Acids and Bases

Naming Acids

• Binary Acids- Contains H and one other element• Use the prefix hydro- and the root of the second

element (change end to “ic”) + acid• Examples:• HCl- hydrochloric acid HF- hydrofluoric acid • HI- hydroiodic acid HBr- hydrobromic

acid

• *Special case- for acids w/ 3 elements (polyatomic ions), but no O:

• Prefix hydro- and the root of the polyatomic ion (change end to “ic”) + acid

• HCN hydrocyanic acid

Naming acids, cont.

• Oxyacids- Contains an H and a polyatomic ion with an Oxygen – Use the root of the ion, add a suffix (ic or

ous), then acid

• **Do not use the prefix “hydro” for these!• When to use ic or ous:

– If the ion ends in “ate” = change end to “ic”

• Ex: HNO3 (anion = nitrate) = nitric acid– If the ion ends in “ite” = change end to “ous”

• Ex: HNO2 (anion = nitrite) = nitrous acid

Naming Bases

• Name of element + hydroxide

• Mg(OH)2 magnesium hydroxide

• KOH potassium hydroxide

• **H must be at the beginning of the formula to be an acid**

What is an acid?-- Sour taste

-- Turns blue litmus paper

pink

-- Makes a conjugate base

-- Reacts with some metals to make H2 gas

-- pH less than 7

-- More H+ ions than OH-

-- Conducts electricity

-- Usually dissolved/diluted in H2O

-- H+ ion donor in reactions

-- Donates an H+ to base

-- Sometimes water acts as the acid in the reaction

What is an acid?

Strong Acids

•Sulfuric Acid – H2SO4

•Hydrobromic Acid – HBr

•Hydrochloric Acid – HCl

•Nitric Acid – HNO3

•Ionize completely in reactions

•Reaction goes to completion (cannot go in reverse)

•Good conductors of electricity

•Make weak conjugate bases

Weak Acids

•Hydrofluoric Acid – HF

•Acetic Acid – HC2H3O2

•Hydrosulfuric Acid – H2S

•Carbonic Acid – H2CO3

•Ionize partially in reactions

•Reaction in equilibrium (can go in reverse)

•Does not conduct electricity well

•Make strong conjugate bases

What is a base?-- Bitter taste

-- Slippery to touch

-- Turns pink litmus

paper blue

-- More OH- ions than H+ ions

-- pH greater than 7

-- Makes conjugate acid in reactions

-- Accepts H+ from acid

-- Conducts electricity

-- Usually dissolved/diluted in H2O

-- Sometimes water acts as a base in reactions

What is a base?

Strong Bases

•Litihium hydroxide – LiOH

•Sodium hydroxide – NaOH

•Potassium hydroxide – KOH

•Magnesium hydroxide – Mg(OH)2

•Dissociate (dissolve) completely in water solutions to make metal ions and OH ions

•NaOH Na+ + OH-

•Make weak conjugate acids

Weak Bases

•Ammonia – NH3

•Aluminum hydroxide – Al(OH)3

•Iron (III) hydroxide – Fe(OH)3

•Partially dissociates in water solutions to make conjugate base and OH ions

•CH3NH2 + H2O ↔ CH3NH3+ + OH-

•Make strong conjugate acids

What are conjugate acids and bases?

-- Conjugate acid -- created when a base accepts an H+

-- Conjugate base – created when an acid donates (gives away) an H+

-- Creates a conjugate acid-base pair – 2 substances related to each other by donating/accepting H+ ions in a reaction

-- General equation for a acid-base reaction is:

HX + H2O H3O+ + X-

So, H2O and OH- are a conjugate acid-base pair and NH3 and NH4+ are

a pair as well.

EXAMPLES: Identify the acid/base/c. acid/c. base

NH3 + H2O NH4+ + OH-

NH3 + H2O ↔ NH4+ + OH-

HCN + H2O ↔ H3O+ + OH-

ACID BASE C. ACID C. BASE

Other things to know…-- Water is amphoteric, which means it can act as an acid or a base. It depends on what it reacts with that decides if it’s an acid or a base.

-- Monoprotic acids – only donate 1 H+ to the reaction

-- i.e. NH4 will become NH3 H2O will become OH-

-- Diprotic acids – donate 2 H+ to the reaction

-- i.e. H2SO4 will become SO42- H2CO3 will become

CO32-

-- Polyprotic acids – donate 3 or more H+ to the reaction

-- i.e. H3PO4 will become PO43-

-- The process of giving off H+ ions is called ionization

-- The model we use to identify acids/bases/c. acids/c. bases is called the BrØnsted-Lowry model of acids and bases

-- Strength does not mean concentration. Just because an acid is strong does not mean it has a high molarity concentration.

What is the pH scale?

-- The pH scale measures how acidic or basic a substance is.

-- pH greater than 7 is basic

-- pH less than 7 is acidic

Stom

ach acid

Battery acid

Soft d

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Tom

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s

Coffee

Milk

Pure

water

Bloo

d

Antacid

Soa

p/Detergen

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Milk of m

agnesia

Household

amm

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Hair rem

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Oven cleane

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pH (power of hydrogen)

•Acids, Alkalis and Neutralization

How do you calculate pH? FORMULA: pH = -log [H+]

Example 1: What is the pH of a solution with a [H+] of 1x10-2?

pH = - log (1x10-2)

= - (log 1 + log 10-2)

= - [0 + (-2)]

= - [-2]

= 2

Example 2: What is the pH of a neutral solution?

pH = - log (1x10-7)

= - (log 1 + log 10-7)

= - [0 + (-7)]

= - [-7]

= 7

How do you calculate pOH?

FORMULA: pOH = -log [OH-]

-- pOH is the concentration of the OH- ions in a solution

-- pH + pOH = 14

Example 1: Ammonia has an [OH-] concentration of 4.0x10-3. Calculate pOH and pH.

pOH = - log (4x10-3)

= - (log 4 + log 10-3)

= -[0.60 + (-3)]

= - (-2.40)

= 2.40

pH + 2.40 = 14

pH = 14-2.40

= 11.60

Acid Base Indicators -- Chemical dyes that change colors depending on their placement in an acidic or basic solution.

-- Some indicators may remain colorless in certain pH ranges.

-- Used in toys that change colors when water is added.

Indicators

Neutralization• Is a chemical

reaction between and acid and a base in an aqueous solution

• Usually a double replacement reaction

• Makes water and a salt

Neutralization Reactions-- Reaction where an acid and base react in an aqueous solution to

produce a salt and water

EXAMPLE: Mg(OH)2 + 2HCl MgCl2 + 2H2O

base acid salt water

MgCl2 made up by: Mg2+ from base and Cl- from acid

More Examples:

1. Write the salt and water formed from HCl reacting with NaOH.

HCl + NaOH NaCl + H2O

salt water

2. Write the equation and identify the acid, base, salt, and water formed when nitric acid reacts with cesium hydroxide.

HNO3 + CsOH CsNO3 + H2O

acid base salt water

More Practice…..

• 1) hydrobromic acid and calcium hydroxide

• 2) sulfuric acid and potassium hydroxide

• 3) acetic acid and ammonium hydroxide

Answers

• 1) 2HBr + Ca(OH)2 CaBr2 + H2O

• 2) H2SO4 + 2KOH K2SO4 + H2O

• 3) HCH3COO + NH4OH NH4CH3COO + H2O

Label as Acid, Base, or Salt

• A) Na2SO4

• B) Mg(OH)2

• C) Ba3(PO)4

• D) H3PO4

• E) HI

• F) Cu(OH)2

• G) CsCl