Learning Outcomes Experiment to classify acids and bases using their characteristic properties. (Ch 7) Include: indicators, pH, reactivity with metalsInclude: indicators, pH, reactivity with metals
Learning Outcomes Discuss the occurrence of acids and bases in biological systems, industrial processes, and domestic applications (Ch 8) Include: safety and health considerationsInclude: safety and health considerations
Learning Outcomes Explain how acids and bases interact to form a salt and water in the process of neutralization. (Ch 7)
Learning Outcomes Describe the formation and environmental impact of various forms of pollution. (Ch 8) Examples: acid precipitation, ground-level ozone, air-borne particulates, smog, ozone depletion, respiratory ailments & acidified lakes.
7.1 Common Acids and Bases Acids often occur naturally eg) Lactic acid in sore muscles (not enough oxygen present during work) eg) many fruits including citrus and pineapple
Properties Taste sour –Citric Acid C 6 H 8 O 7 Feel watery Caustic (corrosive) –They burn
Svante Arrhenius Found that acids are ionic compounds and when dissolved (aq) they separate into their ions. He defined acids as substances that produce hydrogen ions in solution.
HCl ions separate in water to make H+ and Cl - The more H + ions present in solution the stronger the acid
Bases Often found naturally in foods or prescription drugs. Materials which are bases are referred to as being basic or alkaline. –Eg) Quinine is a base found in cinchona bark and used to make tonic water and medicine for malaria. –Eg) bases are used to make soap. NaOH
Arrhenius found that bases are ionic compounds and when dissolved (aq) they separate into their ions. He defined bases as substances that produce hydroxide ions in solution. NaOH separates in solution to make Na+ and OH- NaOH separates in solution to make Na+ and OH- The more OH- ions present in solution the stronger the base The more OH- ions present in solution the stronger the base Na(OH) Na + + OH - Na(OH) Na + + OH -
NOTE: Ammonia NH 3 is a base when dissolved in water. Why? NH 3 + H 2 O NH 4 + + OH - NH 3 + H 2 O NH 4 + + OH - The ammonia atom steals one H from water to form OH- ammonia atom vs. ammonium ion
7.2 pH: A Powerful Scale Indicators – molecules which change colour with changes in the amount of H + (aq) ions or OH - (aq) ions present.
Eg) phenolphthalein turns red in base, stays clear in acidic and neutral conditions. turns red in base, stays clear in acidic and neutral conditions. CSI use this to determine presence of blood CSI use this to determine presence of blood Eg) Litmus paper Blue Red in Acid Blue Red in Acid Red Blue in Base Red Blue in Base
INDICATORS DO NOT TELL THE STRENGTH OF THE ACID OR BASE. Indicator Color in Acid Color in neutral water Color in Base Red Litmus No change Blue Blue Litmus Red No change PhenolphthaleinTurmeric Yellow RedRed
Note: VERY little indicator is needed in the tests. Too much indicator can change the pH of the acid or base. Example: Phenolphthalein is a weak acid.
The pH Scale pH – stands for “power of the hydrogen ion” a scale used to measure the strength of an acid or base. Is measured with an electronic pH meter OR by looking at the colours on Universal indicator paper. Note: neutral solutions have equal numbers of H+ and OH- ions.
Each change in 1 pH changes the strength by a factor of 10. Each change in 1 pH changes the strength by a factor of 10. Eg) pH 1 is 10 3 or 1000 times as strong an acid as pH 4.Eg) pH 1 is 10 3 or 1000 times as strong an acid as pH 4.Assignment -P 225 1-5 (21), BLM 7-7 & 7-8 -Fill out chart of important acids and bases in notes
BLM 7-8 1. Base 2. Acid 3. Neither 4. Neither 5. Base 6. Acid 7. Acid 8. Base 9. Neither 10. Acid 11. Acid 12. Acid
7.3 Properties of Acids and Bases The strength of an acid is determined by 2 factors: Concentration – how much acid is dissolved in water. Percent Ionization – the number of molecules that will ionize to release H+ ions for every 100 molecules dissolved.
Concentration Percent Ionization Concentrated Dilute H 2 CO 3 2H + + CO 3 2- 99mL HCl 1mL HCL 200 1 Weak 1mL H 2 O 99mL H 2 O H 2 SO 4 2H + + SO4 2- None all Strong
Note: For Percent Ionization the # of H+ ions in the acid DOES NOT DETERMINE THE STRENGTH OF THE ACID The strength is only determined by the amount of H+ ions that go into solution Not all acids release H+ ions equally easily. (Generally the more polar the bond the stronger the acid.)
Eg) CH 3 COOH has 4 H atoms but only 1 ionizes: CH 3 COOH CH 3 COO - + H + Acetic acid Copy the charts for common acids and bases on p 227. Why is ammonia considered a base when dissolved in water? HINT: Guess the products of NH 3 + H 2 O NH 3 + H 2 O = NH 4 + + OH -