Chapter_16_stu_10th_ed_07

Chapter_16_stu_10th_ed_07 - Lets take a closer look at...

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Lets take a closer look at acids and bases. There many definitions of acids and bases Oldest definition - Arrhenius Acid - a substance that yield H 3 O 1+ in water - HCl HBr HC 2 H 3 O 2 Base - a substance that yields OH 1- in water - NaOH Ca(OH) 2 NH 3
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More general acid -base theory is the Bronsted-Lowry (Bronsted) acid base theory: Acid - a H 1+ (proton) donor Base - a H 1+ (proton) acceptor H Br + H 2 O -----> H 3 O 1+ + Br 1- (acid) (base) Donates H 1+ Accepts the H 1+
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H Br + H 2 O -----> H OH 2 1+ + Br 1- (acid) (base) H H -Br + H-O-H -----> H - O - H 1+ + Br 1- H 3 O 1+ + Br 1- ----> H 2 O + H Br (acid) (base) (base) (acid) acid 1 + base 2 base 1 acid 2 Conjugate Acid - Base Pairs - two substances that differ by a proton (H 1+ ) acid = HBr conjugate base = Br 1- base = Br 1- conjugate acid = HBr acid = H 3 O 1+ conjugate base = H 2 O base = H 2 O conjugate acid = H 3 O 1+
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NH 3 + H 2 O NH 4 1+ + OH 1- base 1 acid 2 acid 1 base 2 Conjugate acid base pairs base NH 3 conjugate acid = NH 4 1+ acid NH 4 1+ conjugate base = NH 3 acid H 2 O conjugate base = OH 1- 1-
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Amphoteric Substances -- substances that can act as either an acid or a base. Examples: H 2 O acid: H 2 O conjugate base OH 1- base : H 2 O conjugate acid H 3 O 1+ H 2 O + H 2 O H 3 O 1+ + OH 1- Bronsted - Lowry Acid-Base Reaction Acid + Base -----> Conjugate base + Conjugate acid
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Consider liquid ammonia NH 3 (l) + NH 3 (l) NH 4 1+ + NH 2 1- (amide) also partially neutralized polyprotic acids example: HSO 4 1- ion HSO 4 1- + OH 1- ----> SO 4 2- + H 2 O acid HSO 4 1- + H 3 O 1+ ----> H 2 SO 4 + H 2 O base acid: NH 3 conjugate base: NH 2 1- base: NH 3 conjugate acid: NH 4 1+
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Relative strengths of acids and bases - acid strength - desire to give up a proton strong acid wants to lose a proton readily weak acid wants to hold on to its proton base strength - desire to gain a proton strong base wants a proton badly weak base doesn’t really want to gain a proton strong acid - weak conjugate base weak acid - strong conjugate base
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Bronsted Acid- Base reaction a tug of war for a proton - will be won by the stronger acid and the stronger base i.e. the stronger acid-base pair with the weaker conjugate base and conjugate acid. stronger acid - donates a proton stronger base - gets a proton weaker acid - retains proton weaker base - does not get a proton HCl + H 2 O ----------> H 3 O 1+ + Cl 1- (rxn goes to completion) HCl is stronger acid than H 3 O 1+ H 2 O is a stronger base than Cl 1-
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Lets take a closer look at water. It is a weak electrolyte that dissociates slightly according to the equation H 2 O(l) H 1+ (aq) + OH 1- (aq) [H 1+ ][OH 1- ] K = ------------------ [H 2 O] K w = [H 1+ ][OH 1- ] = 1.0x10 -14 at 25°C KNOW K[H 2 O] = K w
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Lets take a closer look at the H 1+ ion. Consists of a proton with no
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This note was uploaded on 04/03/2008 for the course CHEM 114 taught by Professor Martin during the Spring '08 term at Moravian.

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Chapter_16_stu_10th_ed_07 - Lets take a closer look at...

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