Acids and Bases Flashcards
Arrhenius theory
in aqueous solutions, electrolytes exist as ions
arrhenius acids
a compound that, when dissolved in water, increases the concentration of hydrogen ions (H+)
Arrhenius bases
bases dissolved in water that increase the concentration of OH- ions
what happens when Arrhenius acids and bases react
when they neutralize each other water and a salt is produced
what are issues presented by the arrhenius theory
acids and bases don’t necessarily have H and OH and it doesn’t discuss dealing with them
Bronsted-Lowry acids
proton donors
bronstead-Lowry bases
proton acceotirs
which theory includes the concept of conjugate acid/base pairs
bronstead-lowry
what is a conjugate acid/base
differ by 1 hydrogen proton
what happens when bronstead lowry acids dissolve in water
they protonate water -> formation of hydronium ions (H3O+)
what happens when bronstead lowry bases dissolve in water
they deproponate water to form hydroxide ions (HO-)
What is the lewis theory
focuses on the electron transfer between acids and bases (typically in the formation of covalent bonds)
What is the product of a lewis acid base reaction
an adduct
what is a lewis acid
lewis acids are electron acceptors, as they are electrophilic
what is a lewis acid
electron acceptors since they are electron deficient from being attached to electronegative atmos or not having full octets
what is required of lewis acids
they must have an empty orbital to accept an electron pair
what is a lewis base
electron donors since they have an extra lone pair it can donate
what makes a good lewis base
anion instead of neutral, and less electronegative as the lone pair will leave easier
which of lewis acids and bases are electrophiles
lewis acids
is water an acid or a base
both - it’s amphiprotic and can be either
what makes acids/bases strong
they essentially completely ionize in water
Kx of strong acids/bases
Ka/b»_space; 1 and reactions tend to run to completion
how does high K a/b affect pKa/b
higher K, lower pK
what are common strong acids
HCl, HBr, HI, HClO4, HNO3, H2SO4
what are common strong bases
OH + groups 1 or 2 but not top or bottom element
what does the strength of an acid depend on
the amount of ionization, which depends on the initial concentration of the acid and the value of Ka
what is Ka/b
the ionization constant
what is the relationship between strong acids/bases and weak bases/acids
the stronger the acid, the weaker its base
waht is a weak acid/base
only partially ionized in water
Ka/b of weak acids/bases
Ka/b «_space;1 so the equilibrium favours the products
what are common weak acids
acetic acid, nitrous acid, chlorous acid,benzoix acid, hydroflouric acid
what are common weak bases
ammonia, amines
how do metal ions with a +1 or +2 charge affect pH
they don’t, but +2 can act as an acid
how do polyatomic cations and anions act in water
anions often act as bases, while cations act as acids in water
what are binary acids
HnA = consists of hydrogen atoms and 1 other type of atom (A)
how does polarity of binary acids affect acid strength
the more polar the H-A bond, the stronger the acid
- acids in same period: the further to the right, the more polar, the stronger
how does the H-A bond strength affect acid strength
the weaker the H-A bond, the stronger the acid
- hydrogen bond strength decreases going across a group (left are stronger H bonds -> right are stronger acids)
what does the amount of ionization of an acid depend on
= the strength of the acid = the initial concentration of the acid and the ionization constant
how does the strength of a binary acid follow the periodic table
to the right and down is stronger acid from decreasing electron affinity/increasing electronegativity and decreasing H bond strength
HF strength
weaker than expected due to strong bond between hydrogen and fluorine from high electronegativity of fluorine
- makes it more difficult for HF to dissociate in water and donate H protons, making it a weaker acid than other hydrogen halides
organic acids
have alkyl chains like acetic acid and citric acid
organic acid strength
determined by electronegativity of neighbouring atoms and the stability of the conjugate base
organic base strength (amines)
depends on ability of the lone pair on N to bind to an H+
- electronegativity of neighbouring atoms and strength of conjugate acid
- substituent/alkyl groups with more connected carbons generally decreasing pKb, making the base stronger
what is protonating and its effect
protonating is the addition of a proton, leading to a loss of conjugation and a loss of stability
is the conjugate of a weak acid/base weak or strong
weak
is the conjugate of a strong acid/base weak or strong
extremely weak
what is percent ionization
another measure of acid strength, and varries with initial concentration of the weak acid unlike kA
what is the common ion effect in acid/base equilibrium
when a strong acid/base supplies the common ion, H3O+/OH- equilibrium shifts to form more HA/B
what is the effect of the ionization of a weak acid/base
the ionization is suppressed by either the conjugate base/acid or a strong acid/base
what is a buffer solution
contains appreciable amounts of both a weak acid and its conjugate base/both a weak base and its conjugate acid and has the ability to neutralize small quantities of either strong acids or bases
what is an acid buffer
maintains a ph < 7
what is a base buffer
maintains pH > 7
when is the henderson hasselbach eqn usable
for buffers when 0.1<[CB]/[CA]<10 and buffer has appreciable amounts of HA and A-
what are acid base indicators
weak acis/bases with different colours than their conjugates at their endpoints
what is an endpoint
the colour change of an indicator
what is an equivalence point
the point in a titration where the acid and base have completely neutralized each other
what is a titrant
the solution added with a known concentration in a titration
what is a titrand/analyte
the solution with an unknown concentration in a titration (added to)
what is a polyprotic acid
acids with more than one proton to donate (diprotic, triprotic, etc)
how many equivalence points does a polyprotic acid have
as many as protons to donate
what are zwitterions?
have both positive and negative charged groups
when does a dipolar zwitterion dominate
the isoelectic poin. = halfway between the pKa of ends
what type of ion is an amino acid
a zwitterion since NH2 (amine = base) is protonated and COOH (carboxylic acid) is deprotonated
