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Acids and Bases. Arrhenius Theory Acids produce H + ions. Acids produce H + ions. Bases produce OH - ions. Bases produce OH - ions. HCl  H + + Cl - NaOH.

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Presentation on theme: "Acids and Bases. Arrhenius Theory Acids produce H + ions. Acids produce H + ions. Bases produce OH - ions. Bases produce OH - ions. HCl  H + + Cl - NaOH."— Presentation transcript:

1 Acids and Bases

2 Arrhenius Theory Acids produce H + ions. Acids produce H + ions. Bases produce OH - ions. Bases produce OH - ions. HCl  H + + Cl - NaOH  Na + + OH - NaOH  Na + + OH -

3 Strong acids HCl (stomach acid) H 2 SO 4 (battery acid) HNO 3 (nitric acid) Weak acids H 2 CO 3 (carbonic acid) HC 2 H 3 O 2 (acetic acid)

4 Strong bases KOHNaOH Weak bases NH 4 OH Mg(OH) 2 (milk of magnesia)

5 Bronsted-Lowry Theory Acids donate protons Acids donate protons Bases accepts protons Bases accepts protons NH 3(g) + H 2 O(l)  NH 4 + (aq) + OH - (aq) NH 3(g) + H 2 O(l)  NH 4 + (aq) + OH - (aq) baseacid conjugate acid conjugate base

6 Conjugate acids and bases A conjugate acid is formed when a base gains an H + ion. A conjugate acid is formed when a base gains an H + ion. A conjugate base is formed when an acid loses an H + ion. A conjugate base is formed when an acid loses an H + ion. HCl(g) + H 2 O(l)  H 3 O + (aq) + Cl - (aq) HCl(g) + H 2 O(l)  H 3 O + (aq) + Cl - (aq) acid base acid base H 3 O + (aq) + Cl - (aq)  HCl(g) + H 2 O(l) H 3 O + (aq) + Cl - (aq)  HCl(g) + H 2 O(l) acid base acid base Acid + base  conjugate base + conjugate acid conjugate acid conjugate base conjugate acid

7 Acidconjugate base HClCl - H 2 SO 4 HSO 4 - H 3 O + H 2 O Baseconjugate acid NH 3 NH 4 + H 2 OH 3 O +

8 Monoprotic- has 1 H; HCl Monoprotic- has 1 H; HCl Diprotic- has two H; H 2 SO 4 Diprotic- has two H; H 2 SO 4 Triprotic- has three H; H 3 PO 4 Triprotic- has three H; H 3 PO 4

9 Characteristics of acids Taste sour Taste sour pH from pH from Has H + at the beginning of the formula Has H + at the beginning of the formula Produce H 2  when reacting with most metals Produce H 2  when reacting with most metals Neutralize bases Neutralize bases Conducts electricity (electrolytes) Conducts electricity (electrolytes) Turns litmus paper red Turns litmus paper red

10 Characteristics of bases Taste bitter Taste bitter pH between pH between Have OH - ion Have OH - ion Feels slippery Feels slippery Neutralize acids Neutralize acids Turns litmus paper blue Turns litmus paper blue

11 Naming acids anion acid nameexample -ide Hydro- icHCl hydrochloric acid -ite -ousHNO 2 nitrous acid -ate -icHNO 3 nitric acid

12 Try these H 2 SO 4 H 2 SO 4 HF HF H 3 PO 4 H 3 PO 4 H 2 SO 3 H 2 SO 3 sulfuric acid hydrofluoric acid phosphoric acid sulfurous acid

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14 pH scale 1  7  14 acid neutral base

15 Ionization of water H 2 O(l)  H + (aq) + OH - (aq) H 2 O(l)  H + (aq) + OH - (aq)

16 [H + ] means hydrogen ion concentration in moles per liter (molarity). Water at 25 ◦ C : [H + ] = moles/L [OH - ] = moles/L [OH - ] = moles/L Since [H + ] = [OH - ], water is neutral

17 [H + ] ∙ [OH - ] = mole 2 /L 2 Example: Find the [OH - ] in a solution in which [H + ] = [H + ] ∙ [OH - ] = mole 2 /L 2 [H + ] ∙ [OH - ] = mole 2 /L 2 [OH - ] = [OH - ] = 10 -9

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19 [H + ] = 10 -pH [OH - ] = 10 -pOH pH + pOH = 14.0 Sample problem: A 0.01 M sample of NaOH completely ionizes. What is its pH, pOH, [H + ], and [OH - ] ? [OH - ] = 0.01 mole/L = pOH = 2 pH = 14 – pOH = 12 [H + ] =

20 Sample Problem 2: A solution has a pH of 3. What is its pOH, [H + ], and [OH - ]? pOH = 14 – 3 = 11 [OH - ] = [H + ] = =

21 pH values of common liquids Human gastric juices 1-3 Lemon juice Vinegar Soda 2-4 O.J. 3-4 Coffee, black 4 Milk 6.5 Blood Sea water Ammonia M NaOH 14.0

22 Neutralization reactions Always form a salt and water Always form a salt and water Salt- a crystalline compound formed from an acid’s anion and a base’s cation. Salt- a crystalline compound formed from an acid’s anion and a base’s cation.

23 Titration An unknown concentration of acid or base can be determined by measuring the amount of a known acid or base that will neutralize the other. An unknown concentration of acid or base can be determined by measuring the amount of a known acid or base that will neutralize the other. An indicator changes color when the “endpoint”, or neutralization occurs. An indicator changes color when the “endpoint”, or neutralization occurs.

24 Titration Standard solution- one whose concentration is known Standard solution- one whose concentration is known Endpoint- the point at which equivalent amounts of reactants are present. Endpoint- the point at which equivalent amounts of reactants are present. M∙V = moles M∙V = moles M a V a =M b V b M a V a =M b V b

25 If 15.0ml of 0.500M NaOH is used to neutralize 25.0ml HCl, what is the concentration of the acid? If 15.0ml of 0.500M NaOH is used to neutralize 25.0ml HCl, what is the concentration of the acid? NaOH + HCl  H 2 O + NaCl NaOH + HCl  H 2 O + NaCl 15mL x 0.500M = 25.0 ml x M a 15mL x 0.500M = 25.0 ml x M a = 0.300M HCl = 0.300M HCl

26 Buffers Can absorb acids and bases without changing its pH Can absorb acids and bases without changing its pH A weak acid (HA) with its salt (NaA) A weak acid (HA) with its salt (NaA) A weak base (MOH) with its salt (MA) A weak base (MOH) with its salt (MA)

27 HF(aq)  H + (aq) + F - (aq) Buffered solution is mostly HF and F -. If H + is added: H + + F -  HF If OH - is added: OH - + HF  F - + H 2 O


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