Acids and bases Flashcards
What are the three definitions for acid and bases?
- Arrhenius
- Bronsted-Lowry
- Lewis
What is the Arrhenius definition of acid-base?
Acid- will dissociate to form an excess H+ in solution
Base- Will dissociate to form an excess of OH- in solution
This is limited to aqueous acids and bases. they usually contain H in the beginning or OH at the end.
What a bronsted Lowry acid and base?
Acid- A species that donates H+ ions
Base- species that accepts H+ ions
It is not limited to aqueous solutions.
Usually occurs in pairs, called conjugate acid-base pairs
What is the Lewis acid-base definition?
Acid- an electron pair acceptor.
Base- electron pair donor
Different Names:
coordinate covalent bond formation, complex ion formation, nucleophile-electrophile interactions.
What are amphoteric species?
One that reacts like an acid in a basic environment and like a base in acidic environments.
What is an amphiprotic species?
In a Bronsted-Lowry, it can gain or lose a proton .
What are some amphoteric species?
Water, HSO4- also note Al, Zn, Pb, Cr, Zwitterions .
If an acid is formed from anions with names that end in -ide, the nomenclature is ?
Prefix hydro, ending ic
Oxyacids that end in -ite or ic have a nomenclature of?
end in -ous acid or ic acid respectively.
what is Autoionization?
When an amphoteric compound reacts with itself, like water.
What is Kw?
It is the water dissociation constant Kw= 10^-14. OH and H ions each 10^-7 if perfectly pure water
What is the equation for pH and pOH
pH= -log[H+]= log 1/[h+]
pOH=-log [OH-]= log 1/[OH-]
Concept understanding. -log( n x 10^-m) =
-log(n)-log(10^-m) = m - log(n), p value around m-0.n
What are strong acid and bases?
they completely dissociate in their component ions in aqueous solutions. They go to completion.
If the concentration of an acid or base is not far greater than 10^-7, what must one consider?
Autoionization of water. It is not negligible at this point (note ex on pg 339).
What are some strong acids?
HCl, Hbr, HI, H2SO4, HNO3, HClO4
What are some strong bases?
NaOH, KOH, soluble hydroxides of group IA.
What does it mean when a pH of a solution is greater than 14 or less than 0?
this implies there is a very high concentration of strong acids or bases.
What is the definition of weak acids and strong bases?
They partially dissociate in aq solutions.
What is the acid dissociation constant?
Ka = [H2O+][A-]/[HA] . the smaller Ka, the weaker the acid. Less than 1 is a weak acid
What is the base dissociation constant?
Kb = [B+][OH-]/[BOH] . the smaller b, the weaker the base and the less it will dissociate. less than one is a weak base.
How can the dissociation constant be determined if one species or conjugate is known.
Ka acid x Kb conjugate = Kw (10^-14) . vice versa too
When is approximation of x valid?
when x is less than 5% of the initial concentration or Ka is 100 times smaller.
What is neutralization reaction?
Acids and bases may react with each other to forma salt and often water(but not always). in general it is a process that goes to completion.
What is hydrolysis?
When salt ions react with water to give back the acid or base.
What occurs between a strong acid and strong base?
Products form equal molar amounts of the salt and base. They also neutralize each other and result in a pH of 7. They do not react with water because they are inert conjugates.
What happens when a weak base and strong acid react?
A salt is formed but often no water will be formed because weak bases are not hydroxides. The weak base can be reformed through hydrolysis.
What happens when a weak base and acid react ?
Depends on the relative strength of each, can go either way of the spectrum.
What is the the equation to calculate unknown titrand?
NaVa =NbVb . normality and volume.
What is the Henderson Hasselbalch equation
used to estimate pH or pOH of a buffer solution
pH=pKa + log [A]/[HA] . When conjugate base = weak acid, pH= pKa cause log 1 is 0. This occurs at half equivalence and is optimal. It quantifies the relationship between pH and pKa and vice versa.
How do you calculate the pH of a buffer when acid or base is added?
Calculate the the concentration in the final solution, NV=NV, then use the henderson equation.
What is equivalent?
It is defined as one mole of the species of interest .
What is normality?
The concentration of acid or base in equivalents solution.
What is polyvalent?
acid and base are those that can donate or accept multiple electrons. The normality of a solution containing polyvalent species is the molarity of the acid or base times the number of protons it can donate or accept.
What are titrations?
they are used to determine the concentration of a known reactant in a solution.
What is a titrant?
the concentration that is added slowly to the titrand
What is the titrand?
an unknown concentration but a known volume
What is the half-equivalence point?
it is the midpoint of the buffering region, in which half of the titrant has been protonated, or deprotonated. Thus HA=A- and buffer is formed
What is the equivalence point?
indicated by the sleepes slope in a atitration curve, it is reached when the number of acid equivalents in the original solution equals the number of base equivalents acid, or vice versa.
What are indicators?
they are weak acids or bases that display different colors in their protonated or deprotonated states. The indicator chosen should have a pKa close to the pH of the expected equivalence point. the endpoint of a titration is when the indicator reaches its final color.
If multiple buffering regions are observed, then …
it is polyvalent.
What are buffer solutions?
Consist of a mixture of a weak acid and its conjugate salt or vice versa, they resist large fluctuations in pH.
What are buffering capacities?
refers the ability of a buffer to resist changes in pH. Maximal buffering capacity is seen within 1 pH point of the pKa of the acid in the buffer solution.
