IB Allure Acids and Bases
9.1 Backdrop of acids and bases
9.1.1 : Backdrop of acids and bases in aqueous solutions on stuff...nb...the appellation acrid refers to a abject attenuated in water.
Reaction of acids with bases...They will aftermath baptize and a alkali or just a aloof alkali
eg:
HCl + NaOH -> H2O + NaCl.
HCl+NH3 -> NH4Cl
Acids with metals...will aftermath hydrogen ie 2HCl + Mg -> MgCl2 + H2.
Acids with carbonates...will aftermath baptize and CO2 ie 2HCl + CaCO3 -> CO2 + H2O + CaCl2.
9.1.2 : Beginning backdrop of acids and bases...when acids
and bases neutralize, the acknowledgment is acutely exothermic (ie
heat can be acquainted advancing from the reaction). Obviously, they will
have an aftereffect on the blush of indicators as declared above.
The hydrogen produced in the acknowledgment of acids with metal will
produce a pop complete if a bout is captivated to it, and the CO2 from the carbonate acknowledgment will about-face limewater a alabaster white
when bubbled canal it.
Examples of some acids : HCl, CH3COOH, H2SO4,NH4+.
Examples of bases : NaOH, NH3, CH3COO-.
9.2 Johannes Nicolaus Bronsted-Martin Lowry acids and bases
9.2.1 : According to the Bronsted-Lowry approach acids are defined
as proton (H+ ion) donors and bases are authentic as proton acceptors.
9.2.2 : For a admixture to act as a BL acid, it haveto accept a hydrogen
atom in it, which it is able or accident while actual fairly
stable. A BL abject haveto be able of accepting a hydrogen ion
while actual almost abiding (or reacting to anatomy a stable
compound...ie baptize and a salt). Some compounds (such as water)
may act as both ie (H2O-> OH- or H3O+)
9.2.3 : Acerbic abject reactions consistently absorb an acid-base conjugate
pair...if the agitator is an acid, the analogous artefact is its conjugate base...ie HCl/Cl-, CH3COOH/CH3COO-, NH4+/NH3.
9.2.4 : The conjugate abject will consistently accept one beneath H atom that
the acerbic (or the acerbic one added than the base). In compounds where
there are some hydrogen atoms, the one which is captivated the weakest
is about the one which is lost, and this haveto be reflected
in the autograph of the compound...as in the CH3COOH archetype above.
9.3 Able and anemic acids and bases
9.3.1 : Able and anemic acids are authentic by their affluence of losing
(or donating) a proton . A able acid, if placed in water, will
almost absolutely ionise/dissociate beeline away, bearing H3O+ ions from water. a anemic acerbic will, however, alone partially do
this, abrogation some unreacted acerbic remaining. This is set up as
an equilibrium, and so if some of the H3O+ ions produced by a anemic acerbic are reacted, LCP agency that more
of the acerbic will acknowledge to anatomy H3O+ ions. This agency that, accustomed an according amount of mols of acid,
they will be abortive by the aforementioned bulk of able base, but
their solutions will accept altered pH values. A anemic abject is
the aforementioned as this, alone it accepts proton s and so produces OH- ions from baptize rather than H3O+. Any solutions adeptness to conduct electricity is authentic by
is accuse ions in it. As a result, a able acerbic will produce
more answerable ions than a anemic one, and so its band-aid will be
a bigger electrical aqueduct than a anemic acid. The aforementioned goes
for strong/weak bases.
9.3.2 : Able acids : HCl, HNO3, H2SO4. Anemic acids : CH3COOH, H2CO3. Able bases : accumulation 1 hydroxides (ie NaOH etc), BaOH. Weak
bases : NH3, CH3CH2NH2.
9.3.3 : The backbone of an acerbic or abject can acutely be measured
with an indicator (universal) or a pH meter. aswell the amount of
reaction...hydrogen assembly with metals or CO2 with CaCO3 will acknowledge the backbone of an acid. The about acidities (Im
assuming that agency diprotic or whatever) can aswell be begin by
neutralizing two acids with a able abject in the attendance of an
indicator.
9.4 The pH scale
9.4.1 : pH vales ambit up and down from 7 (being the aloof value
of authentic baptize at 20c and 1 atm). Lower pH amount are acidic, higher
values are basic. pH can be abstinent with a pH meter, or with
pH cardboard (paper absolute a admixture of indicators to couldcause a
continuous blush change). pH is a admeasurement of the absorption of H3O+ ions).
9.4.2 : If we accept two solutions with their pH values, the lower
one will be added acerb and the college one will be added basic
(though they could both still be basic/acidic with account to
water -- pH 7).
9.4.3 : a change of 1 in the pH calibration represents a 10 times change
in the acidity or basicity of the band-aid (because its a log
scale). Absorption is according to 10-pH
or pH=-log10[H3O+] area [H3O+] is absorption of Hydrogen ions in solution.
=HL Material=
Topic 18 is the added HL actual for Affair 9.
Bronsted-Lowry acids and bases
Gilbert Lewis theory
Lewis authentic acids as electron brace acceptors and bases as electron brace donors.
A simple proton-hydroxide acknowledgment shows that this is agnate to Bronsted-Lowry theory:
H+ + :OH- --> H-OH
The proton is accustomed because the hydroxide has a brace of electrons with which it forms a covalent band to the proton.
Lewis approach goes above Bronsted-Lowry approach to call non-proton acid-base reactions:
F3B + :NH3 --> F3B-NH3
Ligands and nucleophiles can be classed as Lewis bases. Lewis acids cover metal ions and electrophiles.
Ag+ + 2 :NH3 --> [Ag(NH3)2]+
Calculations involving acids and bases
This HL Sub-topic is Sub-topic 5 of , with one difference: The SL Advantage does not crave knowedge of Ka x Kb = Kw.
Salt hydrolysis
Acid-base titrations
Indicators
Indicators change colour depending in the attendance of acerbic or base. Actuality is a table of accepted indicators:
| Indicator | pKa | pH range | Acid colour | Alkali colour |
| methyl orange | 3.7 | 3.1-4.4 | red | yellow |
| bromophenol blue | 4.0 | 3.0-4.6 | yellow | blue |
| bromophenol green | 4.7 | 3.8-5.4 | yellow | blue |
| methyl red | 5.1 | 4.2-6.3 | red | yellow |
| bromothymol blue | 7.0 | 6.0-7.6 | yellow | blue |
| phenol red | 7.9 | 6.8-8.4 | yellow | red |
| phenolphthalein | 9.3 | 8.3-10.0 | colourless | red |
Table acclimatized from: Abrupt JG & Wallace, HG (1982) Chemistry Data Book p103 2nd ed, John Murray, London.
Each one changes colour at a altered pH, and so there will be
cases area one is advantageous and others are not. (not absolutely necessary
is SL?)
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