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Acids & Bases Properties Acid-Base Theories Acid-Base Reactions.

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Presentation on theme: "Acids & Bases Properties Acid-Base Theories Acid-Base Reactions."— Presentation transcript:

1 Acids & Bases Properties Acid-Base Theories Acid-Base Reactions

2 Properties Both conduct electricity (electrolytes) because they break apart to some degree in water. Acids produce H + (proton) in water. Bases produce OH - (hydroxide) in water. Samples: Acids: vinegar(acetic acid), lactic acid in sour milk, citric acid, Bases: ammonia, lye (NaOH), Milk of Magnesia Mg(OH) 2.

3 More on Acids 1.Sour taste. NEVER taste acids in lab situations. 2.Change color of indicators. 3.Some acids react with metals & release H 2 gas. 4.Acids react with bases to produce salt & water. When neutralization occurs, #1.-#3 disappear. 5.Conduct electric current.

4 Neutralization Reaction Acid + Base --> Salt + Water HCl + NaOH --> NaCl + H 2 0 H 2 SO 4 + Ca(OH) 2 --> CaSO 4 + 2H 2 0

5 Acid Nomenclature Binary Acids contain Hydrogen and another element: Hydro + root of 2 nd element + ic – HFhydrofluoric acid – HClhydrochloric acid – HBrhdrobromic acid – HIhydroiodic … – H2Shydrosulfuric …

6 Oxyacids Contain H, O, and a 3 rd element. More are listed in your book.

7 Common Industrial Acids Sulfuric Nitric Phosphoric Hydrochloric Acetic

8 Bases Bitter taste (NEVER taste bases in labs). Change the color of indicators. Slippery feel (dilute bases, don’t touch concentrated bases) React with acids to produce salt & water Conduct electric current.

9 Arrhenius Acids & Bases Arrhenius Acid is a chemical compound that increases the concentration of hydrogen ions, H+, in aqueous solutions. Arrhenius Base is a chemical compound that increases the concentration of hydroxide ions, OH-, in aqueous solutions. When put with water, these compounds dissociate (break apart) forming ions

10 HNO 3 (l) + H 2 0 (l) --> NO 3 - (aq) + H (aq) When put in water, HNO 3, ionizes and the charged particles formed can conduct electricity. The amount of H (hydronium) produced is an indication of the acid’s strength.

11 Strong Acids ionize completely in water. Strong Acids: HI HClO 4 HBr HCl H 2 SO 4 HClO 3 Weak Acide release few hydrogen ions in water. Weak Acids: HSO 4 - H 3 PO 4 HF CH 3 COOH H 2 CO 3 H 2 S HCN HCO 3 -

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13 For Bases, the strength depends on how it dissociates (ionizes) Strong Bases ionize completely. Strong Bases Ca(OH) 2 --> Ca OH - Sr(OH) 2 Ba(OH) 2 NaOH KOH RbOH CsOH Weal Bases ionize slightly. Weak Bases NH 3 + H 2 O NH OH - C 6 H 5 NH 2 “ means the reaction is reversible

14 Assignment #72: 476/1-4 #75: 491/1,4-11

15 Acid-Base Theories Bronsted-Lowry Acids donate protons (H + ) Molecules or ions can donate protons. HCl + NH 3  NH Cl -

16 The HCl is a Bronsted-Lowry Acid. It donates a proton to water Water can act as a Bronsted-Lowry Acid also as in the following reaction: H2O (l) + NH3 OH- + NH4+

17 Bronsted-Lowry Bases accept protons. In the equation below, ammonia is the base, because it accepts the proton to become an ammonium ion. acid base HCl + NH 3  NH Cl -

18 Mono- and Polyprotic Acids Monoprotic acids can only donate one proton per molecule. Ex.: HCl, HNO 3 Polyprotic acids can donate 2 or more protons per molecule. Ex.: H 2 SO 4, H 3 PO 4 For polyprotic acids the donations occur in stages, losing one H + at a time.

19 Lewis Acids and Bases Arrhenius and Bronsted-Lowery definitions have some limitations. Lewis classification is based on bonding and structure including substances without hydrogen. The Lewis classification is more complete than the other 2 methods.

20 A Lewis acid is an atom, ion or molecule that accepts an electron pair to form a covalent bond. Dot notation Structural formula – a bar represents what? A pair of shared electrons.

