Post on 23-Feb-2016
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Acids and Bases in all Different Places
I. Properties of Acids
• A. Molecular substances which ionize when added to water to form hydronium (H3O+1) ions all acids are electrolytes
• B. React with active metals to form H2(g)
– 1. _ Mg(s) + _ HCl(aq) – 2. _ Zn(s) + _ HCl(aq) – 3. _ Cu(s) + _ HCl(aq)
I. Properties of Acids
• C. Acids affect the colors of indicators– Universal Indicator – Phenolphthalein
• D. Acids neutralize bases• E. Dilute acids taste sour think citric acid
and ascorbic acid (Vitamin C) • **SAFETY TIP: Acids release tremendous
amounts of heat when you dilute them – (esp. H2SO4) ALWAYS ADD ACID TO WATER
II. Naming Acids• treated as an ionic compound with H+1 (hydrogen ion) as
cation• negative ion can be nonmetal (binary acid) or polyatomic
anion (ternary acid) – A) Binary acids – acids that contain a negative ion ending in “-
ide”• 1) Formula Name
– use prefix: hydro-– use root of anion’s name– use suffix: -ic
• a) HCl b) HBr c) HF• hydrochloric acid hydrobromic acid hydrofluoric acid
II. Naming Acids
• 2) Name Formula– follow above rules in reverse– be sure to balance charges
• a) hydroiodic acid b) hydrosulfuric acid
• HI H2S
II. Naming Acids
• B) Ternary acids– DO NOT BEGIN WITH “hydro-“!!!!!!!– use name of polyatomic ion and switch its ending:
• NOTE: sulfur stays “sulfur-” + ending,
phosphorus stays “phosphor-” + ending
Ion Name Ending Acid Name ending
-ide Hydro- ____ -ic acid
-ate _________ -ic acid
II. Naming Acids• 1) Formula Name
– a) H2CO3
• CO3 carbonATE carbonic acid
– b) H2SO4
• SO4 sulfATE sulfuric acid
• 2) Name Formula– a) acetic acid
• acetIC acetATE HC2H3O2
– b) phosphoric acid• phosphorIC phosphATE H3PO4
– c) nitric acid• nitrIC nitrATE HNO3
** some acids are stronger than others:Acid Conjugate Base Ka Acid Conjugate
BaseKa
HI H+1 + I-1 very large H2CO3 H+1 + HCO3-1 4.3 x 10-7
HBr H+1 + Br-1 very large HSO3-1 H+1 + SO3
-2 1.1 x 10-7
HCl H+1 + Cl-1 very large H2S H+1 + HS-1 9.5 x 10-8
HNO3 H+1 + NO3-1 very large H2PO4
-1 H+1 + HPO4-2 6.2 x 10-8
H2SO4 H+1 + HSO4-1 large NH4
+1 H+1 + NH3 5.7 x 10-10
H2SO3 H+1 + HSO3-1 1.5 x 10-2 HCO3
-1 H+1 + CO3-2 5.6 x 10-11
HSO4-1 H+1 + SO4
-2 1.2 x 10-2 HPO4-2 H+1 + PO4
-3 2.2 x 10-13
H3PO4 H+1 + H2PO4-2 7.5 x 10-3 HS-1 H+1 + S-2 1.3 x 10-14
HF H+1 + F-1 6.3 x 10-4 H2O H+1 + OH-1 1.0 x 10-14
HNO2 H+1 + NO-1 5.6 x 10-4 OH-1 H+1 + O-2 < 10-36
HC2H3O2 H+1 + C2H3O2-1 1.8 x 10-5
Rank the following acids from weakest to strongest: sulfuric acid, carbonic acid, hydrochloric acid, hydrofluoric acid, acetic acid
H2CO3 , HC2H3O2 , HF, H2SO4 , HCl
III. Bases - ionic substance which dissociates to form hydroxide (OH-1) ions in water
* examples: lye (NaOH) , lime (Ca(OH)2) , milk of magnesia (Mg(OH)2)
• Naming Review. Name (or give the formula for) the following bases:• 1. NaOH• sodium hydroxide• 2. Mg(OH)2
• magnesium hydroxide• 3. aluminum hydroxide• Al(OH)3
• 4. ammonium hydroxide• NH4OH
IV. Properties of Bases - often referred to as caustic or alkaline substances
• A. Bases are electrolytes - dissociate in water to form OH-.
