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