Buffers, pH, Acids & Bases, Titrations, Ksp

What will the pH at the equivalence point be with a solution of a strong acid + strong base (less than 7, 7, greater than 7)

7

What will the pH at the equivalence point be with a solution of a weak acid + strong base (less than 7, 7, greater than 7)

Greater than 7

What will the pH at the equivalence point be with a solution of a strong acid + weak base (less than 7, 7, greater than 7)

Less than 7

pH’s that are lower than are 7 are (acidic/basic)

Acidic

pH’s that are greater than are 7 are (acidic/basic)

Basic

The higher the Ka value is, the more (acidic/basic) it is

Acidic

The lower the Ka value is, the more (acidic/basic) it is

Basic

What is the relationship of Ka, Kb, and Kw?

Ka x Kb = Kw

What does Ka represent?

acid dissociation constant

What does Kb represent?

base dissociation constant

What does Kw represent?

Dissociation constant of water

What is Kw’s value at 25°C?

1.0 × 10E-14

If Ka​ is large, is the acid stronger or weaker?

Stronger

If Kb is large, is the base stronger or weaker?

Stronger

What is the formula for calculating pH?

pH=-log[H3O+]

What is the formula for calculating pOH?

pH=-log[OH-]

How do you find [H3O+] from pH?

10^-pH

How do you find [OH-] from pOH?

10^-pOH

What is the relationship between pH and pOH

pH + pOH = 14

What do acids produce when ionized in water?

H+ or H3O+ ions

What do bases produce in aqueous solutions?

OH- ions

What determines strong bases?

Having OH- in their formulas and dissociating completely in water

What are anions of weak acids?

Weak bases

What happens when a soluble ionic compound of fluoride or carbonate is added to water?

It creates OH-, raising the pH

What are protonated cations of amines?

Weak acids that lower pH

What do Group 1 and Group 2 cations contribute to acid/base properties?

They are neutral

What do anions of strong acids with a -1 charge do in solution?

They are neutral and do not contribute to acid/base properties

What does “protonated” mean?

Adding a proton (H+) to a molecule or ion

When a base accepts a proton it forms what?

Its conjugate acid

How do weak bases generate OH- ions?

Weak bases react with water to form OH- ions and their conjugate acid

What is the role of acids in acid-base reactions regarding protons?

Acids are proton donors

What are amines?

Weak bases that have N atoms that react with H+

What table is used for weak acids/weak bases?

ICE tables

What table is used for strong acids/strong bases?

ICF tables

What happens to strong acids/strong bases when they dissolve in water?

They completely dissociate in water

What happens to weak acids/weak bases when they dissolve in water?

They partially dissociate in water

What are bases?

Substances that accept or take protons from substances

What are amphoteric molecules?

A species capable of reacting either as an acid or base

At a neutral pH what is the relationship between hydronium and hydroxide ions?

[OH-]=[H3O+]

Buffers are solutions that…

Resist changes in pH when an acid or base is added

Any added acid or base is neutralized by a…

Weak base or acid in the buffered solution

Once the limit of how much acid or base is added,

the pH changes

How can a buffer be formed using a weak base?

Mixing a weak base with a salt of its conjugate acid

How can a buffer be formed by using a weak acid?

Mixing a weak acid with a salt of its conjugate base

How can a buffer be formed by using a strong acid?

Mixing a strong acid with a weak base

How can a buffer be formed by using a strong base?

Mixing a strong base with a weak acid

What is pKa?

A measure that tells us how strong or weak an acid is in a solution

Indicators must change…

Within 2 pH units of equivalence point

What is a buffer capacity?

The amount of acid or base that a buffer can neutralize without consuming all of a buffer component

How can you tell when a high buffer capacity has occured?

When the buffer solution can neutralize a significant amount of added acid or base without a large change in pH

How can you tell when a low buffer capacity has occurred?

When the buffer solution can neutralize a small amount of added acid or base before a large change in pH

What is the equivalence point?

The point in which the right amount if titrant is added to complete the reaction

What is the endpoint?

The point in which the indicator changes color during titration

Weak acids DO NOT…

React with their conjugate base (HA + A- → NR)

Henderson—Hasselbalch equation

pH = pKA + log(base/acid)

Buffers should have a pH within ___ of the pKA of the ___

0-2 pH units of the pKA of the weak acid/base

What is Ksp?

Equilibrium constant of a solid substance dissolving in water to make an aqueous solution (its ions)

The ___ (higher/lower) the Ksp the more ___ (soluble/insoluble) it is

higher, soluble

What happens when a strong acid is added to a buffer solution of a weak acid and its conjugate base?

The strong acid provides H+, which reacts with the conjugate base, decreasing the base and increasing the weak acid

What happens when a strong base is added to a buffer solution of a weak acid and its conjugate base?

The strong base provides OH−, which reacts with the weak acid, decreasing the acid and increasing the conjugate base

What happens when a strong base is added to a buffer solution of a weak base and its conjugate acid?

The strong base provides OH−, which reacts with the conjugate acid, decreasing the conjugate acid and increasing the weak base

What is the general effect of adding a strong acid to a buffer of a weak acid and its conjugate base?

The conjugate base decreases, and the weak acid increases

What is the general effect of adding a strong base to a buffer of a weak acid and its conjugate base?

The weak acid decreases, and the conjugate base increases

What is the general effect of adding a strong base to a buffer of a weak base and its conjugate acid?

The conjugate acid decreases, and the weak base increases

What is the general effect of adding a strong acid to a buffer of a weak base and its conjugate acid?

The conjugate acid increases, and the weak base decreases

Are buffers associated with ICE or ICF tables?

ICE tables

Is Ksp associated with ICE or ICF tables?

ICE tables

When working with weak acid/weak base reactions, what table do you use? (ICE/ICF)

ICE tables (not fully dissociated)

When working with strong acid/strong base reactions, what table do you use? (ICE/ICF)

ICF tables (fully dissociated or before adding solutions)

How do you select an appropriate indicator for a weak acid-strong base titration?

Choosing an indicator with the pKa close to the pH at the equivalence point

For an acid-base reaction, an indicator should have a ___ that is ___ (before/after/near) the equivalence point

vibrant color change that is near the equivalence point

For an acid-base reaction, an indicator should have a pKA that is ___ of the pH at the equivalence point

within 2 digits

Strong bases have ___ in their formula

OH- ions (ex. KOH, NaOH)

Weak bases ionize with ___ to make ___ and ___

Weak bases ionize with water molecules to make OH- ions and a protonated form of the base (ex. NH3(aq) + H2O(l) = NH4+(aq) + OH-(aq)

What type of equation will a titration problem (weak acid/base) have up to the equivalence point?

Forward/one-way neutralization equation (ICF tables, ex. HA + OH- → H2O + A-)

What type of equation will a titration problem (weak acid/base) have at the equivalence point?

Equilibrium equation (ICE table, ex. HA + OH- → H2O + A-, then focus on the conjugate A- + H2O = HA + OH-)

What type of equation will a titration problem (weak acid/base) have after the equivalence point?

Forward/one-way neutralization equation (ICF tables, excess after neutralization)

If pH > pKA, is acid or base favored?

Base-favored [A-] > [HA]

If pH = pKA, is acid or base favored?

Neither, they are both equal

If pH < pKA, is acid or base favored?

Acid-favored [A-] < [HA]