look at some examples, and see if you can figure out what an acid is… hcl (hydrochloric acid) hno...

Look at some examples, and Look at some examples, and see if you can figure out see if you can figure out what an acid is…what an acid is…

HCl (Hydrochloric acid)HCl (Hydrochloric acid)

HNOHNO3 3 (Nitric acid)(Nitric acid)

HH22SOSO44 (Sulfuric acid) (Sulfuric acid)

HH33POPO44 (Phosphoric acid) (Phosphoric acid)

Official definition:Official definition:(or one of the definitions, anyway)(or one of the definitions, anyway)

Acids are substances that give away hydrogen Acids are substances that give away hydrogen ions.ions.

Example: HCl gives away hydrogen to water: Example: HCl gives away hydrogen to water:

HCl (aq) + HHCl (aq) + H22O O H H33O+ (aq) + Cl- (aq)O+ (aq) + Cl- (aq)

Draw the hydrogen ion. What does it consist of?Draw the hydrogen ion. What does it consist of?

A hydrogen ion is simply A hydrogen ion is simply a proton.a proton.

Acids are also called “proton donors.”Acids are also called “proton donors.”

Tell-tale signs of an acid:Tell-tale signs of an acid:

sour tastesour taste(orange juice and lemonade contain (orange juice and lemonade contain

citric acid)citric acid) turns litmus paper redturns litmus paper red (by reacting with a chemical in (by reacting with a chemical in the litmus paper)the litmus paper) reacts with metals to producereacts with metals to produce

hydrogen gashydrogen gas

Examples of acids:

• Vinegar

• Lemon Juice

• Soft Drink

• Battery Acid

• Stomach Acid

• Apple Juice

• Black Tea

Chemists write the formulas for acids Chemists write the formulas for acids with the H at the front, so they’re easy with the H at the front, so they’re easy to identify as acids:to identify as acids:

HCl (Hydrochloric acid)HCl (Hydrochloric acid)

HNOHNO3 3 (Nitric acid)(Nitric acid)

HH22SOSO44 (Sulfuric acid) (Sulfuric acid)

HH33POPO44 (Phosphoric acid) (Phosphoric acid)

An acid is a proton donorA base is a proton acceptor

acidbase

Acids and Bases: Acids and Bases:

An acid is a compound that donates H+ An acid is a compound that donates H+ ions:ions:

HCl + HHCl + H22O O H H33OO++ + Cl- + Cl-

A base is a compound that accepts H+ A base is a compound that accepts H+ ions. In the equation above, water is ions. In the equation above, water is acting as a base.acting as a base.

btw: Hbtw: H33OO++ is called the hydronium ion is called the hydronium ion

Looking at the last Looking at the last two reactions, notice two reactions, notice that water acted as that water acted as an acid in one, and as an acid in one, and as a base in the other.a base in the other.

Substances that can act as an Substances that can act as an acid or a base are calledacid or a base are called

amphoteric.amphoteric.

Tell-tale signs of a base:Tell-tale signs of a base:

bitter tastebitter taste slippery feelslippery feel turns litmus paper blueturns litmus paper blue

(Conveniently, base, bitter, and blue all (Conveniently, base, bitter, and blue all start with B!)start with B!)

Examples of bases:

• Detergent

• Baking Soda

• Drain Cleaner

• Ammonia

• Soaps (hand, dish)

• Antacid

• Conjugate acids and bases:

• Acids and bases are identified based on whether they donate or accept H+.

• Remember, though, most reactions are reversible. Look at the reverse reaction. Can you identify an acid and base in the reverse reaction?

+Cl HH

HO

+H

HH O Cl+

acid base

• Conjugate acids and bases:

• Acids and bases are identified based on whether they donate or accept H+.

• “Conjugate” acids and bases are found on the products side of the equation. A conjugate base is the same as the starting acid minus H+.

+Cl HH

HO

+H

HH O Cl+

acid base conjugate acid conjugate base

conjugate acid-base pairs

Conjugate Acids and Bases: Conjugate Acids and Bases:

The Bronsted-Lowry definitions:The Bronsted-Lowry definitions:

HCl + HHCl + H22O O H H33OO++ + Cl + Cl--

The forward reaction is a reaction between The forward reaction is a reaction between an acid (HCl) and a base. The reverse an acid (HCl) and a base. The reverse reaction is also a reaction between an reaction is also a reaction between an acid (Hacid (H33O+) and a base.O+) and a base.



