Answer and Explanation:
For the following balanced reaction:
PCl₅(g) ↔ PCl₃(g) + Cl₂(g)
We can see that all reactants and products are gases, so it is an homogeneous equilibrium. The expression for the equilibrium constant Kp can be written from the partial pressures (P) of reactants and products as follows:

Where PPCl₃ is the partial pressure of PCl₃ (reactant), PCl₂ is the partial pressure of Cl₂ (reactant) and PPCl₅ is the partial pressure of PCl₅ (product).
Answer:
The first one and the last one.
Explanation:
Carbon dioxide is generated by cellular respiration and released into the atmosphere.
Photosynthesis makes oxygen that plants can release into the atmosphere.
Answer:
30 g of magnesium would be combined with 20 g of oxygen. The law used solving this problem is the Lavoisier Law of conservation of mass.
Explanation:
If 60 g of magnesium combines with 40 g of oxygen to make 100 g of magnesium oxide, then 30 g of magnesium will combine with 20 g of oxygen to make 50 g of magnesium oxide.
This happens because in a chemical reaction there is no creation or descruction of atoms, only a rearrangement. Therefore, the mass of reactants should be equal to the mass of products.
The following equation represents the proportions of the substances:
Mg + 1/2O₂ → MgO
They will most likely make a table, or some sort of graphing chart
Answer: Boiling because it makes the molecules in water bounce around.
Hope it helps.