21 A Lewis base is an atom, ion, or molecule that donates an electron pair to form a covalent.

22 Lewis Acid-Base Reaction is the formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor. Pair of donated electrons

23 Assignment: #73: 482/1,2 #76: 491/12-15,17,18 Samples are done on the next 2 frames.

24 491/15. Dilute HCl(aq) and KOH(aq) are mixed in chemically equivalent quantities. a)Write the formula equation for the reaction. HCl(aq) + KOH(aq) --> KCl(aq) + H 2 O(l) b)Write the overall ionic equation. H 3 O + (aq) + Cl - (aq) + K + (aq) + OH - (aq) --> K + (aq) + Cl - (aq) + 2H 2 0(l) c) Write the net ionic equation. H 3 O + (aq) + OH - (aq) --> 2H 2 0(l)

25 492/17a. Write the formula equation and net ionic equation for this reaction. Formula equation for: Zn(s) + HCl(aq) --> Zn(s) + 2HCl(aq) --> ZnCl 2 (aq) + H 2 (g) Overall ionic equation: Zn(s) + 2H 3 O + (aq) + 2Cl - (aq) --> Zn 2+ (aq) + 2Cl - (aq) + H 2 (g) + 2H 2 0(l) Net ionic equation: Zn(s) + 2H (aq) --> Zn 2+ (aq) + H 2 (g) + 2H 2 0(l)

26 Acid-Base Reactions Now we are going to use Bronsted-Lowry description to explore acid-base reactions. What was the Bronsted-Lowery theory? B-L acid donates protons B-L base accepts protons

27 A conjugate base is the species that remains after a Bronsted-Lowery acid has given up a proton. A conjugate acid is the species that forms when a Bronsted-Lowery base gains a proton.

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29 Acid-Base Reactions Now we are going to use Bronsted-Lowry definitions to study Acid-Base reactions. The species that remains after a Bronsted-Lowry acid has given up a proton is the conjugate base of that acid. HF + H 2 O F - + H Acid conjugate base

30 The species that is formed when a Bronsted- Lowry base gains a proton is the conjugate acid of that base. HF(aq) + H 2 O(l) F - (aq) + H (aq) Base conjugate acid

31 HF(aq) + H 2 O(l) F - (aq) + H (aq) Acid Base conjugate conjugate base acid acid 1 base 2 base 1 acid 2 Conjugate pairs: (1)HF and F - (2)H 2 0 and H 3 0 +

32 Strength of Conjugate Acids & Bases On Page 1 of your handout for this chapter, you have a table which lists and compares the strengths of various acids and their conjugate bases. Get your Ch. 14 handout out now.

33 Determining direction of equilibrium in Acid-Base reactions The stronger an acid is, the weaker its conjugate base will be. The stronger a base is, the weaker its conjugate acid will be. From these concepts, we can predict the outcome of a reaction.

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38 Assignment for this section: #74: 489/1,2 #77: 491/19-25 #78: 492/26-30,36,37 (Overall practice problems) Sample problem on next page:

39 492/23a: Identify the proton donor or acid and the proton acceptor or base. Label each acid- base conjugate pair. CH 3 COOH + H 2 0 H CH 3 COO - acid base conjugate conjugate acid base

40 Another sample. 492/29a. Write the formula equation, the overall ionic equation, and the net ionic equation for a neutralization reaction that would form RbClO 4. Formula equation: RbOH(aq) + HClO 4 (aq) --> RbClO 4 (aq) + H 2 0(l)

41 Overall Ionic equation: Rb + (aq) + OH - (aq) + H (aq) + ClO 4 - (aq) --> Rb + (aq) + ClO 4 - (aq) + 2H 2 0(l) Net ionic equation: H (aq) + OH - (aq) --> 2H 2 0(l)

42 Amphoteric Compounds These can act as either an acid or a base. Water acts as a base in this reaction: H 2 SO 4 (aq) + H 2 0(l) --> H (aq) + HSO 4 - (aq) acid 1 base 2 acid 2 base 1 But, water acts as an acid here: NH 3 (g) + H 2 0(l) NH 4 + (aq) + OH - (aq) Base 1 acid 2 acid 1 base 2

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44 Review AcidsBases Arrhenius concentration of: [H + ] [OH - ] Bronsted-Lowry H + donor H + acceptor Lewis, electron pair: acceptor donor


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