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Acids and bases:Properties and definition
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
http://www.filipinoheritage.com/images/food/aug/kalamansi.jpg
acetic acid(CH3CO2H)
citric acid(C6H8O7)
hydrochloric acid(HCl)
We encounter bases in our daily lives
http://www.ultramega.com.ph/products-search.php?sub_cat_id=34http://www.pinegloproducts.com/catalog06/productscatalog/864oz/glass_ammoniacleaners/ammonia_lemon.gif
ammonia(NH3)
sodium hydroxide (NaOH)
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
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
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.
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
Acid-base reaction(aka neutralization reaction)
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.
When vinegar reacts with baking soda, water and carbon dioxide are produced
CH3CO2H + NaHCO3 NaCH3CO2 + H2CO3
H2CO3 H2O + CO2
Acid-base indicators
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.
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
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
pH
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
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
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
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
pH of some familiar aqueous solutions
Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.
Acid rain
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
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
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.
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.
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
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.
Acid rain is harmful to marble buildings and sculptures
1908 1969
Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.
Acid rain is harmful to the ecosystem
http://abacus.bates.edu/~ganderso/biology/bio270/clover_leaf_burns_pH2_30d.gifhttp://www.elmhurst.edu/~chm/vchembook/images2/195trout.gif
Honey, I told you not to leave your bike out in the rain!
Antacids
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
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.
http://www.unilab.com.ph/hcp/CMS_Files/kremilStablet_productshot1.jpghttp://www.maaloxus.com/assets/productImages/regularLiquid.jpg
Acid inhibitors prevent the production of gastric acids by acting on acid-producing
cells in the lining of the stomach
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