Ch. 2 - Acids & Bases Flashcards
What is a Bronsted-Lowry acid?
proton donor
What is a Bronsted-Lowry base?
proton acceptor
What must a BL acid have?
a hydrogen atom
What must a BL base have?
a lone pair or pi bond
What are counterions?
spectator ions (usually salts) that balance negative charge
What is the possible net charge of BL acids?
negative, positive or zero
What is the possible net charge of a BL base?
negative or zero
What is an oxyacid?
acid in which the protons are placed on the oxygen
What do you do when you see a salt in a reaction?
immediately split it into its ions and decide which ions are involved, make the other a spectator ion
What does a loss of a proton form?
conjugate base
What does the gain of a proton form?
conjugate acid
What does a starting material with a positive net charge indicate?
it is an acid
What does a starting material with a negative net charge indicate?
it is a base
What is acid strength?
the tendency of an acid to donate a proton
The stronger the acid, the ______ the Ka.
larger
The stronger the acid, the ______ the pKa.
smaller
What is the relationship between pKa and Ka?
pKa = -log(Ka)
What is the pKa range for a typical organic compound?
+5 to +50
What are the six strong acids? What are generally their pKas?
HCl, H2SO4, HBr, HNO3, HI, HClO4
negative pKas
What are the common strong bases?
NaOH, KOH, LiOH (anything with -OH)
How do you calculate Ka?
[products]/[reactants]
A strong acid forms a ______ conjugate base.
weak
A strong base forms a ______ conjugate acid.
weak
What does the position of equilibrium rely on in acid/base reactions?
strength of acid/base
equilibrium will favor the formation of the weaker acid/base
What is the general rule of acidity? (think stable!)
anything that stabilizes a conjugate base (A-) makes the starting acid more acidic
What is the pKa of acetic acid (weak acid)?
5
What is the pKa of water and alcohol?
16
What is the pKa of ammonia (weak base)?
38
What is the pKa of methyl amine?
40
What is the pKa of methane/ethane?
50
What are the four effects that make acids more acidic?
element, inductive, resonance, hybridization
What is the most important factor of acidity?
element effects
What are element effects?
the location of A (from HA) on the ptable
rows: acidity increases as A is more EN (right)
columns: acidity increases as A gets bigger (down)
What are inductive effects?
presence of atoms that are more electronegative than carbon
- withdraws electron density from C, pulls through sigma bonds
- stabilizes negative charge
» acidity INCREASES with presence of electron withdrawing groups (more EN, closer to neg charge, greater the effect)
What are resonance effects?
delocalization of electron density stabilizes conjugate bases and makes them weaker
acidity of HA increases when conj base is resonance stabilized
What are hybridization effects?
Lower hybridization (increased % s character) = more stable conj base and acid is more acidic
How many bonds are formed in an acid-base reaction?
one
Does an atom with a filled octet have an available electron pair?
no
Can unpaired electrons be used in acid-base reactions?
no
Equilibrium tends to the side with a ______ Ka value?
smaller
What is the correct formula for the conjugate acid of CH3NH2?
CH3NH3+
What is the cause of the inductive effect?
the difference of EN of the atoms involved
In an acid-base reaction, the equilibrium always favors the formation of what species?
weak acids and weak bases
Acid strength is ______ by any factor that makes the conjugate base more stable.
increased
What is an an electrophile?
an electron-deficient species
What is a nucleophile?
an electron-rich species
What is TsOH and what is it’s pKa?
p-toluenesulfonic acid, strong organic acid with pKa of -7
What are the three common types of bases?
negative charged oxygen bases (-OH + derivatives)
negative charge nitrogen bases (-NH2 + derivatives)
hydrife (H-)
What are pKa values of strong bases?
pKa > 12
Do all strong bases have a negative charge?
Yes, but not all species with a negative charge are strong bases.
What is a carbanion?
negatively charged carbon atom
What is a Lewis acid?
electron pair acceptor
What is a Lewis base?
electron pair donor
What must a Lewis base have?
available electron pair or pi bonds
T/F: All BL acids are Lewis acids?
True, but not all Lewis acids are BL acids
How many bonds are broken and formed in a Lewis reaction?
one formed, none broken (forms lewis acid-base complex)
