Acids and Bases
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Transcript of Acids and Bases
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Acids and Bases
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Ionization of Water Only happens to a small amount of water
molecules H2O separates into ______________ Not the whole story
H+ never occurs on its own In reality, another H2O molecule picks it up and
becomes ___________________
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Acids and Bases
Acids Bases
Taste sour Taste bitter
Feel watery Feel slippery
Conduct electricity Conduct electricity
Change litmus to red Change litmus to blue
pH = 0-7 pH = 7-14
Neutralize bases Neutralize acids
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Classifying Acids and Bases Arrhenius
Acid- substance that dissociates into ______________ For Example: ___________________
Base- substance that dissociates into ______________ For example: __________________
Does not explain bases without an OH ion
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Classifying Acids and Bases (cont) Brønsted-Lowry
Acid - _______________ For example: HCl and H2SO4
Base - ________________ For example: NH3 and OH-
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Conjugate Acid and Bases Occur on the other side of acid base equations. Lets look again at
NH3 is a ________. It will accept a proton (H+) H2O is an _______. It will donate a proton (H+) NH4
+ is NH3’s _____________. It can donate a proton (H+) to become NH3 again
OH- is water’s ______________. It can accept a proton (H+) to become H2O again
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Amphiprotic Amphiprotic –
Substances that can act like an acid or a base Water is an amphiprotic substance.
H2O can accept a proton to become H3O+
H2O can donate a proton to become OH-
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Strength of Acids and Bases Depends on how much they dissociate in
water Strong
Considered to dissociate _____________ in water Weak
Only partially dissociate in water Reaction is _____________________
Conjugate pairs Strength is ______________________
For example: Strong acids have weak conjugate bases
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Acids Strong acids
________ ________ ________ ________ ________ ________ ________ All have 100% of the molecules
break apart. There is no reverse reaction.
Weak acids All others
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Polyprotic Acids Have multiple ______ H2SO4
H2SO4 gives up 1 H+ to form HSO4-
This happens to ______ of the molecules since H2SO4 is strong
HSO4- gives up another H+ to form SO4
-2
This only happens to some HSO4- because it is _______
Solution will contain _________ of water molecules H3O+ molecules (mostly from the first H+ but some from the
second and from ionization of water) HSO4
-
a little bit of SO4-2
A little bit of OH- (from the ionization of water)
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Acid Names Binary acids (______________)
Prefix __________ Root of element name Suffix ___________ Add acid For example: HCl is ___________________
Acids with Oxygen (_________________) Root name of polyatomic (with polyatomic prefix if applicable)
Some polyatomic roots are modified slightly to be easier to say Suffix
-ic with polyatomics ending in _______ -ous with polyatomics ending in _______
Add acid For example: H2SO4 is ______________
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Bases Strong bases
Group 1 metals with OH-
Ca, Sr, and Ba with OH-
These three are not very soluble in water, but the amount that does dissolve ionizes completely.
Weak bases All others
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Chemical Equilibrium Reversible reactions Indicated with a _________
Both reactions are happening at the same time System reaches equilibrium when both are happening at
same _____ At equilibrium
Could have lots of reactant and little product Could have lots of product and little reactant Could have equal amounts of both
Changes to the system can shift equilibrium Temperature Pressure Adding reactants or products
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Equilibrium Expressions Mathematical way to represent equilibrium For the equation, ________________________
K = [C]c [D]d
[A]a [B]b
K is the equilibrium constant for the equation [ ] indicates the concentration of each substance
in mol/L (M) _______________ are not entered into the expression
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Ionization of Water 2H2O(l) H3O+(aq) + OH-(aq)
This equilibrium ___________________ In other words, there is far more water molecules than
hydronium and hydroxide ions in a sample
Kw = ________________ Kw = 1.0 x 10-14
In pure water and neutral solutions, [H3O+] and [OH-] are 1.0 x 10-7 M
In acidic solutions, ____________________________ In basic solutions _____________________________
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pH pH
Stands for potential of Hydrogen (really hydronium)
______________ scale pH = -log [H+] or [H+] = 10-pH
Values between 0-14 with each number representing a 10-fold increase from the previous number pH 7 is ________ pH = 7 is ________ pH 7 is ________
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pOH pOH = -log [OH-] or [OH-] = 10-pOH
Opposite scale pOH 7 is ________ pOH = 7 is ________ pOH 7 is _________
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Indicators Compounds that change color in the presence
of different levels of pH
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Soil pH 6.0-6.5
Soil pH 5.0-5.5
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Neutralization (Acid-Base Reaction) Special type of double displacement reaction Acid + Base ___________________
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Titration Process of neutralizing an acid (or base) with an
unknown concentration with a base (or acid) of a known concentration
Moles of H3O+ must equal moles of OH- for neutralization to occur
Often indicators are used to determine the end of the reaction
VaMa = VbMb
Va = volume in L of acid Ma = molarity of acid Vb = volume in L of base Mb = molarity of base