After the acid HCl donates its proton, it becomes After the acid HCl donates its proton, it becomes a base (Cl-). A a base (Cl-). A conjugate baseconjugate base is the is the substance that results after an acid donates a substance that results after an acid donates a hydrogen ion to a base.hydrogen ion to a base.

It’s a base, because it could take the HIt’s a base, because it could take the H++ back back again. And what do we call something that can again. And what do we call something that can take Htake H++??



After the water accepts the H+ ion from After the water accepts the H+ ion from HCl, it becomes HHCl, it becomes H33O+, the O+, the conjugateconjugate acidacid that can donate a proton. that can donate a proton.

Every acid-base interaction involves Every acid-base interaction involves conjugate acid-base pairs.conjugate acid-base pairs.

Think of it like playing catch, with the Think of it like playing catch, with the H+ ion as the baseball. When you have H+ ion as the baseball. When you have it, you’re the acid, after you throw it, it, you’re the acid, after you throw it, you’re the conjugate base.you’re the conjugate base.

Who is the acid, and who is the base?

Acids and Bases: Acids and Bases: SummarySummary

AcidAcid – H – H++ donor donor basebase – H – H++ acceptor acceptor acid-base reactionacid-base reaction acid + base acid + base conjugate base + conjugate acid conjugate base + conjugate acid

conjugate acidconjugate acid – what base becomes after it – what base becomes after it accepts Haccepts H++

conjugate baseconjugate base – what acid becomes after it – what acid becomes after it donates Hdonates H++

Practice problems 1 and 2:Practice problems 1 and 2:Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs:

acid base conjugate acidconjugate baseHC2H3O2(aq) + H2O(l) C2H3O2

–(aq) + H3O+(aq)


acidbase conjugate acidconjugate baseOH

–(aq) + HCO3–(aq) CO3

2–(aq) + H2O(l)


Practice: Identify the Practice: Identify the conjugate acid-base pairs conjugate acid-base pairs in these reactions:in these reactions:

33. NH. NH44++ + OH + OH-- NH NH33 + H + H22OO

4. 4. HSOHSO44-- + H + H22O O H H33OO++ + SO + SO44

2-2-

acid base conjugate acidconjugate baseHF(aq) + SO3

2–(aq) F–(aq) + HSO3–(aq)


acidbase conjugate acidconjugate baseCO3

2–(aq) + HC2H3O2(aq) C2H3O2–(aq) + HCO3

–(aq)


acid base conjugate acidconjugate baseH3PO4(aq) + OCl

–(aq) H2PO4–(aq) + HOCl(aq)


(5)

(6)

(7)

Neutralization reactions:Neutralization reactions:If you combine an acid with If you combine an acid with a base…a base…

Predict the products:Predict the products:

HCl + NaOH HCl + NaOH ? ?

Hint: It’s a special kind of double replacement Hint: It’s a special kind of double replacement reaction!reaction!

If you combine an acid with If you combine an acid with a base…a base…

HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl

This is called a This is called a neutralization reactionneutralization reaction because the acid and base neutralize because the acid and base neutralize each other.each other.

If you combine an acid with If you combine an acid with a base…a base…

HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl

The products of any neutralization reaction The products of any neutralization reaction are water and a salt.are water and a salt.

Acid/Base reactions:

Produce water and a salt (and sometimes carbon dioxide).

Hint: concentrate on the water first. Remember, water has the formula HOH.

Complete and balance the following:

HCl + KOH

HCl + Ca(OH)2

HOH + KCl

2

Require equal numbers

2HOH + CaCl2

1. Ba(OH)2 + H3PO4

2. HC2H3O2 + NaOH

3. H2SO4 + KOH

4. H2CO3 + NaOH

Everyday application:Everyday application:

The stomach secretes acids to help digest The stomach secretes acids to help digest foods. These acids, which include foods. These acids, which include hydrochloric acid, have a molarity of about hydrochloric acid, have a molarity of about 0.1M.0.1M.

Antacids, like Tums, Maalox, Mylanta and Alka-Antacids, like Tums, Maalox, Mylanta and Alka-seltzer are simple bases that neutralize seltzer are simple bases that neutralize stomach acids.stomach acids.

Naming acidsNaming acids

Look at the names of these acids – can Look at the names of these acids – can you come up with the rule?you come up with the rule?

HH22SOSO44: sulfur: sulfuricic acid acid

HNOHNO33: nitr: nitricic acid acid

HH33POPO44: phosphor: phosphoricic acid acid

Naming acidsNaming acidsRule #1: If the acid comes from a Rule #1: If the acid comes from a

polyatomic ion that ends in “ate,” the acid polyatomic ion that ends in “ate,” the acid is named ____-ic.is named ____-ic.

