Suppose NaOH is added to the following system when it is at equilibrium.
NH3 (aq) + H2O (l) = NH4 (aq) + OH (aq)
a) in which direction will the reaction shift after the NaOH is added?
b) will this stress increase or decrease the value of the reaction quotient, Q?
a)The reaction will shift to the left in order to try and decrease the added OH.
b) Write the expression for Q and see if increased OH will caue Q to go up or go down.
a) Well, you know what they say about NaOH, it's a bit of a troublemaker! When NaOH is added to the system, it will increase the concentration of OH- ions. Since OH- is a product in the forward reaction, according to Le Chatelier's principle, the equilibrium will shift in the backward direction to help reduce the concentration of OH- ions.
b) As for the reaction quotient, Q, adding NaOH will increase the concentration of OH- ions, which will increase the numerator of Q. Since the concentrations of NH4+ and NH3 remain the same, the denominator of Q stays constant. Therefore, the stress from adding NaOH will increase the value of Q.
a) When NaOH is added to the system, it will increase the concentration of OH- ions in the solution. According to Le Chatelier's Principle, the system will shift in the direction that minimizes the stress caused by the change. In this case, since OH- is a product of the reaction, the reaction will shift towards the reactant side (NH3 and H2O) in order to consume the added OH- ions.
b) Adding NaOH to the system will increase the concentration of OH- ions, which will result in an increase in the products of the reaction (NH4+ and OH-) and a decrease in the reactants (NH3 and H2O). Therefore, the stress caused by adding NaOH will increase the value of the reaction quotient, Q.
To determine the direction in which the reaction will shift after NaOH is added and whether it will increase or decrease the value of the reaction quotient, Q, we need to analyze the changes in the concentrations of reactants and products.
a) When NaOH is added, it dissociates into Na+ and OH-. The OH- ions will react with the NH4+ ions in the existing equilibrium reaction to form more NH3 and H2O. This reaction can be represented as NH4+ (aq) + OH- (aq) = NH3 (aq) + H2O (l). Therefore, the reaction will shift towards the reactants (left) to consume the additional OH- ions added by NaOH.
b) The reaction quotient, Q, is calculated using the concentrations of reactants and products at a particular point in time. Since the addition of NaOH will increase the concentration of OH- ions, the overall concentration of the products NH4+ and OH- will increase, while the concentrations of the reactants NH3 and H2O will decrease. As a result, the value of Q will increase due to the increase in the products' concentrations and the decrease in the reactants' concentrations.