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ACIDS AND BASES UNIT 10 General Chemistry Spring 2010.

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Presentation on theme: "ACIDS AND BASES UNIT 10 General Chemistry Spring 2010."— Presentation transcript:

1 ACIDS AND BASES UNIT 10 General Chemistry Spring 2010

2 The Importance Of acids… Blood is controlled by buffers Citrus fruits (citric acid) Vinegar (acetic acid) Vitamin C (ascorbic acid) Aspirin (acetyl salicylic acid) Car batteries (sulfuric acid)

3 The Importance Of bases… Baking soda Milk of magnesia Antacids have carbonates, bicarbonates and hydroxides to neutralize acids Ammonia (cleaning products) Sodium hydroxide, aka: lye (oven and drain cleaner)

4 How do you know you have… An acid? Produces H + in water Blue litmus paper turns red Sour taste Reacts on metal pH less than 7 Metal etched using acid

5 How do you know you have… A base? Produces OH - ions in water (hydroxide ions) Red litmus paper turns blue Slippery feel Bitter taste (taste shampoo tomorrow morning) pH higher than 7

6 pH Means potency of hydrogen Refers to pondus hydrogenii (potential hydrogen)

7 The pH Scale

8 Arrhenius Acids Substance that ionizes in water to produce hydrogen ions (H + ) ionization- process by which covalent compounds form cations and anions Ex) HCl H + + Cl -

9 Arrhenius Base Substance that dissociates in water to release hydroxide ions (OH - ) dissociation- process by which ionic compounds separate into ions Ex) NaOH Na + + OH -

10 Neutralization Reactions An acid neutralizes a base to yield a salt and water. Example A) Hydrochloric acid reacts with sodium hydroxide to give the salt sodium chloride and water. HCl + NaOH NaCl + H 2 O Different acids yield different salts, but water is always a product

11 Neutralization Reactions Example B) H 2 SO 4 + 2 NaOH Na 2 SO 4 + 2 H 2 O The hydrogen ion (H + ) from the acid is neutralized by the hydroxide (OH - ) ion from the base. These two ions combine to form water.

12 Identifying an Acid and Base Each salt is composed of the cation (+) from the reacting base and the anion (-) from the acid. Predict the acid and base that produce the following salts: a) Potassium acetate, KC 2 H 3 O 2 Lets see some steps first.

13 Predicting Acids and Bases 1) Split the salt formula into ions 2) Which ion gets H + ? Write the formula 3) Which ion gets OH - ? Write the formula A) Potassium acetate, KC 2 H 3 O 2 KOH + HC 2 H 3 O 2 KC 2 H 3 O 2 + HOH OPPOSITES ATTRACT!

14 Predicting Acids and Bases Lithium fluoride, LiF HF + LiOH Li F + H 2 O

15 The pH Scale Revisited What is pH again? It expresses the acidity of a solution; the concentration of hydrogen ions Ranges from… 0 14 As pH decreases, the concentration of hydrogen ions increases, and the concentration of hydroxide ions decreases. In a neutral solution, the concentration of hydroxide ions and hydrogen ions are equal.

16 Acid-Base Indicators Methyl Red Color change ~pH 5 Below pH 5: red Above pH 5: yellow At 5? Orange (only a portion has been converted from yellow to red)

17 Acid-Base Indicators Bromthymol blue Color change ~pH 7 Below pH 7: yellow Above pH 7: blue At 7: greenish

18 Acid-Base Indicators Phenolphthalein Color change ~ pH 9 Below pH 9: colorless Above pH 9: pink At pH 9: very light pink


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