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Acids, Bases  & Salts Copyright Sautter 2003
The next slide is a quick promo for my books  after which the presentation will begin Thanks for your patience! Walt S. [e...
Books available at: www. wsautter .com www.smashwords.com www.amazon.com www.bibliotastic.com www.goodreads.com Walt’s Boo...
ACIDS ,  BASES  &  SA LTS WHAT IS AN ACID ? WHAT IS A BASE ? WHAT ARE THE PROPERTIES OF ACIDS AND BASES ? WHAT ARE THE DIF...
PROPERTIES OF ACIDS <ul><li>CONTRARY TO COMMON BELIEF ACIDS DO NOT  ATTACK ALL SUBSTANCES. MANY ARE VITAL TO OUR VERY EXIS...
PROPERTIES OF BASES <ul><li>(1) BASES TASTE BITTER (MEDICINES ARE OFTEN BASES THUS THE TERM “BITTER MEDICINE”) </li></ul><...
DEFINITION OF ACIDS  AND  BASES <ul><li>ACIDS AND BASES AND THE REACTIONS WHICH RESULT CAN BE DESCRIBED USING SEVERAL DIFF...
THE ARRENHIUS OR TRADITIONAL  ACID  –  BASE  THEORY <ul><li>AN ACID IS A SUBSTANCE WHICH RELEASES HYDROGEN IONS (H + )  IN...
COMMON  ACIDS  &  BASES <ul><li>HYDROCHLORIC ACID (STOMACH ACID) – HCl </li></ul><ul><li>ACETIC ACID (VINEGAR) – HC 2 H 3 ...
THE BRONSTED – LOWRY  ACID  AND  BASE  THEORY <ul><li>AN ACID IS A PROTON DONOR. A PROTON IN SOLUTION CONSISTS OF A HYDROG...
A CLOSER LOOK AT BRONSTED – LOWRY  ACID  –  BASE  REACTIONS <ul><li>(1)  WATER CAN ACT AS A BASE. AT TIMES IT CAN EVEN ACT...
LEWIS ACID – BASE THEORY <ul><li>THE LEWIS ACID – BASE THEORY EXPANDS THE ARRENHIUS AND BRONSTED LOWRY THEORIES TO INCLUDE...
WHERE DO  ACIDS  &  BASES  COME FROM? <ul><li>ACIDS RESULT FROM THE ADDITION OF NONMETAL OXIDES TO WATER. THESE OXIDES ARE...
ACID  &  BASE  STRENGTH <ul><li>WHEN DISSOLVED SUBSTANCES SEPARATE INTO FREE MOBILE IONS THIS IS CALLED DISSOCIATION.  </l...
COMMON STRONG ACIDS   <ul><li>STRONG ACIDS </li></ul><ul><li>HCLO 4  PERCHLORIC ACID </li></ul><ul><li>HI  HYDROIODIC ACID...
COMMON STRONG BASES <ul><li>STRONG BASES </li></ul><ul><li>LiOH  LITHIUM HYDROXIDE </li></ul><ul><li>NaOH  SODIUM HYDROXID...
PH OF SOLUTIONS <ul><li>PH IS A CONVENIENT SYSTEM FOR THE MEASURING THE ACIDITY OF A SOLUTION. </li></ul><ul><li>PH IS DEF...
PH OF SOLUTIONS (CONT’D) <ul><li>PH = - LOG [H + ]  </li></ul><ul><li>P MEANS NEGATIVE LOG AND THE  BRACKETS AROUND H +  M...
THE PH SCALE  <ul><li>0  1  2  3  4  5  6   7   8  9  10  11  12  13  14 </li></ul>ACID  RANGE BASE  RANGE NEUTRAL LOW PH ...
POH OF SOLUTIONS <ul><li>POH = - LOG [OH - ]  </li></ul><ul><li>WHERE THE  BRACKETS AROUND OH -  MEANS “CONCENTRATION OF O...
FORMATION OF A HYDROGEN ION  (AN AQUEOUS PROTON) H 1 P + 0 N 0 1 e - + ONLY A PROTON REMAINS A HYDROGEN ATOM LOSES ITS ELE...
STRONG & WEAK  ACID   DISSOCIATION H NO 3 NO 3 + - STONG ACIDS DISSOCIATE READILY (NITRIC ACID HNO 3 ) WEAK ACIDS DISSOCIA...
