When given initial concentrations, we can determine the reaction quotient (Q) of the reaction. The reaction quotient is given by the same equation as the equilibrium constant (concentration of products divided by concentration of reactants), but its value will fluctuate as the system reacts, whereas the equilibrium constant is based on equilibrium concentrations.

By comparing the reaction quotient to the equilibrium constant, we can determine in which direction the reaction will proceed initially. 

The reaction quotient with the beginning concentrations is written below.

This shows that the ratio of products to reactants is less than the equilibrium constant. Since Q is less than K_eq in the beginning, we conclude that the reaction will proceed forward until Q is equal to K_eq. In this manner, the denominator (reactants) will decrease and the numerator (products) will increase, causing Q to become closer to K_eq.

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.

Scandium hydroxide dissociates according to this reaction.

As 0.1N HCl is added, it will quantitatively react with hydroxide anions to produce ScCl₃ and water.

Hydroxide will be removed from the above equilibrium, and the system will compensate by shifting the equilibrium to the right, according Le Chatelier's principle. As the equilibrium shifts to the right, more solid scandium hydroxide is hydrolyzed, resulting in increased solubility.

Since the system is originally at equilibrium and a stress is applied, Le Chatelier's principle is to be considered. By increasing the total pressure, the reaction will move in the direction toward which there are less molecules of gas.

Looking at the original reaction there are two moles of gas on the left and only one on the right, indicating that the reaction will shift to the right if the pressure is increased.

Us the solubility constant to calculate the answer to this question. We know that:

and

Since  is a very small number, we can assume that the concentration of chromate, , will be very small compared to the concentration of the added lead, 0.019 M. We can use the two known values ( and lead concentration) to solve for the unknown chromate concentration:

The activation energy is the minimum amount of energy required to start a chemical reaction. Based on the collision model, increasing the temperature, pressure, and concentration for a chemical reaction will decrease the activation energy. This is because increasing these factors increases the number of collisions of molecules, which is required for a reaction to occur. Therefore, decreasing the temperature would have the opposite effect causing the activation energy to increase, decreasing the likelihood of a reaction taking place.

According to Le Chatelier's principle, if an equilibrium reaction is disturbed by addition of a reactant or product, the equilibrium will shift to counteract the disturbance. Therefore, adding  to the system would cause the equilibrium to shift to the right, producing more  in order to reduce the concentration of .

The activation energy is the minimum amount of energy required to start a chemical reaction. Based on the collision model, increasing the temperature, pressure, and concentration for a chemical reaction will decrease the activation energy. This is because increasing these factors increases the number of collisions of molecules. Molecules must collide to react.