The pH of a 0.30-M solution of a weak base is 10.66 at 25 o C . The K b of the given base has to be calculated. Concept Information: Strong base and weak base: Strong base dissociates into its constituent ions fully. It produces more of hydroxide ions while dissolved in water. Weak bases partially dissociates into its constituent ions. According to Bronsted-Lowry, strong base is a good proton acceptor whereas weak base is a poor proton acceptor Since, the ionization of a weak base is incomplete; it is treated in the same way as the ionization of a weak acid. The ionization of a weak base B is given by the below equation. B (aq) +H 2 O (l) → HB + (aq) +OH - (aq) The equilibrium expression for the ionization of weak base B will be, K b = [ HB + ] [ OH - ] [ B ] Where, K b is base ionization constant, [ OH − ] is concentration of hydroxide ion [ HB + ] is concentration of conjugate acid [ B] is concentration of the base pOH definition: The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH - ] concentration. pOH scale is analogous to pH scale. pOH = -log[OH - ] Relationship between pH and pOH pOH is similar to pH . The only difference is that in pOH the concentration of hydroxide ion is used as a scale while in pH , the concentration of hydronium ion is used. The relationship between the hydronium ion concentration and the hydroxide ion concentration is given by the equation, pH + pOH = 14, at 25 o C As pOH and pH are opposite scale, the total of both has to be equal to 14.
The pH of a 0.30-M solution of a weak base is 10.66 at 25 o C . The K b of the given base has to be calculated. Concept Information: Strong base and weak base: Strong base dissociates into its constituent ions fully. It produces more of hydroxide ions while dissolved in water. Weak bases partially dissociates into its constituent ions. According to Bronsted-Lowry, strong base is a good proton acceptor whereas weak base is a poor proton acceptor Since, the ionization of a weak base is incomplete; it is treated in the same way as the ionization of a weak acid. The ionization of a weak base B is given by the below equation. B (aq) +H 2 O (l) → HB + (aq) +OH - (aq) The equilibrium expression for the ionization of weak base B will be, K b = [ HB + ] [ OH - ] [ B ] Where, K b is base ionization constant, [ OH − ] is concentration of hydroxide ion [ HB + ] is concentration of conjugate acid [ B] is concentration of the base pOH definition: The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH - ] concentration. pOH scale is analogous to pH scale. pOH = -log[OH - ] Relationship between pH and pOH pOH is similar to pH . The only difference is that in pOH the concentration of hydroxide ion is used as a scale while in pH , the concentration of hydronium ion is used. The relationship between the hydronium ion concentration and the hydroxide ion concentration is given by the equation, pH + pOH = 14, at 25 o C As pOH and pH are opposite scale, the total of both has to be equal to 14.
The pH of a 0.30-M solution of a weak base is 10.66 at 25oC. The Kb of the given base has to be calculated.
Concept Information:
Strong base and weak base:
Strong base dissociates into its constituent ions fully. It produces more of hydroxide ions while dissolved in water. Weak bases partially dissociates into its constituent ions.
According to Bronsted-Lowry, strong base is a good proton acceptor whereas weak base is a poor proton acceptor
Since, the ionization of a weak base is incomplete; it is treated in the same way as the ionization of a weak acid.
The ionization of a weak base B is given by the below equation.
B(aq)+H2O(l)→HB+(aq)+OH-(aq)
The equilibrium expression for the ionization of weak base B will be,
Kb=[HB+][OH-][B]
Where,
Kb is base ionization constant,
[OH−] is concentration of hydroxide ion
[HB+] is concentration of conjugate acid
[B] is concentration of the base
pOH definition:
The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH-] concentration. pOH scale is analogous to pH scale.
pOH=-log[OH-]
Relationship between pH and pOH
pOH is similar to pH. The only difference is that in pOH the concentration of hydroxide ion is used as a scale while in pH, the concentration of hydronium ion is used.
The relationship between the hydronium ion concentration and the hydroxide ion concentration is given by the equation,
pH+pOH=14,at25oC
As pOH and pH are opposite scale, the total of both has to be equal to 14.