In solution HCl a strong acid dissociates 100 acetic acid CH 3 COOH a weak acid

In solution hcl a strong acid dissociates 100 acetic

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In solution, HCl, a strong acid , dissociates 100% acetic acid (CH 3 COOH), a weak acid , is mostly molecules and only a few ions
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Strong acids have weak conjugate bases Make up only a few of the acids Strong Acids
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Weak acids make up most of the acids have strong conjugate bases Weak Acids
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Strong Bases Strong bases are formed from metals of Groups 1A(1) and 2A(2) include LiOH, NaOH, KOH, and Ca(OH) 2 dissociate completely in water KOH ( s ) K + ( aq ) + OH ( aq )
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Weak Bases Weak bases are most other bases dissociate only slightly in water form only a few ions in water NH 3( g ) + H 2 O ( l ) NH 4 + ( aq ) + OH ( aq )
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Water is Amphoteric Notice that H 2 O can act as a base (accepting H + from an acid) or as an acid (donating H + to a base like NH 3 ). H 2 O is amphoteric , a substance that can act as either an acid or a base. Other examples are bisulfate, HSO 4 - and HCO 3 -
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In the ionization of water , H + is transferred from one H 2 O molecule to another one water molecule acts as an acid, while another acts as a base H 2 O + H 2 O H 3 O + + OH Ionization of Water
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Pure Water is Neutral In pure water , the ionization of water molecules produces small but equal quantities of H 3 O + and OH ions molar concentrations are indicated in brackets as [H 3 O + ] and [OH ] [H 3 O + ] = 1.0 x 10 −7 M [OH ] = 1.0 x 10 −7 M
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Acidic Solutions Adding an acid to pure water increases the [H 3 O + ] causes the [H 3 O + ] to exceed 1.0 x 10 −7 M decreases the [OH ]
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Basic Solutions Adding a base to pure water, increases the [OH ] causes the [OH ] to exceed 1.0 x 10 −7 M decreases the [H 3 O + ]
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Comparison of [H 3 O + ] and [OH ]
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The ion product constant , K w , for water is the product of the concentrations of the hydronium and hydroxide ions K w = [ H 3 O + ][ OH ] is obtained from the concentrations in pure water K w = [ H 3 O + ][ OH ] K w = (1.0 x 10 −7 M()1.0 x 10 −7 M) = 1.0 x 10 −14 M 2 Ion Product of Water, K w
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[H 3 O + ] and [OH ] in Solutions In neutral, acidic, or basic solutions, the K w at 25 C is always 1.0 x 10 −14 M 2
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Guide to Calculating [H 3 O + ]
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Example of Calculating [H 3 O + ] What is the [H 3 O + ] of a solution if [OH ] is 5.0 x 10 −8 M? STEP 1 Write the K w for water: K w = [H 3 O + ][OH ] = 1.0 x 10 −14 M 2 STEP 2 Rearrange the K w expression to solve for [H 3 O + ]: [H 3 O + ] = 1.0 x 10 14 M 2 [OH ]
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Example of Calculating [H 3 O + ] STEP 3 Substitute the known [OH ] and calculate: [H 3 O + ] = 1.0 x 10 14 M 2 = 2.0 x 10 −7 M 5.0 x 10 −8 M
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Sample Problem Calculate the [H 3 O + ] concentration of a solution that has [OH - ] = 1.5 x 10 -2 M at 25 °C. Is the solution acidic or basic?
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pH Scale The pH of a solution is used to indicate the acidity of a solution has values that usually range from 0 to 14 is acidic when the values are less than 7 is neutral with a pH of 7 is basic when the values are greater than 7
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Testing the pH of Solutions The pH of solutions can be determined using a pH meter pH paper indicators that have specific colors at different pH values
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Mathematically, pH is the negative log of the hydronium ion concentration: pH = −log [H 3 O + ] For a solution with [H 3 O + ] = 1 x 10 −4 M pH = −log [1 x 10 −4 ] pH = -[-4.0] pH = 4.0 Calculating pH
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