HH22SOSO44: sulfur: sulfuricic acid (from sulfate) acid (from sulfate)

HNOHNO33: nitr: nitricic acid (from nitrate) acid (from nitrate)

HH33POPO44: phosphor: phosphoricic acid (from phosphate) acid (from phosphate)


Rule #1: If the acid comes from a Rule #1: If the acid comes from a polyatomic ion that ends in “ate,” the acid polyatomic ion that ends in “ate,” the acid is named ____-ic.is named ____-ic.

Practice: What is –Practice: What is –

HCHC22HH33OO22??

HClOHClO33??

HH22COCO33??


Rule #2: If the acid does not have oxygen Rule #2: If the acid does not have oxygen in it, then name it…in it, then name it…

hydro + second element + ichydro + second element + ic

Example:Example:

HCl is hydrochloric acid.HCl is hydrochloric acid.

What would HBr be? HWhat would HBr be? H22S?S?

Acids and Bases: Acids and Bases: StrengthStrength

What makes an acid a strong acid?What makes an acid a strong acid?It ionizes completely in water!It ionizes completely in water!

These are strong acids (in order of increasing These are strong acids (in order of increasing strength):strength):

1.1. HNOHNO33 (nitric acid) (nitric acid)2.2. HCl (hydrochloric acid)HCl (hydrochloric acid)3.3. HBr (hydrobromic acid)HBr (hydrobromic acid)4.4. HI (hydroiodic acid)HI (hydroiodic acid)5.5. HH22SOSO44 (sulfuric acid) (sulfuric acid)6.6. HClOHClO44 (perchloric acid) (the strongest) (perchloric acid) (the strongest)

Strong acids:Strong acids:


Remember, strong acids ionize completely in water. The reaction goes all the way to the right. A single arrow is used. There are virtually no HCl molecules left intact.

Strong acids:Strong acids:


Looking at the equation above, with the single arrow, is Cl- a strong base or a weak base?

General ruleGeneral rule: The : The conjugate base of a conjugate base of a strong acid is a weak strong acid is a weak base.base.Similarly, the conjugate Similarly, the conjugate acid of a strong base is a acid of a strong base is a weak acid.weak acid.

One more reminder:One more reminder:

“Weak” does not mean the same “Weak” does not mean the same thing as “diluted.”thing as “diluted.”

HCl, for example is always a strong HCl, for example is always a strong acid. If you add 1000 liters of water acid. If you add 1000 liters of water to it, it will be diluted, but still to it, it will be diluted, but still strong because what little there is strong because what little there is will be will be completely dissociated.completely dissociated.

Electrolytes:Electrolytes:

Acids and bases are both examples of Acids and bases are both examples of electrolytes.electrolytes.

Electrolytes are compounds that form ions Electrolytes are compounds that form ions when dissolved in water.when dissolved in water.

They’re called electrolytes because they They’re called electrolytes because they can conduct electricity through water.can conduct electricity through water.

More on electrolytes:More on electrolytes:If two wires connected to a If two wires connected to a light bulblight bulb and to a power and to a power

source are placed in a source are placed in a beakerbeaker of water, the light of water, the light bulb will not bulb will not glowglow. If an electrolyte, such as . If an electrolyte, such as sodium sodium chloridechloride, is dissolved in the water, the light , is dissolved in the water, the light bulb will glow because the solution can now bulb will glow because the solution can now conduct electricity. The amount of electric current conduct electricity. The amount of electric current that can be carried by an electrolyte solution is that can be carried by an electrolyte solution is proportional to the number of ions dissolved. proportional to the number of ions dissolved. Thus, the bulb will glow more brightly if the Thus, the bulb will glow more brightly if the amount of sodium chloride in the solution is amount of sodium chloride in the solution is increased. increased.

Practice QuestionsPractice Questions

Which of these could be Which of these could be used to determine used to determine whether a substance is a whether a substance is a base?base?

A Thermometer A Thermometer B Litmus paper B Litmus paper C Balance C Balance D Bunsen burnerD Bunsen burner

An element common to An element common to all acids is –all acids is –

a. chlorinea. chlorineb. hydrogenb. hydrogenc. oxygenc. oxygend. sodiumd. sodium

look at some examples, and see if you can figure out what an acid is… hcl (hydrochloric acid) hno...

Documents

acid hcl

acidbase interaction

h conjugate base

acid h3o

starting acid

proton donora base

h ions

hcl h2o h3o