• B. Bases affect the colors of indicators.– Universal Indicator PURPLE– Phenolphthalein MAGENTA
• C. Bases neutralize acids.• D. Water solutions are bitter and slippery.• E. Emulsify fats and oils this is why they are
useful in soap
V. Salt – any ionic compound that does not contain hydroxide (OH-1)
• * all are good electrolytes
formed by a neutralization reactionAcid + Base Salt + Water
• 1) _____ HCl(aq) + _____ NaOH(aq)
• 2) _____ H2SO4(aq) + ____ KOH(aq)
• 3) ____ HBr(aq) + _____ Ca(OH)2(aq)
• 4) _____ HC2H3O2(aq) + _____ NaOH(aq)
Acid, Base, Salt, or Neither:
• 1. NaCl 2. KCl 3. KOH 4. SO2 5. NH4C2H3O2
• Salt salt base neither salt • 1. KBr 2. H2SO4 3. HgCl2 4. Al(OH)3 5. HCl• Salt acid salt base acid• 6. KOH 7. CaO 8. K3PO4 9. CO2 10. NH4OH• Base salt salt neither base
VI. pH – a mathematical way of measuring how acidic a solution is
pH Acidity
7 neutral
less than 7 acidic
greater than 7 basic
1 2 3 4 5 6 7 8 9 10 11 12 13
battery
acidlemon juice
vinegar milk sea water
milk of magnesia lye
H+10-1M 10-4M 10-7M 10-10M 10-13M
• It’s a logarithmic scale; that means each step is worth 10– lemon juice is 10 times more acidic than vinegar– battery acid is 10 times more acidic than lemon
juice– How many times more acidic is battery acid than
vinegar?
1 2 3 4 5 6 7 8 9 10 11 12 13
battery
acidlemon juice
vinegar milk sea water
milk of magnesia lye
H+10-1M 10-4M 10-7M 10-10M 10-13M
1 2 3 4 5 6 7 8 9 10 11 12 13
battery
acidlemon juice
vinegar milk sea water
milk of magnesia lye
H+10-1M 10-4M 10-7M 10-10M 10-13M
Color scale for Universal Indicator:
pH: 3 5 7 9 11
Red Orange Green Blue Purple
• Which of the solutions above is the most acidic?• Battery acid• 2) Which of the solutions above is the most basic? • Lye• 3) Look at the solutions that your teacher is testing
with universal indicator.– Label each as acidic, basic, or neutral– Estimate the pH based on the color– Rank the substances from most acidic to least acidic
Substance
acidic, basic, neutral pH
1
2
3
4
RANK:
VII. Buffer - a solution which is able to resist major changes in pH
• example: HC2H3O2(aq) H+1(aq) + C2H3O2
-1(aq)
• common-ion effect - by adding a salt with the negative ion (NaC2H3O2, KC2H3O2), we increase the concentration of that ion, therefore:
• add H+1: • the acid will react with the acetate ion to produce molecular
acetic acid, thus “neutralizing” it and keeping the pH the same• add OH-1: • the base will react with the molecular acetic acid to produce
acetate ions, thus “neutralizing” it and keeping the pH the same
BLOODY BUFFERS!!• biological example: carbonic acid/bicarbonate
in blood Hold your Breath!!!• There is a balance between the ions which
acts as a buffer, keeping the pH of the blood right around 7.4. The hemoglobin molecule in red blood cells can only withstand pH extremes of 7.2-7.6
VIII. Acid-Base Indicators - chemicals specifically designed to show specific
colors in acids and different colors in basesIndicator pH Range below pH color above pH color
methyl violet 0.0 – 1.6 yellow bluemethyl yellow 2.9 – 4.0 red yellow
bromophenol blue 3.0 – 4.6 yellow bluemethyl orange 3.2 – 4.4 red yellow
methyl red 4.8 – 6.0 red yellowlitmus 5.5 – 8.0 red blue
bromothymol blue 6.0 – 7.6 yellow bluephenol red 6.6 – 8.0 yellow red
phenolphthalein 8.2 – 10.6 colorless redthymolphthalein 9.4 – 10.6 colorless bluealizarin yellow 10.0 – 12.0 yellow red
IX. Acid-Base Neutralization
• if you have 35 molecules of acid, 35 molecules of base will neutralize it
• equivalence point - when an equivalent amount of OH-1 ions has been added to H+1 ions it’s “neutralized”
H+1 + OH-1 H2O
X. Acid-Base Titration - lab procedure used to determine the concentration of an unknown acid or base solution.
• standard solution – solution whose concentration is known
• unknown solution – solution whose concentration you are trying to determine
• MaVa = MbVb
Titration Problems
• 1) If you begin a titration with 20.0 mL of unknown HCl and titrate it to the equivalence point using 35.6 mL of 0.600 M standard NaOH, what is the concentration of HCl?
• Ma(20.0 mL) = (0.600M)(35.6 mL) Ma = 1.07 M
• 2) If you titrate 65.0 mL of an unknown NH3 solution to the equivalence point with 31.2 mL of a 1.50 M HCl solution, what is the concentration of the ammonia?
• (1.50M)(31.2mL) = Mb(65.0mL) Mb = 0.720 M
Titration Problems
• 1) Ma = ??? Va = 50.0 mL Mb = 1.50 M Vb = 71.3 mL
• Ma(50.0mL) = (1.50M)(71.3mL) Ma = 2.14 M
• 2) What is the concentration of an unknown NaOH solution if you titrate 100.0 mL of it to the equivalence point with 43.5 mL of 6.0 M HCl?
• (6.0M)(43.5mL) = Mb(100.0mL) Mb = 2.6 M
Titration Problems
• 3) What is the concentration of a vinegar (HC2H3O2) solution if you titrate exactly 20 drops of it to the equivalence point with 26 drops of 0.600M NaOH?
• Ma(2θdr) = (0.600M)(26dr) Ma = 0.78 M