Acid Base NotesHistory of Theory for Acids and Bases• Arrhenius, Svante  

– Swedish physical chemist (1859-1927) – one of the first who attempted to scientifically

___________________________________________________________________

• Arrhenius acid – substance that, when dissolved in water, _________________________________________________________

• _____________

• Arrhenius base – substance that, when dissolved in water, _________________________________________________________

• _____________

Examples of Arrhenius acid and base

Properties of Acids and BasesAcids- Properties • Aqueous solutions of acids are called electrolytes

• Have a ___________________________________________

• Conduct ______________________________________ -- some well, some poorly

• Cause some indicators, or chemical dyes, _________________________________________________________________

• React with many ____________________________________________________________________________________________

• React with bases containing hydroxide ions to form _____________________________________________________

• pH ____________________

Bases- Properties• ________________________________________________________________ -- some well, some poorly

• Taste _____________________________________________________________________

• Cause some indicators, or chemical dyes, to ____________________________________________________

• React with acids containing hydroxide ions to form salt and water

• pH __________________________________

Naming Acids and Bases• Acid takes the form of HX, where H is the ______________________________________________________ and X is a

____________________________________________________________________________

• Rules for naming– When the name of the anion (X) ends in “–ide”

- the acid name begins with _________________________________________ - then, replace “-ide” with “ –ic” and add the word “acid” to the end.

• Examples– HCl:

– HBr:

– When the anion name ends in “-ate”• the acid is named by replacing “-ate” with “–ic” and adding the word “acid” to the

end.

• Examples– H2SO4:

– HNO3:

– When the anion name ends in ”-ite”• the acid is named by replacing “-ite” with “-ous” , and adding the word “acid” to the

end.

• Examples:– -H2SO3:

– HNO2:

• Bases are named the same way as other ionic compounds – Example: NaOH= Sodium Hydroxide

- The __________________________________________is left the same

- The anion is found on our list of common polyatomic ions from the back of your periodic table

- ***One to know: NH3 = _____________________________________________

Problems with the Arrhenius Theory• Remember, Arrhenius said that….

– acids were substances that dissociated into H+ ions in solution (i.e. Hydrogen ion producer)

– bases were substances that dissociated into OH- ions in solution (i.e. Hyrdroxide ion producer)

• In reality, this definition works ______________________________________________

• This definition ____________________________________________________________________________________________

– baking soda NaHCO3 (a known base) ______________________________________________________________

____________________________________________

Bronsted-Lowry Theory of Acids and Bases• Acid – H+ donor (proton donor)

• Base – H+ acceptor (proton acceptor)

Water as an acid and a base• From the previous slide – water can act like acid _______________________________________________ or base

_____________________________________________________

– this is called__________________________________________________

– In the presence of an acid, water will __________________________________________________________

– In the presence of a base, water will ___________________________________________________________

– It is not surprising then that in pure water one molecule can donate a proton to another and water can act both like an acid and a base.

Hydrogen ions from water Self-ionization

– Hydrogen ions (hydronium ions) are often referred to as __________________________________

• These can be written as_________________________________________

– Self-ionization occurs very seldom, therefore the concentration ________________________________

____________________________________________________________________________________

Concentrations of H+ and OH- in Pure Water• Concentrations of hydrogen and hydroxide ions can be written several different ways

• For example, you have a sample of pure water whose concentration of H+ and that of OH- ions is 0.0000001 moles/ L, or 1.0 x 10-7 M – This can also be written as

•

•

– This means that these concentrations are _________________________________________________________

– Anytime the hydroxide and hydrogen ion concentrations are equal, the solution is called a

________________________________________________

• For aqueous solutions, the product of the hydrogen ion concentration and the hydroxide ion

concentration equals ___________________________________

• The product of these two ion concentrations is called the________________________________________________

_________________________________________

Not all solutions are neutral…..• Not all solutions are neutral. Solutions can be classified as acids or bases depending on their

• Acids

– [H+] > [OH-]

–

• Bases–

– [H+] < 1.0 x 10-7 M

• Example:– If the [H+] in a solution is 1.0 x 10-5 M, is the solution acidic, basic, or neutral? What is the

[OH-] of this solution?

