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Chapter 10 Acids ( 酸 ) and Bases (碱). 10.1 Acids donate protons, bases accept them Sulfuric acid is the number one manufactured chemical, 85 billion pounds.

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Presentation on theme: "Chapter 10 Acids ( 酸 ) and Bases (碱). 10.1 Acids donate protons, bases accept them Sulfuric acid is the number one manufactured chemical, 85 billion pounds."— Presentation transcript:

1 Chapter 10 Acids ( 酸 ) and Bases (碱)

2 10.1 Acids donate protons, bases accept them Sulfuric acid is the number one manufactured chemical, 85 billion pounds (40,000,000 tons) annually in US. Acid has “sour” taste. Bases have “bitter” taste and slippery feel. In US, 25 billion pounds (10,000,000 tons) of NaOH was manufactured. Examples of acides

3 By definition, acids are chemicals that donate hydrogen ions, and bases are chemicals that accept them. HCl + H 2 O Cl- +H 3 O + (hydronium ion) H + donorH + acceptor (acid)(base) H 2 O+NH 3 OH - +NH 4 + H + donorH + acceptorH + acceptorH + donor (acid)(base)(base)(acid)

4 A salt is the product of an acid- base reaction (neutralization 中和 ) Acid Base Salt Water HCN + NaOH NaCN + H 2 O Hydrogen Sodium Sodium Cyanide Hydroxide Cyanide HNO 3 + KOH KNO 3 + H 2 O Nitric Potassium Potassium acid Hydroxide nitrate 2HCl + Ca(OH) 2 CaCl 2 + 2H 2 O Hydrogen Calcium Calcium Chloride Hydroxide chloride HF + NaOH NaF + H 2 O Hydrogen Sodium Sodium fluoride Hydroxide fluoride Table10.1 acid-base reactions and the salts formed

5 10.2 Some acids and bases are stronger than others The stronger an acid, the more readily it donates hydrogen ions. The stronger a base, the more readily it accepts hydrogen ions.

6 A nonelectrolyte B strong electrolyte C weak electrolyte (a)The pure water in this circuit is unable to conduct electricity because it contains practically no ions (b)Because HCl is a strong acid, nearly all of its molecules break apart in water, giving a high concentration of ions (c)Acetic acid, C 2 H 4 O 2, is a weak acid and in water only a small portion of its molecules break up into ions

7 10.3 Solutions can be acidic, basic or neutral In water, equal amount of H 3 O + and OH - (10 -7 M) (neutral solution) In acidic solution, more H 3 O + than OH - In basic solution, more OH - than H 3 O +

8 Acidity 酸性 (and basicity 碱性 ) can be scaled by pH value pH = -log[H 3 O + ]

9 10.4 Rainwater is acidic and ocean water is basic The main sources of acidic rainwater are CO 2 and SO 2. The damage of acidic rainwater depends on the local geology. 1. rain is acidified as it falls through the air 2. acid enters lake from rain 3. hydronium ions are neutralized by calcium carbonate released from limestone 2H 3 O + +CaCO 3 3H 2 O+CO 2 +Ca 2+ 1.Rain is acidified as it falls through the air 2. acid enters lake from rain 3. hydronium ions concentration increases, with potential harm to the ecosystem

10 Ocean can absorb CO 2 Carbon dioxide is absorbed and released Carbon dioxide is absorbed Fresh-water lake PH<7 Ocean PH=8.2

11 The concentration of CO 2 in air has been increased, which is related to global warming Fig10.18 Researchers at the Mauna Loa Weather Observatory in Hawaii have recorded increasing concentrations of atmospheric carbon dioxide since they began to collecting data in the 1950s.The chart left shows how the concentration of CO 2 in the atmosphere has changed in the last 40 years

12 10.5 Buffer solutions ( 缓冲溶液 ) resist changes in pH Effective buffer solutions can be prepared by mixing a weak acid with a salt of the weak acid. Fig10.19 Hydrochloric acid added to a solution containing acetic acid and sodium acetate is neutralized by the sodium acetate to form Additional acetic acid Fig Sodium hydroxide added to a Solution containing acetic acid and sodium Acetate is neutralized by the acetic acid To form additional sodium acetate


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