COMPARISON OF  ACID  AND  BASE STRENGTHS   FOR SEVERAL ACIDS HClO 4      H +   +  ClO 4 - HCl    H +   +  Cl - HF     H...
ACID -  BASE  NEUTRALIZATION H + (aq)  +  OH - (aq)      H 2 O (l) H+ H+ H+ H+ H+ H+ H+ OH - OH - OH - OH - OH - OH - OH ...
NAMING OF  ACIDS (NOMENCLATURE) <ul><li>ACIDS ARE OF TWO TYPES FOR NAMING PURPOSES </li></ul><ul><li>(1) BINARY ACIDS – CO...
NAMING BINARY  ACIDS <ul><li>BINARY ACIDS ARE COMPOSED OF TWO ELEMENTS NOT NECESSARILY JUST TWO ATOMS. FOR EXAMPLE, H 2 S ...
NAMING TERNARY ( OXYACIDS ) <ul><li>TERNARY ACIDS ARE COMPOSED OF THREE ELEMENTS NOT NECESSARILY JUST THREE ATOMS. FOR EXA...
NAMING TERNARY ( OXYACIDS )  (CONT’D) <ul><li>FOR EXAMPLE H 2 SO 3  CONTAINS THE ANION SO 3 -2  , SULFITE ION. THE ACID NA...
ADVANCED ACID - BASE  CONCEPTS
ADVANCED  ACID  BASE  CHEMISTRY ( ACID CONSTANTS ) <ul><li>A MEASURE OF ACID STRENGTH IS THE EQUILIBRIUM CONSTANT (K a ). ...
ADVANCED  ACID   BASE  CHEMISTRY ACID CONSTANTS   (CONT’D) <ul><li>THE STRENGTH OF AN ACID DEPENDS ON THE DEGREE OF DISSOC...
ADVANCED  ACID   BASE  CHEMISTRY ACID CONSTANTS  (CONT’D) <ul><li>ACID CONSTANT FOR SOME COMMON ACIDS </li></ul>ACID  K a ...
CALCULATING HYDROGEN AND HYDROXIDE CONCENTRATIONS <ul><li>PURE WATER CONTAINS VERY SMALL CONCENTRATIONS OF BOTH HYDROGEN A...
PH OF A STRONG ACID <ul><li>WHAT IS THE PH OF 2.0 LITERS OF NITRIC ACID SOLUTION WHICH CONTAINS 15.75 GRAMS OF THE ACID? <...
CALCULATING HYDROGEN AND HYDROXIDE CONCENTRATIONS (CONT’D) <ul><li>USING THE K w  CONSTANT FOR THE DISSOCIATION OF PURE WA...
PH OF WEAK ACIDS (CALCULATIONS USING K a ) <ul><li>FOR A WEAK ACID HX </li></ul><ul><li>HX (aq)    H + (aq)  +  X - (aq)...
CALCULATIONS INVOLVING  WEAK BASES <ul><li>THE PH OF A 0.10 M AMMONIA SOLUTION IS 11.37. WHAT IS THE K b  FOR NH 3  ?  </l...
TITRATION <ul><li>TITRATION REFERS TO THE ADDITION OF AN ACID AND BASE IN MEASURED QUANTITIES. OFTEN THE TITRATION IS CARR...
TITRATION (CONT’D) STRONG ACID (HCl) STRONG BASE (KOH) WEAK  ACID (HF) WEAK BASE (NH 3 ) NEUTRAL PH = 7.00 ACIDIC PH < 7.0...
NORMALITY AND TITRATION <ul><li>NORMALITY IS A SYSTEM OF MEASURING THE CONCENTRATION OF SOLUTIONS WHICH IS OFTEN USED IN T...
NORMALITY AND TITRATION (CONT’D) <ul><li>A MOLE OF H +  IONS OR OH -  IONS IS CALLED AN  EQUIVALENT.  THEREFORE NORMALITY ...
NORMALITY AND TITRATION (CONT’D) <ul><li>THE NORMALITY OF AN BASE CAN BE RELATED TO ITS MOLARITY BY THE  NUMBER OF REPLACE...
TITRATION CALCULATIONS (STRONG ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HCl 0....
TITRATION CALCULATIONS (CONT’D) (STRONG ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS ...
pH 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Equivalent point moles acid = moles base Titration of Strong Acid vs Strong Base Volume...
