Download - Acids and bases: Properties and definition. We encounter acids in our daily lives 20Acid.gif
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Acids and bases:Properties and definition
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We encounter acids in our daily lives
http://www.sunnysidecorp.com/images/Muriatic%20Acid.gifhttp://www.thekitchn.com/thekitchn/good-questions/what-can-i-do-with-datu-puti-filipino-coconut-vinegargoodquestions119557
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acetic acid(CH3CO2H)
citric acid(C6H8O7)
hydrochloric acid(HCl)
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We encounter bases in our daily lives
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ammonia(NH3)
sodium hydroxide (NaOH)
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An acid is a substance that produces H+ when dissolved in water
HX H+(aq) + X-
(aq) H2O
HCl H+(aq) + Cl-(aq)
H2O
Aqueous (or aq) is a solution wherein water is the solvent
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
CH3CO2H H+(aq) + CH3CO2
-(aq)
H2O
The double-headed arrow signifies that the reaction goes forward and reverse
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A base is a substance that produces OH- when dissolved in water
MOH M+(aq) + OH-
(aq) H2O
NaOH Na+(aq) + OH-
(aq) H2O
Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-
Hill.
NH3 NH4+
(aq) + OH-(aq)
H2O
The double-headed arrow signifies that the reaction goes forward and reverse
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Acids and bases have the following properties
Acids
• taste sour
• aqueous acid conducts electricity
Bases
• taste bitter
• feel slippery
• aqueous base conducts electricity
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
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Ions cause aqueous solutions to be good conductors
• to light the bulb, electric current must flow between the two wires
• ions carry electrical charge from one wire to another, thereby completing the circuit
copper wire
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Acid-base reaction(aka neutralization reaction)
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An acid-base reaction is a reaction between an acid and a base to form salt and water
acid + base salt + water
salt is an ionic compound made of a cation other than H+ and an anion other than OH- or O2-
HCl + NaOH NaCl + H2O
CH3CO2H + KOH KCH3CO2 + H2O
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
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When vinegar reacts with baking soda, water and carbon dioxide are produced
CH3CO2H + NaHCO3 NaCH3CO2 + H2CO3
H2CO3 H2O + CO2
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Acid-base indicators
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An indicator is a substance that is added to a solution. It turns one color in an acidic medium
and turns another color in a basic medium
• litmus paper
• phenolphthalein
Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd.
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Litmus paper contains various organic compounds. It changes color depending on the
acidity/basicity of a solution
http://www.britannica.com/EBchecked/topic/343896/litmushttp://oldwww.mtlsd.org/senior/science/JPtachcinski/Lab_Proc/Basic%20Science%20Lab%20Techniques_files/litmus.jpe
red to blue: base
blue to red: acid
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Phenolphthalein is colorless in acidic and neutral solutions but reddish pink in basic solutions
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.Skoog, D., D. West, and F.J. Holler. 1996. Fundamentals of Analytical Chemistry 7th ed. USA: Saunders College Publishing.
C OH
CO
OH OH
C
C
OO
O
OOH
colorless reddish pink
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pH
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pH is a logarithmic scale that indicates the amount of H+ in solution
pH = - log [H+]
where [H+] = concentration of H+ in units of molarity
= moles H+ / L of solution
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An HCl solution has [H+] = 1.00 x 10-6 M. Calculate for the pH of the solution
pH = - log [H+]
pH = - log [1.00 x 10-6]
= 6.00
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pH values indicate if a solution is acidic, neutral, or basic
• If pH < 7.00, solution is acidic
• If pH = 7.00, solution is neutral
• If pH > 7.00, solution is basic
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Schedule
• Feb 29– deadline for the submission of outline
• Mar 7 (4:30-6:00 pm)– LT # 3
• Mar 9-16– group reports
• Mar 21 (11:30-1:30, C-109)– finals
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pH of some familiar aqueous solutions
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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Acid rain
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Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
The effect of industrial society on the environment is especially apparent in the problem of acid rain
major substances involved in acid rain
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SO2 is converted to H2SO4
SO2 SO3
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
oxidation
SO3 + H2O H2SO4
from power plant emissions
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SO2 is converted to H2SO4
SO2 + H2O H2SO3
from coal
H2SO3 + H2O2 H2SO4 + H2O
air pollutant
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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Nitrogen oxides (NOx) are converted to HNO3
N2 + O2 NOx
NOx N2O5
at night,
N2O5 + H2O HNO3
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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NO is converted to NO2 and HNO3
NO NO2 + HNO3
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
from combustion in car engines and
electric power plants
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The pH of rain and snow has adversely declined in many parts of the world
• Much of the United States– as early as 1984, average rainfall pH = 4.2
• Sweden– rain with pH = 2.7 (about the same as
vinegar) has been observed
• West Virginia– rain with pH = 1.8 (between lemon juice and
stomach acid) has been observed
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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Acid rain is harmful to marble buildings and sculptures
1908 1969
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
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Acid rain is harmful to the ecosystem
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Honey, I told you not to leave your bike out in the rain!
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Antacids
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It is natural to have HCl in the stomach, but the problem occurs when the amount of HCl is too high
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
CO2 + H2O H2CO3
H2CO3 H+ + HCO3-
in the blood plasma,
by-product of metabolism
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To temporarily reduce the amount of HCl in the stomach, an antacid may be taken. The HCl and
the antacid undergo an acid-base reaction
Kremil-S and Maalox contain Al(OH)3 and Mg(OH)2
3HCl +Al(OH)3 AlCl3 + 3H2O
2HCl +Mg(OH)2 MgCl2 + 2H2O
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
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Acid inhibitors prevent the production of gastric acids by acting on acid-producing
cells in the lining of the stomach
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