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Published byColleen Harper Modified over 9 years ago
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Acids and Bases
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Ionization of Water Only happens to a small amount of water molecules H 2 O separates into ______________ Not the whole story H+ never occurs on its own In reality, another H 2 O molecule picks it up and becomes ___________________
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Acids and Bases AcidsBases Taste sourTaste bitter Feel wateryFeel slippery Conduct electricity Change litmus to redChange litmus to blue pH = 0-7pH = 7-14 Neutralize basesNeutralize 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 H 2 SO 4 Base - ________________ For example: NH 3 and OH -
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Conjugate Acid and Bases Occur on the other side of acid base equations. Lets look again at NH 3 is a ________. It will accept a proton (H + ) H 2 O is an _______. It will donate a proton (H + ) NH 4 + is NH 3 ’s _____________. It can donate a proton (H + ) to become NH 3 again OH - is water’s ______________. It can accept a proton (H + ) to become H 2 O again
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Amphiprotic Amphiprotic – Substances that can act like an acid or a base Water is an amphiprotic substance. H 2 O can accept a proton to become H 3 O + H 2 O 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 ______ H 2 SO 4 H 2 SO 4 gives up 1 H + to form HSO 4 - This happens to ______ of the molecules since H 2 SO 4 is strong HSO 4 - gives up another H + to form SO 4 -2 This only happens to some HSO 4 - because it is _______ Solution will contain _________ of water molecules H 3 O + molecules (mostly from the first H+ but some from the second and from ionization of water) HSO 4 - a little bit of SO 4 -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: H 2 SO 4 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 2H 2 O(l) H 3 O + (aq) + OH - (aq) This equilibrium ___________________ In other words, there is far more water molecules than hydronium and hydroxide ions in a sample K w = ________________ K w = 1.0 x 10 -14 In pure water and neutral solutions, [H 3 O + ] 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 V a M a = V b M b V a = volume in L of acid M a = molarity of acid V b = volume in L of base M b = molarity of base
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