Presentation on theme: "ACIDS AND BASES UNIT 10 General Chemistry Spring 2010."— Presentation transcript:
ACIDS AND BASES UNIT 10 General Chemistry Spring 2010
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)
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)
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
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
pH Means potency of hydrogen Refers to pondus hydrogenii (potential hydrogen)
The pH Scale
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 -
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 -
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
Neutralization Reactions Example B) H 2 SO NaOH Na 2 SO 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.
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.
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!
Predicting Acids and Bases Lithium fluoride, LiF HF + LiOH Li F + H 2 O
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.
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)
Acid-Base Indicators Bromthymol blue Color change ~pH 7 Below pH 7: yellow Above pH 7: blue At 7: greenish
Acid-Base Indicators Phenolphthalein Color change ~ pH 9 Below pH 9: colorless Above pH 9: pink At pH 9: very light pink