Acids and bases Flashcards
What was Arrhenius definition of acid and base
An Arrhenius acid is a substance which, when dissolved in water, produces hydrogen ion (H + (aq) )
a substance which when dissolved in water, gives off the OH - (aq) (hydroxide ion).
the major difference between this and the Bronstead lowry system is
1. You always have a BL acid and BL base in a reaction.
2. You don’t need H 2 O present.
Why do we not use ka and kb for strong acids/bases
Dissociation constants are used to give a
quantitative measure of the extent of ionization
of an acid or base reaction that is in equilibrium.
With strong acids and bases we assume full
dissociation, so there is no equilibrium and the
concept of an acid or base dissociation constant
is not applicable. The H+ concentration and pH
of their solutions can be derived directly from
their concentration.
True or false “Even compounds which contain no H + can be Arrhenius acids if they dissolve and react in H 2 O to
give H + .”
True
therefore as long as the molecule produces H+ with water it is an arrenhius acid no matter what
What was bonstead lowry definiton of acid and base
what about Lewis
and finally what are the two differences between B-L and Arrhenius
A: donates proton
B:accepts proton
Acid; accepts electron pair
Base : dontates electron pair
The two major differences between BL and Arrhenius is
1. You always have a BL acid and BL base in a reaction.
2. You don’t need H 2 O present.
amphoteric.
act as an acid or base ex ) water
H2O + H2O -> H30 + H+
so we know that there are lewis acids and bases, what is lewis neutralization?
Lewis Neutralization: formation of a coordinate bond between base and acid.
what are the two ways to find either acid or base concentration if you have one of the concentrations
use the ph method
or
use the water constant as you know kw=[OH][H]
therefore for example [H] = kw/[OH]
What is the Ka of a strong acid
ka >10^4
how much do medium acids dissociates and what is the ka
they dissociate 50:50 and the ka is 10^-3 <ka<10^3
remember
If pOH <7 this is a base so we discuss its [OH - ]
If pOH >7 this is an acid so we discuss its [H + ]
weak acids ka
ka < 10^-3
easy way to tell if strong base
weak bases are
if it has OH and it is group 2 or group 1 metal
Al(OH) 3 , NH 3 , and organic amines.
Key Trends from Hydro acids notes
The more electronegative the non-metal the______________
HF > HCL > HBR> HI but this is partially wrong because
as we go down a group, the strength of an acid _________, even though the central atom is
less electronegative.
but when we are comparing the strengths of acids on the same period than we use electronegativity as the deciding factor of acid strength
the easier the H+ leaves
Therefore the true ranking by strength is
HI>HBr>HCl>HF because even though the strong acid HF is more electro negative, it is the smallest atom out of the 4
However, as we go down a group, the strength of an acid _________, even though the central atom is
less electronegative.
Periodic trends for acids and bases notes
1)explain the periodic trends for the strength of bases on the periodic table
Rank the strong acids HClO4, H2So4, and H3PO4 using your peridot table
1) For Bases the further to left and lower on the chart the central atom M is, the more electropositive, the stronger the base!
2) Cl>S>P as Cl is more electro neg than others on same period
