A solution that lessens the impact on pH from the addition of acid or base.
A buffer must contain an ____________ component that can react with the added OH- ion and a ____________ component that can react with the added H3O+ ion.
Most commonly, the components of a buffer are the conjugate acid-base pair of a ________________.
Buffers work through a phenomenon known as the...
a given ion is added to an equilibrium mixture that already contains that ion, and the position of equilibrium shifts away from forming more of it.
The common-ion effect occurs when...
It consists of high concentrations of the acidic (HA) and basic (A-) components.
What is the essential feature of a buffer?
They cause a small amount of one buffer component to convert into the other, which changes the relative concentrations of the two components.
What happens when small amounts of H3O+ or OH- are added to a buffer?
Before the equivalence point in a weak acid-strong base titration curve there is a gradually rising portion of the curve called the ____________ region. At this point in the titration the weak acid and its ___________________ base are both present in the solution.
A buffer minimizes changes in pH when acid or base is added to the solution.
What is the function of an acid-base buffer?
A slightly soluble ionic compound will dissolve to a small extent in H2O and a saturated solution is formed at a fairly _______________ solute concentration. At this point there is a(n) ___________________ between undissolved solid and the dissociated ions in solution.
When Na2CO3 is added to a saturated solution of BaCO3, the equilibrium will shift by __________________ the amount of barium ions in the solution, thus _________________ the solubility of BaCO3.
The solubility of a slightly soluble ionic compound can be increased by adding a ligand (molecule or ion) that forms a(n) ________________ ion with the metal cation.
Adding a strong acid to a slightly soluble ionic compound will _____________ its solubility if it contains the anion of a weak acid.
Buffer _____________ is a measure of the ability of a buffer to maintain a PH following the addition of a strong acid or base.
decreases, higher, F-
In a 0.75 M HF solution, the HF is 2.2% dissociated. When NaF (s) is added to this solution the percent dissociation of HF _________________ and the pH of the resulting solution will be ____________________ than its original value. This effect is due to the addition of the common ion ___________________.
weak, conjugate, pH
An indicator is a(n) _______________ organic acid that has a different color than its __________________ base. Each indicator changes color over a specific, narrow ________________ range.
buffer, relative, one
The pH range over which the buffer is effective is called the _____________ range. This range depends on the ______________ concentrations of the buffer components, but is usually within +/- ___________ pH unit of the pKa of the acid component.
acid, base, stronger
A complex ion is formed between a metal ion, acting as a Lewis __________, and a ligand acting as a Lewis ____________. When the ligand is a ________________ Lewis base than H2O the metal ion will form a complex ion with the ligand rather than with water.
The more concentrated the components of a buffer, the ______________ the buffer capacity.
The ___________ of a buffer is distinct from its buffer capacity.
For a given addition of acid or base, the buffer-component concentration ratio changes (more or less) when the concentrations are similar than when they are different.
A buffer has the highest capacity when the component concentrations are _____________, that is, when [A-]/[HA] = 1.
A buffer whose pH is equal to or near the pKa of its ___________________________ has the highest buffer capacity.
The pH range over which the buffer acts effectively, and it is related to the relative component concentrations.
1. Decide on the conjugate acid-base pair.
2. Find the ratio of [A-]/[HA] that gives the desired pH, using the Henderson-Hasselbalch equation.
3. Choose the buffer concentration and calculate the amounts to mix.
4. Mix the amounts together and adjust the buffer pH to the desired value.
List the 4 steps on how to prepare a buffer.
Acid-base titration curve
A plot of pH vs. volume of titrant added.
A weak organic acid that has a different color than its conjugate base with the color change occurring over a specific and relatively narrow pH range.
An indicator changes color over a range of about _____ pH units.
The point at which the number of moles of added OH- equals the number of moles of H3O+ originally present.
Occurs when the indictor changes color.
We choose an indicator with an end point close to the ____________________________.
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