Phosphorus tribromide decomposes to form phosphorus and bromine, like this: 4PBr3(g)-->P4(g)+6Br2(g)
Also, a chemist finds that a certain temperature at the equilibrium mixture of phosphorus tribromide, phosphorus, and bromine has the following composition:
Compound pressure at equiibrium
PBr3 97.4 atm
P4 99.2 atm
Br2 97.2 atm
Calculate the value of the equilibrium constant Kp for this reaction.

Kp = 929551.4

Explanation:

First of all, we state the equilibrium:

4PBr₃ (g) ⇄ P₄(g) + 6Br₂(g)

In order to determine Kp, we need the partial pressure of each gas at equilibrium. Expression for Kp is:

{(Parial Pressure P₄) . (Partial Pressure Br₂)⁶} / (Partial Pressure PBr₃)⁴

Kp = 99.2 . 97.2⁶ / 97.4⁴

Kp = 929551.4

Take account that Kp can be also calculated from Kc.

Kp = Kc (RT)^Δn where Δn is the value for (final moles - initial moles) of any gas

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.