Unit 8: Acids and Bases

Bronsted-Lowry Acid

substance that donates hydrogen ions (H⁺)

Bronsted-Lowry Base

substances that accept a hydrogen ion (H⁺)

single headed arrows

signifies the strong acid/base completely ionizes or dissolves

HCl, HBr, HI, HNO₃, H₂SO₄ (first H ion), and HClO₄

strong acids (SO, I BRought NO CLean CLOthes)

group 1 and group 2 metals with hydroxide

strong bases

water constant (K_w)

due to autoionization of water, [H⁺][OH^-] or 1.0 × 10^-14

y=10^-px

inverse of px= -log(y) formulas

temperature

only thing that can change an equilibrium constant

water pH and temperature relationship

as temperature increases pH of pure water decreases

electrolytes

can conduct electricity when they are in solution, strong acids/bases are strong these

acid is weaker

the smaller the K_a and the larger the pK_a

base is weaker

the smaller the K_b and the larger the pK_b

percent ionization

measurement of the extent of ionization, changes when molarity values change, increases as molarity decreases

lower percent ionization

when acids are of equal concentration, the weaker acid will have this

higher percent ionization

when two samples of same acid have different concentrations, the solution with lower concentration will have this

100% ionization

strong acids have this

[H₃O⁺]_equilibrium/[HA]_initial x 100

percent ionization formula

larger K_a

signifies a stronger pH

H attached to highly electronegative atoms

these atoms have a tendency to ionize when dissolved in water

more resonance structures

means that the conjugate base is more stabilized, which means the acid is stronger

inductive effect

the attraction of electrons in adjacent bonds by more electronegative atoms, makes bases less likely to accept a proton when this stabilizes conjugate acids

more electronegative atoms

when more of these are in a strucutre, the acid strength increases

oxo/oxyacids

contain an atom bonded to one or more O atoms, sometimes with H atoms attached

lower electronegativity

means a bond is stronger

buffer

a solution that contains a conjugate acid-base pair that are able to maintain the pH of a solution

half equivalence point

the point at which exactly half of the acid in the buffer solution has reacted with the titrant

amphoteric

a substance that can act as both an acid and a base

equivalence point

the point in a titration where the amount of titrant added is enough to completely neutralize the analyte solution, [H⁺]=[OH^-]

pH=7 at equivalence point

true for strong acid/strong base titrations

pH>7 at equivalence point

true for weak acid/strong base titrations

pH<7 at equivalence point

true for strong acid/weak base titrations

equimolar (at equivalence point)

means that a weak+strong titration is at its equivalence point

ways to make a buffer

partial neutralization of a weak and a strong, weak with the salt of its conjugate

diltuion

when volume is added to volume, anticipate this and use V₁M₁ = V₂M₂

pH=pK_a or pOH=pK_b

true at half equivalence point

pH<pK_a

means [base]<[acid]

pH>pK_a

means [base]>[acid]

pH=pK_a+1

means [base]/[acid]=10¹, which means there is 10 times more base than acid

pH=pK_a+2

means [base]/[acid]=10², which means there is 100 times more base than acid

pH=pK_a-1

means [base]/[acid]=10^-1, which means there is 10 times less base than acid

pH=pK_a-2

means [base]/[acid]=10^-2, which means there is 100 times less base than acid

indicator

used to see if a reaction has reached equivalence point, signifys via change in color, contain a molecule and its conjugate

color changes

typically occur 1 pH unit above or below the pK_a

pH=pK_a+log [base]/[acid]

Henderson-Hasselbalch equation for acid buffers

pK_a±1

buffering region

pOH=pK_b+log [acid]/[base]

Henderson-Hasselbach equation for weak base buffer

buffer capacity

amount of acid or base that can be added to a buffer system without the pH changing by more than a pH of 1

pH=pK_a or pK_b

optimal pH of a buffer

[acid]>[base]

the buffer has an increased capacity to deal with additional OH^- ions

(increased [acid])/ [base]

results in a lower pH and range but increases buffer capacity to deal with OH^-

[base]>[acid]

buffer has an increased capacity to deal with addition of H⁺ ions

(increased [base])/ [acid]

means higher pH and range but increases buffer capacity to deal with H⁺