Acid and Base. 16.1 Acids and Bases Arrhenius acid produces H + in aqeuous solution Arrhenius base...
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Transcript of Acid and Base. 16.1 Acids and Bases Arrhenius acid produces H + in aqeuous solution Arrhenius base...
Acid and Base
16.1 Acids and BasesArrhenius acid produces H+ in aqeuous
solutionArrhenius base produces –OH in aqueous
solutionE.g
Strong acidHCl(g) H+(aq) + Cl-(aq) Strong base
NaOH(s) Na+(aq) + -OH(aq)
16.1 Acids and BasesBonsted-Lowry acids: proton (H+) donorBronsted_Lowry bases: proton (H+) acceptorConjugated acids: new acid that resulted
from accepting H+
Conjugated bases: new base that resulted from losing H+
E.g HA(aq) + H2O(l) H3O+(aq) + A-(aq)
HCl(aq) + H2O (l) H3O(aq) + Cl-(aq)
Examples Which of the following represent conjugate
acid-base pairs?
a. HF, F- b. NH4+, NH3
c. HCl, H2O d. HClO4, ClO4-
Write the following base for each of the following
a. HClO2 b. H2SO3 c. NH3
16.2 Acid StrengthStrong acids:
completely ionized or completely dissociated
Forward reaction is predominated Most of HA is
dissociatedConjugated base is
weak and has low attraction for proton
HA(aq) + H2O(l) H3O+(aq) + A-(aq)
Acids StrengthWeak acids: partially ionized or dissolved Reverse reactions is predominated
Most of HA is undissociateConjugated base is strong and has high attraction for
protonHC2H3O4(aq) + H2O(l) H3O+(aq) +C2H3O4
-(aq)
AcidsDiprotic acids: acids that can furnish two
protons H2SO4(aq) H+(aq) + HSO4
-(aq)
HSO4-(aq) H+(aq) + SO4
2- (aq0Oxyacids: acidic hydrogen is attached to
an oxygen Organic acids: those with a carbon-atom
backbone
16.3 Water as an Acid and a BaseAmphoteric substance: substance that
can behave as an acid or as a baseH2O(l) + H2O (l) H3O+ (aq) + -OH(aq)
At 25oC[H3O+]= [-OH] = 1.0 x 10-7 M
Kw = [H3O+] x [-OH] = 1.0 x 10-14
Kw = ion-product constant of water
Water as an acid and as a base[H3O+] = [-OH] neutral solution
[H3O+] > [-OH] acidic solution
[H3O+] < [-OH] basic solution
ExamplesCalculate [H3O+] or [-OH] as required for
each of the following solution at 25oC and state whether the solution is neutral, acidic, or basic.1.0 x 10-5 M –OH3.4 x 10-4 M H3O+
2.0 x 10-2 M –OH10.0 M H3O+
Using Ion-Product Constant in CalculationsIs it possible for an aqueous solution at 25oC
to have [H3O+] = 0.010 M and [-OH] = 0.010 M?
Which is greater, [-OH] or [H3O+], if [H3O+] = 2.8 x 10-5M in an aqueous solution at 25oC?
16.4 The pH scalepH scale provides a
compact way to represent solution acidity
Express the common logarithm (base 10 log)
pH = - log [H3O+] scale : 1.00 to 14.00Smaller pH => more
acidic
The pOH scalesRepresents solution basicitypOH = - log [-OH]Scale from 1.00 to 14.00Smaller pOH => more basic
ExamplesCalculate the pH value for each of the
following solution at 25oC
A solution in which [H3O+] = 1.0 x10-9M
A solution in which [-OH] = 5.0 x 10-5 M
ExamplesCalculate the pH and pOH for each of the
following solutions at 25oC1.0 x 10-3 M –OH3.6 x 10-9 M H3O+
Calculate pH from pOHpH + pOH = 14.00
The pH of blood is about 7.4 What is the pOH of blood?
A sample of rain in an area with severve air pollution has a pH of 3.5. What is the pOH of this rain water
Calculating [H3O+] from pHRecall pH = -log [H3O+]
Inverse log (-pH) = inverse log (log[H3O+])
inverse log (-pH) = [H3O+]
10-pH = [H3O+]
E.G Convert pH = 7.0 to [H3O+]
*Similar calculation is applied to pOH10-pOH = [-OH]
ExamplesThe pH of a human blood sample was
measured to bee 7.41. What is the [H3O+] in this blood?
The pH of rainwater in a polluted area was found to be 3.50. What is the [H3O+]?
The pOH of water in a fish tank is found to be 6.59. What is the [-OH]?
The pOH of a liquid drain cleaner was found to be 10.50 What is the [-OH] for this cleaner?
16.5 Calculating the pH of strong Acid SolutionRecall that strong acids are completely
ionized when dissolved in waterE.g HCl(aq) H+(aq) + Cl-(aq) 0.10 M 0.10M 0.10M
Calculating pH of Strong Acid SolutionsCalculate the pH of 0.10 HNO3
Calculate the pH of a 1.2 x 10-6 HBr
16.6 Buffer SolutionBuffer solution is one that resists a change in
its pH even when a strong acid or base is added to it.
Buffer solution is made of a weak acid and its conjugated baseHA(aq) + H2O(l) H3O+(aq) + A-
Addition of H+ reacts with the base A-
Addition of –OH reacts with weak acid
ExamplesOur blood system is controlled by
H2CO3(aq) + H2O(l) HCO3-(aq) +
H3O+(aq)
Write the reaction equation forAddition of HCl
Addition of NaOH