u> PCl₃</u>
If the gases are at the same temperature and pressure, the ratio of their effusion rates is directly proportional to the ratio of the square roots of their molar masses:
<h3>Graham's law of diffusion </h3>
This states that the rate of diffusion of a gas is inversely proportional to the square root of the molar mass i.e
R ∝ 1/ √M
R₁/R₂ = √(M₂/M₁)
Where
- R₁ and R₂ are the rates of the two gas
- M₁ and M₂ are the molar masses of the two gas
From the Graham's law equation, we can see that the ratio of the rates of effusion of the two gases is directly proportional to the square root of their molar masses
Learn more about Graham's law of diffusion:
brainly.com/question/14004529
#SPJ1