The pH scale• Expressing the concentration of hyrdogen and hydroxide ions in molarity can be difficult at times

so scientists came up with another scale

• The pH scale– 0-14

– _____________________________________ have a pH of 7

– 0 is strongly ________________________

– 14 is strongly ______________________________

• The pH scale is like the Richter scale, which measures earthquakes. The change of 1 unit is a tenfold

• Meaning- an earthquake with a tremor measuring 4.0 is 10x greater than one measuring 3.0.

• You can convert the concentration of hydrogen and hydroxide ions in molarity to the pH scale

*****You must know all of these equations as well*****

• Log (A * B) = logA + logB

• Log (10x) = x

• pH= -log[H+]

• pOH= -log[OH-]

• pH + pOH = 14

Example– Find the pH of a solution with a hydrogen ion concentration of 1.0 x 10-10M

Example– The pH of a solution is 6.00. What is its hydrogen-ion concentration?

The reality is……• pH is normally not ________________________________________________________

• In this case we need a scientific calculator

• Example 1: What is the pH of a solution if [OH-] = 4.0 x 10-11M?– Solve by writing down your knowns and unknowns from the problem

Step # 1:– Known’s:

• [OH-]= 4.0 * 10-11M• KW= [H+] * [OH-] = 1.0 * 10-14

• pH = -log [H+]– Unknowns:

• pH=?• [H+]= ?

I want to find pH. So, pH= -log [H+] but, we don’t know the [H+]. We must find that first:

Step # 2: Find [H+]

– [H+] = 1.0 * 10 -14 = 0.25 * 10-3 M or 2.5 * 10-4

4.0 * 10-11

Step # 3: Find pH– Use pH= -log [H+]

• -log (2.5 * 10-4)• Remember: log (A * B) = logA + logB• = - (log2.5 + log10-4)• = -(0.40) - (-4)• = -0.40 + 4• = 3.60 pH

So, is this solution acidic or basic?

Example– What is the pH of a solution if [OH-] = 3.5 x 10-9 M?

Example-- Calculate the pH of a solution with a [OH-] of 7.5 x 10-8 M

• Fill in the table for a solution whose pH is 3.70.

pH pOH (H+) (OH-)3.7

Types of acids• Monoprotic acid

– Acids that contain ____________ ionizable hydrogenExample:

• Diprotic acid– Acids that contain ____________ ionizable hydrogens

Example:

• Triprotic acid– Acids that contain ____________ ionizable hydrogens

Example:

Neutralization Reactions• Acid-Base Reactions

– An acid reacts with a base to produce __________________________________________________________

– Examples (strong acids reacting with strong bases)

• HCl(aq) + NaOH(aq) è NaCl(aq) + H2O(l)• H2SO4(aq) + 2KOH(aq) è K2SO4(aq) + H2O(l)

• In the above examples there are __________________________________________ of hydrogen and hydroxide

ions, creating a ___________________________________________________.

• The final solutions have characteristics of __________________________________ an acidic or basic solution.

• Definition of a neutralization reaction– _________________________________________________________________________________________________________

_________________________________________________________________________________________________________

– A double-replacement reaction

– Neutralization will not necessarily occur between weak acids and/or weak bases (acids or bases that do not completely dissociate in solution).

Titration

– Process of adding a known amount of solution of a known concentration _____________________________

_________________________________________________________________________________________________________________

– Titrations are helpful because they ________________________________________________________________________

_________________________________________________________ and no longer retains acidic or basic properties. (i.e tells us the exact concentration of base needed to neutralize an acid.)

Steps for completing a titration:1. A measured volume of an acid solution of unknown concentration is added to a flask.2. Several drops of an indicator are added to the solution. 3. Measured volumes of a base of known concentration are mixed into the acid until the indicator

just barely changes color and maintains that color. This occurs at the “end point”.4. When you add a base or acid of known concentration to this solution, add it incrementally until

you reach the point at which the moles of H+ and OH– are equal. This is called the equivalence point. – Examples for strong acids and strong bases– When titration is complete at the end point, the contents of the flask are only salt and

water. This is a neutral solution.

• Titration Curves (This Curve is for Strong-Acid; Strong-Base Titration)• The end point (equivalence point) has a pH at or very close to pH = 7.

Example 1:

Titration Example 1:

Another Titration Example