Acids And Bases Flashcards
Binary acids
-Have each atom attached to a nonmetal
Ex: HCL
Oxy acids
-have hydrogen and oxygen and another element typically a nonmetal
HxEOy
(H: hydrogen
O: oxygen
E: central nonmetal element
Ex: H2SO4 H3PO3
Carboxylic acids
-have COOH chain attached to a carbon chain
Ex: HCOOH, CH3COOH
Arrhenius, definition of acids and bases
Acids: acids ionize [Process of forming ions from neutral molecules, typically involving a chemical reaction] in water to produce H+ ions and anions
Ex: HCl ionizes in water and produces H+(aq) + CL-(aq)
Bases: basis disassociate [break apart into individual ions] in water to produce OH ions and cations
Ex: NaOH (it is an ionic compound)
In water, it disassociates completely and produces Na+ + OH-
Arrhenius acid base reactions
The H+ from the acid combines with the OH- from the base to make a molecule of H2O
The remaining cation from the base combines with the remaining anion from the acid to make a salt
Acid + base = salt + water
Ex: HCL + NAOH= NaCl + H2O
Bronsted Lowry definition
Acids: The acid is a H+ donor
Base: The base is a H+ acceptor
In a Bronsted acid base reaction , an H+ is transferred
-The acid is a H+ donor and the base is a H+ accepter
Amphoteric substances
-substances, I can either act as an acid or a base
Ex: HCO3- H2PO4-
Conjugate Acids and base
-an acid becomes a conjugate base after donating a proton (H+)
-A base becomes a conjugate acid after accepting a proton (H+)
Ex: HCL (acid) = donates a proton Cl- (conjugate base)
NH3 (base) = accepts a proton NH4+ (conjugate acid)
-conjugate bases, have one less proton, and one less positive charge than its acid
-Conjugate acids have one more proton and one more positive charge than its base
Strong acid strength
-a strong acid completely ionizes in water
-single arrows used
-acid disassociation equilibrium lies far to the right
Ex: HA produces H+ + A-
HA+ H2O produces H3O+ + A-
Ex: HCL HBR HI HNO3
Weak acid strength
-weak acids partially ionized in water
-acid disassociation equilibrium lies to the left
-Double arrows are used
Ex:
HF-+ H20 (double arrows) F-+H3O+
Ex: HF H2SO3 H2CO3
Strength of strong bases
-a strong base completely disassociates in water to form OH-
BOH(aq) produces B+ + OH-
Ex: NAOH LiOH KOH CA(OH)2
Weak bases: produce a small amount of OH- by accepting a proton from water to form OH- to reach equilibrium
Ex:
NH3 + H2O producers NH4+ + OH-
B+ H2O = HB+ + OH-
EX: NH3 CO3 CH3NH2
Acid ionization constant (Ka)
Ka = [A-] [H3O+]/[HA]
(reactants over products)
The larger, the KA, the stronger the acid
-strong acid disassociation goes to completion so no KA
Binary acid strength (H-X)
-the more electronegative X is the stronger the acid
-bond energy: the weaker the bond (lower bond energy) the stronger the acid
-Across the period: acidity increases from left to right
-Down a group acidity increases due to lower bond energy, even if electronegativity decreases slightly
strong acid: a strong acid occurs when the bond is easy to break due to low bond energy and X is very electronegative
(Weakest strongest): HF HCL HBR because Br has the lowest bond energy
Strength of oxy acids H-O-Y
-the more electronegative Y is the stronger the oxy acid
-Across a period (left-right) acidity increases because electronegativity increases, which makes the H-O bond weaker
-the more oxygen atoms attached to Y the stronger the oxy acid
Base ionization constant (Kb)
-larger KB = stronger base
Ex: B+ + H2O produces HB+ + OH-
Kb= [HB+] [OH-]/ [B]
How do you find KB?
