Final answer:
No, changing the concentration of reactants or products does not change the equilibrium constant (Keq) as the system will adjust to maintain the Keq value. Likewise, pressure changes only affect gases and have no effect on Keq. Only changes in temperature can alter the Keq value.
Step-by-step explanation:
Changing the concentration of reactants or products in a chemical reaction at equilibrium does not affect the value of the equilibrium constant (Keq). This is because the system will shift to reestablish the balance such that the ratio defined by the Keq expression remains constant. Changes in pressure also do not change the value of Keq, but it's crucial to note that only gases are affected by pressure changes. However, a change in temperature does affect the Keq value, causing it to either increase or decrease depending on whether the reaction absorbs or releases heat. For example, the decomposition of calcium carbonate (CaCO3 s) into calcium oxide (CaO s) and oxygen gas (O₂ g) is unaffected by the presence of solids or liquids, but the Keq would change if the temperature were altered.
In an equilibrium reaction such as the formation of hydrogen iodide (2HI g) from hydrogen (H₂ g) and iodine (I₂ g), if more product or reactant is added, the system shifts in a predictable manner to reestablish concentrations. This shift affects the reaction rates as described by the rate laws for the forward and reverse reactions, however, the Keq remains the same. A classic example of temperature affecting Keq is seen in the Haber-Bosch process, where an increase in temperature decreases the Keq value, while a decrease in temperature increases it.