Chapter 16 (sections 1-3) Flashcards
Define buffer
A solution containing significant amounts of both a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists pH change by neutralizing added acid or added base
A buffer resists pH change by _____ added acid or base.
neutralizing
A buffer contains significant amounts of …?
both a weak acid AND its conjugate base (or a weak base and its conjugate acid)
Buffers ____ pH change.
resist
A____ contains significant amounts of both a weak acid and its conjugate base
buffer
In a buffer the weak acid ____ added base until the concentration of the base…?
neutralizes
exceeds the concentration of the weak acid
In a buffer, the conjugate base ____ the added acid until the concentration of the acid …?
neutralizes
exceeds the concentration of the conjugate base
Define common ion affect
The tendency for a common ion to decrease the solubility of an ionic compound or to decrease the ionization of a weak acid or weak base
Using the approximation that x is small we can consider the equilibrium concentrationd of HA and A- to be essentially …?
identical to the initial concentrations of HA and A-
To determine the concentration of [H₃0⁺] for any buffer solution, we…?
multiply Ka by the ratio of the concentrations of the acid and the conjugate base
[H₃0⁺] = Ka [HA]/[A⁻]
In a buffer solution where the concentrations of the acid and conjugate base are equal what is [H₃0⁺] equal to?
Ka
When calculating the pH of a buffer, adding a small amount of strong acid to a buffer converts the stoichiometric amount of the _____ to the _____ ____
base
conjugate acid
When calculating the pH of a buffer, adding a small amount of strong base to a buffer converts the stoichiometric amount of the _____ to the _____ ____
acid
conjugate base
Define buffering action
The way a buffer solution reacts with small amounts of acid or base to maintain a fairly constant pH
pKa + pKb =..?
14
When is a buffer most effective?
When the concentrations of the acid and conjugate base are equal
A buffer becomes less effective as the difference in relative amounts of acid and conjugate base ______.
Increases
In order for a buffer to be reasonably effective, the relative concentrations of acid and conjugate base should not differ by more than a factor of _____.
10
A buffer is most effective (most resistant to pH changes) when the concentrations of acid and conjugate base are ____.
high
Lowest pH for effective buffers occurs when the base is one-tenth as concentrated as the acid. What is this in equation format?
pH = pKa -1
Highest pH for effective buffer occurs when the base is 10 times as concentrated as the acid. What is this in equation format?
pH = pKa + 1
The effective range for a buffering system is…?
one pH unit on either side of the pKa
Define buffer capacity
the amount of acid or base that can be added to a buffer without destroying its effectiveness
The buffer capacity increases with ____ absolute concentrations of the buffer components
increasing
