Reducing the volume of the container increases pressure. This results in a higher frequency of gas particle collisions, thereby increasing the rate of the reaction.

Since decreasing the volume of the container has the effect of increasing pressure, equilibrium is shifted to the right. An increase in pressure has the result of favoring the side of the reaction with fewer moles of gas. (According to the balanced equation, there are 4 moles on the reactant side as opposed to 2 moles on the product side).

By adding NaF to the equation, 1M of F^- ions are added to the solution. Thinking in terms of Le Chatlier's principle, the addition of a compound on one side of the equation will cause a shift to the other side of the reaction.

It DOES NOT affect the solubility product constant. Since there is an addition to the products side of the reaction, there will be a shift to the left, and more salt (reactant) will be precipitated. As a result, the solubility of the salt has decreased, because of the addition of NaF. This is known as the common ion effect.

You need to understand Le Chatelier’s principle to solve this question. Le Chatelier’s principle states that the addition of excess molecules to one side of a reaction will shift the equilibrium toward the other side. This shift makes sure that the reaction remains at equilibrium.

If you add hydrogen gas, reaction 1 will shift to the right and will produce more ammonia. Since more ammonia is produced, reaction 2 will shift to the right to produce more ammonium ions and hydroxide ions. Statement I is correct.

Adding  to the solution will increase the concentration of hydroxide ions. This means that the equilibrium of reaction 2 will shift to the left, away from hydroxide ions. While the overall hydroxide ion concentration may increase due to the addition of the base, the equilibrium for the reaction will shift away from the hydroxide ions, making statement II incorrect.

Finally, adding  will generate  ions. These  ions will react with the  ions and form water, which will decrease the overall concentration of hydroxide ions. The equilibrium of reaction 2 will shift to the right to produce more ammonium and hydroxide ions. Statement III is correct.

Increasing the pH is equivalent to decreasing hydrogen ion concentration or increasing hydroxide ion concentration. This increase in hydroxide ion concentration will shift the equilibrium of reaction 2 to the left, producing more ammonia. This is a fundamental point of Le Chatelier's principle.

This phenomenon is called the common-ion effect. When a compound dissolves in water it dissociates into ions. Increasing the concentration of one of these ions will shift the equilibrium towards the compound, thereby making it hard for the compound to dissolve in water (decreases solubility of compound). The ionic compound may have been something like silver chloride, which has a low solubility in water. A small amount may dissolve in aqueous solution, but the preexistence of chloride ions in the solvent would reduce the already low solubility and generate a precipitate.

Increasing chloride ion concentration shifts equilibrium to the left. While this phenomenon is directly linked to Le Chatelier's principle, the direct term is the common-ion effect.

A dissociation reaction does occur, but that does not explain the formation of the precipitate in only one solution. Also, since equal amounts of the ionic compounds are added to each solvent, we cannot make any conclusions about saturation.

When thinking about the solubility of a salt, it helps to use Le Chatelier's principle. The solubility of a salt is dependent on the amount of ions that are created by the precipitate in solution. As a result, we decrease the solubility by increasing the amount of ions from the salt in solution.

In this case, increasing the amount of calcium or carbonate ions will shift the reaction to the left, decreasing solubility.

The common-ion effect tells us that when an ion made by the salt is increased by another substance, the solubility of the salt will decrease. Calcium chloride will dissolve completely in solution, and will increase the amount of calcium ions. This will shift the reaction to the left, thus reducing the solubility of the precipitate.

According to Le Chatelier's principle, when a system at equilibrium is disturbed, the system will react to restore equilibrium. In other words, it will seek to undo the stress. Here, if hydrogen gas is removed, the reaction will shift toward the reactants to re-form it. In the process, more nitrogen will be produced.

This is a Le Chatlier shift problem. When the equilibrium of a chemical reaction is disturbed, the reaction shifts to the side to minimize the change. Here, increasing H₂CO₃ would shift the reaction to the right to minimize the addition of the acid. Shifting the reaction to the right would thus increase the concentration of HCO₃^-.

Remember that Le Chatlier’s principle says that pure liquids and solids do not change the equilibrium of the reaction. Regardless of where in the reaction the pure liquid or solid is present, no equilibrium shift would occur.