Acids & BasesGuided NotesPage 1

Acids and Bases - Describing Acids and Bases

Mini-Project

Work with a partner. Organize the following formulas into two groups with five formulas in each group: HNO3, NaOH, H2SO4, H2CO3, Ca(OH)2, KOH, H8PO4, Mg(OH)2, NH3, H2O

Group1 / Group 2

Group One is ______.

Group Two are ______.

Where do NH3 and H2O fit? Why or Why Not?

  • ______Models
  • A model is a way to ______or ______things that can’t be seen.
  • There are ___ common models
  • We will learn 2
  • ______Model (Oldest, most easily understood)
  • ______Model

Historical views on acids

The Bronsted-Lowry concept

  • ______(e.g. H2SO4) was originally thought to cause acidic ______. Later, ______was implicated, but it was still not clear why ______was neutral.
  • ______made the revolutionary suggestion that some solutions contain ______& that acids produce ______ions in solution.
  • The more recent ______concept is that acids are ______donors and ______are proton ______

______Model of Acids/Bases

  • Substance is an ______if it contains ______and _____ causes ______to form in solution
  • Dissociation means to ______
  • Substance is a ______if it contains a ______and dissociates to produce ______in solution

Arrhenius Model

ACIDS

Are Always ______in solution

Taste ______(lemon, vinegar)

React with ______to (______)

React with ______(makes bubbles of CO2)

Turns blue litmus ______

In Water forms ______ION (or ______ion)

BASES

Are ALWAYS ______in solution

Taste ______(soap, tonic water)

Feel ______(soap)

Turns Red Litmus ______

React with ______to make water

Why are Some Solutions Acid & Others Base?

  • Acid solutions contain ______ions than ____ ions.
  • Not ______OH- ions
  • Base solutions contain more ______ions than ______ions.
  • Not ______H+ ions
  • Water is the ______for Acid/Base and is defined as ______
  • Water has ______amounts of H+ and OH- ions (______)

Bronsted-Lowry Model

  • Acid is a ______(hydrogen ion) ______
  • Base is a ______(hydrogen ion) ______
  • This is a ______definition than Arrhenius model because there are substances that cause donation or reception ______having hydrogen in them.
  • Which items from our list fit this definition but not Arrhenius? ______and ______

Example

  • When an______dissolves in water, it donates an ______ion to a ______molecule forming H3O+(hydronium ion).
  • The ______molecule acts as a Bronsted-Lowry ______and accepts the H+ ion
  • HX + H2O ⇄H3O+ + X-
  • ______= species produced when a base accepts a hydrogen ion from an acid
  • ______= species produces when an acid donates a hydrogen ion to a base
  • Conjugate base ______= ____ substances related to each other by ______and ______a single hydrogen ion
  • In Bronsted-Lowry Model, every ______and every ______must have a corresponding conjugate ______or conjugate ______.
  • A conjugate Base is an ______that is ______a ______ion.
  • A conjugate acid is a ______that has an ______ion.
  • The ______becomes the conjugate ______
  • The ______becomes the conjugate ______.

Conjugate Acid/Base Practice problems

HC2H3O2(aq) + H2O(l)  C2H3O2–(aq) + H3O+(aq)

______

OH –(aq) + HCO3–(aq) CO32–(aq) + H2O(l)

______

HF(aq) + SO32–(aq) F–(aq) + HSO3–(aq)

______

CO32–(aq) + HC2H3O2(aq) C2H3O2–(aq) + HCO3–(aq)

______

H3PO4(aq) + OCl–(aq) H2PO4–(aq) + HOCl(aq)

______

Amphoteric = substances like water that can act like ______an ______or a ______

Monoprotic and Polyprotic Acids

______– acids based on formula that can donate only one hydrogen ions

CH3COOH + H2O ⇄ H3O+ + CH3COO-

______– acids that can donate multiple hydrogen ions

H3PO4 + H2O ⇄ H3O+ + H2PO4+

H2PO4+ + H2O ⇄ H3O+ + HPO4+2

HPO4+2 + H2O ⇄ H3O+ + PO4+3

______= oxides that can become acids or bases by adding elements contained in water

Acid Rain

Acid rain comes from rain collecting ______from the air to create acids:

Carbon Dioxide = ______acid

Sulfur oxides = ______or ______acid

Nitrogen oxides = ______acid

Damages ______, ______, kills______, kills ______

Acids and Bases in Solution

Chapter 19.2

Acid/Base Strength

In strong acids, almost all molecules ionize.

In weak acids, fewer molecules ionize.

Conjugate Pairs Strength

If an acid is a strong acid, its conjugate pair base is a weak base

Why?

If HX is strong acid, it ionizes completely.

The conjugate base must be a weak base because it has a greater attraction to the H+ than HX

The reaction equilibrium lies far to the right of the equation.

Conjugate Pair Strength

For a weak acid, the equation equilibrium lies to the right (reactant side)

Conjugate base (Y-) has a stronger attraction for the H+ ion than the base H2O

HY + H2O H3O+ + Y-

Acid Ionization Constants

An “ionization constant” is the tendency of an item to make ions in solution.

Higher the constant, the higher the amount of ions.

