MINI-TEST 4 STUDY GUIDE

Question 1

What is an Arrhenius Acid?

Answer 1

A substance that, when dissolved in water, increases the concentration of hydrogen ions (H⁺) in the solution

Question 2

What is an Arrhenius Base?

Answer 2

A substance that, when dissolved in water, increases the concentration of hydroxide ions (OH⁻) in the solution

Question 3

What is a Bronsted-Lowry Acid?

Answer 3

A substance that can donate a proton (a hydrogen ion H+)

Question 4

What is a Bronsted-Lowry Base?

Answer 4

A substance that can accept a proton (a hydrogen ion H+)

Question 5

What is Lewis Acid?

Answer 5

A substance that can accept a pair of electrons (2e-) to form a covalent bond
(ex: METAL IONS! Ag1+, Zn2+, Al3+)

Question 6

What is a Lewis Base?

Answer 6

A substance that can donate a pair of electrons (2e-) to form a covalent bond
(ex: LONE PAIR DONORS! NH3, H2O, OH-)

Question 7

How are salts most often formed?

Answer 7

NEUTRALIZATION REACTIONS: (BCA Table)
Acid + Base -> Salt + H2O
(HA + OH- -> A- + Water)

The positive ion (cation) of a base and the negative ion (anion) of an acid make up a salt.

Question 8

What is the definition of a salt? How else are salts formed?

Answer 8

A salt is an ionic compound composed of positively charged ions (cations) and negatively charged ions (anions), which are held together by ionic bonds.

Also formed by:
- Precipitation Reactions
- Acid-Metal Reactions
- Base-Metal Reactions
- Evaporation of Solutions

Question 9

Will all salts change the pH of water? which ones won’t?

Answer 9

NO! Strong Acid + Strong Base = Neutral Salt
- Cations of strong bases do not change pH
- Anions of strong acids do not change pH

Question 10

When weak acids undergo hydrolysis, what happens to the pH?

Answer 10

• Cations of weak bases lower the pH
  BECAUSE THEY’RE CONJUGATE ACIDS!
  (NH3 + H2O <-> NH4+ + OH-)
  ^
• Anions of weak acids raise the pH
  BECAUSE THEY’RE CONJUGATE BASES!
  (HCN + H2O <-> CN- + H3O+)
  ^

Question 11

How do positively charged polyatomic cations affect the pH?

Answer 11

Ions such as NH4+, H3O+, and NO2+ LOWER the pH BECAUSE THEY’RE ACIDS!

Question 12

How do metal ions affect the pH of a solution?

Answer 12

Metal ions (LEWIS ACIDS) generally make pH levels drop dramatically because they produce CONJUGATE ACIDS that increase H+ concentration through hydrolysis

Question 13

How can we know if a solution is acidic or basic when only given Ka and Kb values?

Answer 13

If Ka (of the cation) > Kb (of the anion)
Then SOLUTION IS ACIDIC

If Ka (of the cation) > Kb (of the anion)
Then SOLUTION IS BASIC

Question 14

What is a conjugate acid?

Answer 14

A species that is formed when a base gains a proton (H⁺), or the species that results from the addition of a proton to a base.

(HA) or (BH+) if A=Acid and B=Base

Question 15

What is a conjugate base?

Answer 15

A species that is formed when an acid loses a proton (H⁺), or the species that results from the removal of a proton from an acid.

(A-) or (B) if A=Acid and B=Base

Question 16

What is the difference between strong acids and bases and weak acids and bases?

Answer 16

Strong: completely dissociate in water, yielding high concentrations of either H+ (acids) or OH- (bases)
* Ka or Kb&raquo_space; 1

Weak: partially dissociate in water, yielding lower concentrations of either H+ (acids) or OH- (bases)
* Ka or Kb &laquo_space;1

STRONG ACIDS AND BASES ARE SUPER SOLUBLE! WEAK ONES ARE NOT

Question 17

What is the Autoionization of Water?
Why is this important?

Answer 17

The autoionization of water refers to the spontaneous reaction where water molecules react with each other to form hydronium ions (H₃O⁺) and hydroxide ions (OH⁻) in solution.

H2O + H2O <-> H3O+ + OH-
(acid) (base) (c.acid) (c.base)

(or H2O <-> H+ + OH-)

• pH = 7 *
  [H+] = [OH-]
  1E-7 = 1E-7

Question 18

What is kW equal to?

Answer 18

kW = [H+]*[OH-]
kW = 1E-7 * 1E-7
kW = 1E-14

Question 19

When must we account for the autoionization of water in an equilibrium reaction?

Answer 19

When pH is between 6 and 8 (when the initial concentration of either H+ or OH- are close to 1E-7)

Question 20

How can we account for the autoionization of water in an equilibrium reaction

Answer 20

We must add 1E-7

Question 21

What is pH? What is it equal to?

Answer 21

“potential” of Hydrogen ions: the measure of acidity of a solution

pH = -log[H+]
pH = 14 - pOH

Question 22

What is pOH? What is it equal to?

Answer 22

“potential” of Hydroxide ions: the measure of basicity of a solution

pOH = -log[OH-]
pOH = 14 - pH

Question 23

If pH = 4, then what does [H+] equal?

Answer 23

[H+] = 10^-4
(because pH = log[H+])

Question 24

If pOH = 10, then what does [OH-] equal?

Answer 24

[OH-] = 10^-10
(because pOH = log[OH-])

Question 25

What are the formulas for all 6 strong acids?

Answer 25

"I love to watch CSI on NBC" HCl HNO3 H2SO4 HBr HI HClO4

Question 26

What are the names for all 6 strong acids?

Answer 26

"I love to watch CSI on NBC" HCl: Hydrochloric Acid H2SO4: Sulfuric Acid HI: Hydroiodic Acid HNO3: Nitric Acid HBr: Hydrobromic Acid HClO4: Perchloric Acid

Question 27

What are the formulas and names for the 8 most common strong bases?

Answer 27

LiOH: Lithium Hydroxide NaOH: Sodium Hydroxide KOH: Potassium Hydroxide RbOH: Rubidium Hydroxide CsOH: Cesium Hydroxide Ca(OH)2: Calcium Hydroxide Sr(OH)2: Strontium Hydroxide Ba(OH2): Barium Hydroxide

Question 28

What happens to the conjugate base strength as acid strength increases?

Answer 28

As acid strength increases, conjugate base strength decreases.

Question 29

What happens to the conjugate acid strength as base strength increases?

Answer 29

As base strength increases, conjugate acid strength decreases.

Question 30

What is % Ionization?

Question 31

What are Polyprotic Acids? What do we have to keep in mind when dealing with them?

Question 32

What is pKa? What does a really negative pKa tell us?

Question 33

What is pKb? What does a really negative pKb tell us?

Question 34

What are the steps for setting up equilibrium reactions with weak acids and bases?

Answer 34

STEP 1: Write out what each substance dissolves into STEP 2: Determine which ion(s) react with water STEP 3: Write out equilibrium equation, excluding spectator ions * With salts you must consider dissociation of ions! (1. Ca(ClO)2 -> Ca2+ + 2ClO-) (2. ClO- + H2O <-> HClO + OH-)

Question 35

What makes a buffer?

Question 36

What is the relationship between pH and pKa in the context of indicators?

Question 37

What makes a substance soluble?

Question 38

What makes a buffer?

Answer 38

A mixture of a weak base (or weak acid) with its conjugate acid (or conjugate base) in solution.

Question 39

When can we use the Henderson Hasselbalch equation