Ka and Kb are related for conjugate acid based pairs by the equation KaxKb = Kw
To find Kb: Kw/Ka
Kw is a constant 1.0x10^-4) at a constant temperature
-with the change of temperature, Kw changes, but [H+] always = [OH-]
KW
- neutral solutions have equal concentrations of H3O+ and OH- ions
-acidic solutions have a larger concentration of H3O+ than concentration of [OH-]
-basic solutions have a larger concentration of OH- than concentration of H3O+
Ka and Kb
-the stronger and acid the weaker, the conjugate base
-the stronger a base the weaker the conjugate acid
Acidity and basicity of a solution
-Expressed by pH
ph = -log[H3O+]
[H3O+] = 10^-ph
Ph vs pOH
pOH= -log[OH^-]
[OH-] = 10^-pOH
pH + pOH = 14.00
Calculate pH of an acid solution
-in most cases, we are not given [H+] or [OH-], instead the concentrations of the acid or base is given
To calculate the pH of the solution first think of sources of [H+]
-there are two sources of H3O+ in an aq solution of an acid, the acid and the water.
-for strong acids like HCl, they disassociate completely so if the concentration of HCL = 0.10M then the concentration of H3O+ will also be 0.10M. ph = -log(0.10)
-weak acids do not disassociate completely so to calculate pH of a weak acid, set up an ice table, and assume the initial concentration of HA = 0
- Write Ka and substitute equilibrium concentrations
- Solve for X (concentration of H3O+)
- Once you solved X calculate pH.
When to use small K approximation
-When X is less than 5% after doing the 5% check
5% check = x/[HA] initial
If more than 5% then use the quadratic equation to solve for pH
a= 1
b= Ka
c = Ka x initial value
Percent ionization of a weak acid
-A week acid partially ionizes when dissolved in water
% ionization = [A-]/[HAi] x100
-because [A-]eq = [H3O+]eq (1:1 mole ratio)
% ionization = [H3O+]/[HAi]. x100
The higher the percent ionization, the stronger the acid
Calculations of basic solutions
-use Kb and pOH in calculations
Kb = kw/ka
-small x approximation if less than 5%
- If given ph find H3O and then use kw/ka to find [Oh] which is x
Acid-base properties of salt
-salts or water soluble ionic compounds
Ex: KF NaCl
-when salts dissolve in water, they disassociate form ions in solution
KF(s) disassociates K+ + F-
-the salt solution can be acidic neutral or basic
Ph neutral, anions
In general, the anion (A-) is the conjugate base of an acid HA
EX: Cl- is the conjugate base of HCL
-And an ion that is the conjugate base of a strong acid is pH neutral
Ex: Cl- is the conjugate base of a strong acid HCL, thus Cl- is pH neutral
NO3- is the conjugate base of a strong acid HNO3, thus NO3- is pH neutral
Anion as base
-an anion that is the conjugate base of a weak acid is a weak base
Ex: F- is the conjugate base of a weak acid (HF) thus F- is a weak base and hydrolyzes in water
F- + H2O = HF + OH
Cations as acids
-Group one and group 2 metal cations are all pH neutral
Ex: Na+ and K+ are the counter ions were strong base NaOH, thus Na+ and K+ our pH neutral
Small, highly charged metals are weak acids (Al3+) (Fe3+)
Classifying salts as acid or base
-a salt contains both a cation and an anion, to determine its pH:
- Salt in which neither the cation nor the anion act as an acid or a base for pH neutral solutions
Ex: NaCl KBr - Salt in which the cation is pH neutral, and the anion acts as a base forms basic solution.
Ex: NaF KNO2
- Salt in which the cation acts as an acid and the anion is pH neutral forms, acidic solution
Ex: AlCl3 FeCl3 NH4Br - Salt in which the cation acts as an acid and the anion act as a base can form acidic or basic solutions.
-Compare Ka and Kb
Ka>Kb = acidic
Ka < Kb = basic
Determine the pH of a salt
- Determine the acid and base property of the cation and anion
- Write the corresponding chemical equations.
- Set up ice table and write the expression of Ka or Kb to solve for x and pH
Polyprotic acid
-Polyprotic acids have two ionizable protons
Ex: H2SO3 H2SO4
Ka1>Ka2>Ka3
Calculation of Polyprotic acid
Given [H2A], how do we calculate [HA-] [H+] pH and [A2-]
- [HA-] [H+] and ph can be calculated from Ka1
[A2-] is calculated from the 2nd ionization equilibrium, where the final [HA-] [H+] from the first ionization is now the initial concentrations in the ice table
