AP Chemistry: Chapter 16 Quiz

Explanation
The conjugate acid of NH3 is NH4+. In a chemical reaction, NH3 can act as a base by accepting a proton (H+) to form NH4+. The addition of the proton converts NH3 into its conjugate acid, NH4+.

Explanation
The Ka value represents the acid dissociation constant, which indicates the strength of an acid. A lower Ka value indicates a weaker acid. Among the given options, HCN has the lowest Ka value of 4.9 x 10-10, making it the weakest acid.

Explanation
All of the given compounds, HNO2, (CH3)3NH+, HF, and CH3COOH, can act as Bronsted-Lowry acids because they are capable of donating a proton (H+) to another species. In the case of HNO2, it can donate a proton to form NO2-. (CH3)3NH+ can donate a proton to form (CH3)3N. HF can donate a proton to form F-. CH3COOH can donate a proton to form CH3COO-. Therefore, all of the above compounds can act as Bronsted-Lowry acids.

Explanation
NH3 is acting as a Lewis base because it donates a pair of electrons to form a coordinate bond with a metal ion or a Lewis acid. It is not acting as an Arrhenius base because it does not produce hydroxide ions (OH-) when dissolved in water.

Explanation
The conjugate base of OH- is O-2 because when OH- loses a proton (H+), it forms O-2. This is because OH- is a hydroxide ion, which is a strong base. In the process of losing a proton, it becomes negatively charged, resulting in O-2.

Explanation
The equilibrium that corresponds to the equilibrium constant Ka for HA is HA + H2O H3O+ + A-. This is because the Ka value represents the acidity constant of an acid, which is the ratio of the concentration of the dissociated form (H3O+ and A-) to the concentration of the undissociated form (HA). Therefore, the equation that includes both the dissociated and undissociated forms of HA is the one that corresponds to Ka.

Explanation
The pH of a solution is a measure of its acidity or alkalinity. It is calculated using the formula pH = -log[H+]. In this case, the concentration of H+ ions is given as 0.0025 M. Taking the negative logarithm of this value gives a pH of 2.60.

Explanation
The molarity of hydroxide ion in an aqueous solution can be calculated using the equation: pOH = -log[OH-]. Rearranging the equation, we get [OH-] = 10^(-pOH). Plugging in the given pOH value of 5.33 into the equation, we get [OH-] = 10^(-5.33) = 4.7 x 10^(-6). Therefore, the molarity of hydroxide ion in the solution is 4.7 x 10^(-6).

Explanation
The base dissociation constant (Kb) is a measure of the strength of a base. It is the equilibrium constant for the reaction of the base with water to form the conjugate acid and hydroxide ions. In this case, ethylamine (C2H5NH2) is a base, and its Kb value is given as 6.4 x 10-4. To find the [H+] in a solution of ethylamine, we need to calculate the concentration of hydroxide ions (OH-) using the Kb value. Since water is amphoteric, the concentration of [OH-] will be equal to the concentration of [H+]. Therefore, the [H+] in the solution of ethylamine is 3.5 x 10-12 M.

Explanation
The pH of a solution is a measure of its acidity. A pH of 10.7 indicates that the solution is basic. In the given question, NaZ is the sodium salt of HZ, which means it is a conjugate base of the weak acid HZ. The Ka value represents the acid dissociation constant, which indicates the extent to which an acid dissociates in water. Since the solution is basic, it means that the concentration of the conjugate base (NaZ) is higher than the concentration of the weak acid (HZ). The Ka value for HZ will be relatively small, indicating that it is a weak acid. Among the given options, 6.0 x 10-9 is the closest value to represent a weak acid.