Acid ionization constant is value of the equilibrium constant expression for a weak acid

Value Ka indicates whether reactants or products are favored at equilibrium

Weak acids have low Kavalues

Acid Ionization Constants

Base Ionization Constant

Same Basic Principle as Acid

Measures OH- concentrations

pH Scale

Chapter 19.3

Ionization Constant for Water

The ionization constant for water is:

1.0 x 10-14

[Ka][Kb]

= [1.0x10-7] [1.0 x 10-7]

Experiments show that the product of [H+] and [OH-] always equals 1.0 x 10-14 at 298°C

pH scale is a way of showing this relationship of ionization constants

The pH Scale

pH stands for ‘per Hydrion’

Low pH is Acid

High pH is base

Water is neutral (7.0)

pH

There are many ways to consider acids and bases. One of these is pH.

[H+] is critical in many chemical reactions.

A quick method of denoting [H+] is via pH.

By definition pH = – log [H+], [H+] = 10-pH

The pH scale, similar to the Richter scale, describes a wide range of values

An earthquake of “6” is 10 as violent as a “5”

Thus, the pH scale condenses possible values of [H+] to a 14 point scale (fig. 2, p370)

Also, it is easier to say pH = 7 vs. [H+] = 1 x 10–7

pH

pH = -log [H+]

[H+] = 10-pH

pOH = -log [OH-]

pH + pOH = 14

Calculations with pH

Q: What is the pH if [H+]= 6.3 x 10–5?

pH = – log [H+]

‘(-)’, ‘log’, ‘6.3’, ’10x’, ‘(-)’, ‘5’, ‘)”, ‘)”, ‘ENTER’)

Calculating pH from Strong Acid Solutions

Strong acids are 100% ionized

For monoprotic acids, concentration of the acid IS the concentration of the H+ ion

Use Acid concentration as substitute for H+ ion concentration.

Use Base concentration as substitute for OH- concentration

Calculating pH from Strong Acid Solutions

Example: What is the pH of a 0.1M solution of HCl?

0.1 M HCl = 1 x 10-1 M

Calculate pH = 1

Example: What is pH of solution that is 7.5 x 10-4 M Ca(OH)2?

(7..5 x 10-4) x 2 = 1.5 x 10-3M

There are 2 OH- ions per molecule

Calculate pOH = -log[OH-]

= 2.8

pH = 14-2.8 = 11.2

Calculating Molarity from pH

Example: what is the molarity of an acid solution with a pH of 2.37?

[H+] = 10-pH

[H+] = 10-2.37 = 4.27 x 10-3 M

Neutralization

Chapter 15.4

Acid-Base Reactions

Neutralization reaction is a reaction between an acid and a base

Makes Water + Salt

Solution becomes Neutral (not acid or base)

Acid-Base Reactions

Mg(OH)2 + 2 HCl→MgCl2 + 2H2O

Note:

Cation from base (Mg) is combined with anion from acid (Cl)

The salt is MgCl2

The H+ and OH- always combine to form water

Acid-Base Titration

Acid/Base Titration is the stoichiometry of acid/base reactions.

Titration is a method for determining the concentration of a solution by using another solution of known concentration

Uses an INDICATOR to show when the acid/base reaction is complete (neutral)

Indicator is a chemical that changes color as determined by acid or base conditions

There are many indicators with different pH points.

Acid/Base Titration Curve

pH Indicators

Calculating Molarity from Titration

Write the balanced equation

Calculate the number of moles used in the ‘known’ solution

Use the mole ratio from the balanced equation to calculate moles of reactant in the ‘unknown’ solution

Calculate the molarity of the ‘unknown’ solution based on moles used and liters used.

Salt Hydrolysis

When you put salts in water, the resulting solution can be either acid, base, or neutral

Salts will dissolve to form ions

The anions will accept hydrogens from water

The cations will accept hydroxides from water

Which way it goes depends upon the strength of the conjugate acids/bases

If conjugate acid is strong, it will be acid

If conjugate base is strong, it will be base

If both are strong, it will be neutral

What are Buffers?

Buffers are solutions that resist changes in pH when limited amounts of acid or base are added.

Buffer is a weak acid and its conjugate base or a weak base and it’s conjugate acid

Buffer can accept or donate Hydrogen ions and shift its equilibrium point left or right

Buffers have limits, but the work for a while

Heavily used in human body, especially blood

Acid Names

Binary or hydrohalic acids–HF, HCl, HBr, HI, etc. “hydro____ic acid”are usually strong acids

If name ends in ‘-ide’

Acid name will be “hydro ____ic acid”

HF and H2S are weak hydrohalic acid. Although the H-F bond is very polar, the bond is so strong (due to the small F atom) that the acid does not completely ionize.

Acid Naming

Oxyacids–contain a polyatomic ion

Most common form (MCF) “ic”ending–strong acids (contain 2 oxygen per hydrogen)

If chemical name ends in “-ate”

Acid name will be “___IC Acid”

HNO3–nitric from nitrate

H3PO4 - phosphoricfrom phosphate

H2SO4 - sulfuricfrom sulfate

HClO3 - chloricfrom chlorate

Acids with 1 less oxygen than the MCF “ous”ending- weaker acids

Chemical name ends in “-ite”

Acid name is “___OUS Acid”

HNO2–nitrousfrom nitrite

H3PO3 - phosphorous from phosphite

H2SO3 - sulfurousfrom sulfite

HClO2 - chlorousfrom chlorite

c. Acids with 2 less oxygen than the MCF “hypo___ous”–very weak acids

HNO - hyponitrous

H3PO2 - hypophosphorus

HClO - hypochorous

d. Acids with 1 more oxygen than the MCF “per______ic”–very strong acids

HClO4–perchloric acid

HNO4 - pernitric acid

Organic acids –have carboxyl group -COOH- usually weak acids

Acid names are based on the base organic name or common name

HC2H3O2 - acetic acid

C7H5COOH - benzoic acid