Question

question 5
to calculate the ph of a weak acid solution, you need to use
the arrhenius equation
gibbs free energy
an ice box
the integrated rate law
question 6
which one of the following can not be determined using the acid dissociation constant, ka?
ph
boiling point
hydronium ion concentration
poh

Explanation:

Question 5

• The Arrhenius equation is used to relate the rate constant of a reaction to the temperature and activation energy. It is not relevant for calculating the pH of a weak - acid solution.
• Gibbs free energy is related to the spontaneity of a reaction. It has no direct role in calculating the pH of a weak - acid solution.
• The integrated rate law is used to describe the concentration of reactants or products as a function of time for a chemical reaction. It is not used for pH calculations of weak - acid solutions.
• An ICE (Initial, Change, Equilibrium) box is used to set up the equilibrium expression for the dissociation of a weak acid (\(HA

ightleftharpoons H^{+}+A^{-}\)). By knowing the initial concentration of the weak acid and using its acid dissociation constant (\(K_{a}=\frac{[H^{+}][A^{-}]}{[HA]}\)), we can find the concentration of \(H^{+}\) ions. Then, using the formula \(pH =-\log[H^{+}]\), we can calculate the pH of the weak - acid solution.

• Using the acid dissociation constant \(K_{a}\) for a weak acid (\(HA

ightleftharpoons H^{+}+A^{-}\), \(K_{a}=\frac{[H^{+}][A^{-}]}{[HA]}\)), if we know the initial concentration of the acid (\([HA]_0\)) and assume \(x = [H^{+}]\) (for a monoprotic weak acid and under certain approximations), we can solve for \([H^{+}]\). Then, \(pH=-\log[H^{+}]\) and \(pOH = 14 - pH\) (at \(25^{\circ}C\) since \(pH + pOH=14\)). Also, \([H^{+}]\) (hydronium ion concentration) can be directly found from the equilibrium expression involving \(K_{a}\).

• The boiling point of a solution is a colligative property. It depends on the number of solute particles in the solution (for non - volatile solutes). The acid dissociation constant \(K_{a}\) is related to the degree of dissociation of an acid in solution, but not directly to the boiling point elevation formula (\(\Delta T_b=K_bm\), where \(K_b\) is the ebullioscopic constant and \(m\) is the molality of the solute).

Answer:

an ICE box

Question 6