TITRATION CALCULATIONS (WEAK ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HAc 0.10...
TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) <ul><li>K a  = 1.8 x 10 -5 ,  [H + ] = X  </li></ul><ul><li>HAc ...
<ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HAc 0.10 M WITH 100 MLS OF NaOH 0.10 M.(Hac = HC 2 H 3 O ...
<ul><li>SINCE ONLY A SALT SOLUTION IS PRESENT THE QUESTION NOW BECOMES, “WHAT IS THE PH OF A 0.080 M SOLUTION OF NaAc ?” <...
TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) <ul><li>EQUATIONS: </li></ul><ul><li>(1) HAc  +  NaOH    NaAc  ...
pH 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Equivalent point moles acid = moles base Titration of Weak  Acid vs Strong Base Volume ...
NORMALITY AND TITRATION (CONT’D) <ul><li>AT THE END POINT OF ACID – BASE TITRATION (ALSO CALLED EQUIVALENCE POINT), MOLES ...
BUFFERS <ul><li>WHAT IS A BUFFER?  </li></ul><ul><li>A WEAK ACID AND ITS SALT OR A WEAK BASE AND ITS SALT. </li></ul><ul><...
BUFFERS (CONT’D) <ul><li>LE CHATELIER’S PRINCIPLE STATED THAT A SYSTEM AT EQUILIBRIUM CONSUME ADDED REACTANTS OR PRODUCTS ...
BUFFERS (CONT’D) <ul><li>SUMMARY OF EFFECTS OF ADDING AN ACID TO AN ACIDIC BUFFER: </li></ul><ul><li>[WEAK ACID]  ,  [CONJ...
BUFFERS (CONT’D) <ul><li>WHAT IS THE PH OF A BUFFER THAT CONSISTS OF 0.10 M HAc AND 0.05 M NaAc ? </li></ul><ul><li>HAc  ...
ADDING ACID TO AN  UNBUFFERED  SYSTEM <ul><li>HOW DOES THE PH OF A LITER OF WATER CHANGE WHEN 0.0001 MOLES OF HCl ARE ADDE...
ADDING ACID TO AN  BUFFERED  SYSTEM <ul><li>HOW DOES THE PH OF A LITER OF A BUFFER COMPOSED OF 0.10 M HAc AND 0.05 M NaAc ...
ADDING ACID TO AN  UNBUFFERED  SYSTEM <ul><li>[HAc] eq  = 0.1001 MOLES / 1 LITER = 0.1001 M </li></ul><ul><li>[Ac - ] eq  ...
THE END
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Acids, Bases and Salts

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Discusses the definitions, properties and calculations associated with acid / base chemistry
**More good stuff available at:
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Transcript of "Acids, Bases and Salts"

  1. 1. Acids, Bases & Salts Copyright Sautter 2003
  2. 2. The next slide is a quick promo for my books after which the presentation will begin Thanks for your patience! Walt S. [email_address]
  3. 3. Books available at: www. wsautter .com www.smashwords.com www.amazon.com www.bibliotastic.com www.goodreads.com Walt’s Books for Free!
  4. 4. ACIDS , BASES & SA LTS WHAT IS AN ACID ? WHAT IS A BASE ? WHAT ARE THE PROPERTIES OF ACIDS AND BASES ? WHAT ARE THE DIFFERENT KINDS OF ACIDS AND BASES ? HOW ARE ACIDS AND BASES NAMED?
  5. 5. PROPERTIES OF ACIDS <ul><li>CONTRARY TO COMMON BELIEF ACIDS DO NOT ATTACK ALL SUBSTANCES. MANY ARE VITAL TO OUR VERY EXISTENCE ! </li></ul><ul><li>ALL ACIDS DO HOWEVER HAVE SEVERAL COMMON CHARACTERISTICS. </li></ul><ul><li>(1) ACIDS TASTE SOUR </li></ul><ul><li>(2) ACIDS TURN LITMUS RED (LITMUS IS A DYE THAT CHANGES COLOR DEPENDING ON ACIDITY) </li></ul><ul><li>(3) ACIDS REACT WITH ACTIVE METALS TO FORM HYDROGEN GAS </li></ul><ul><li>(4) ACIDS REACT WITH BASES TO FORM SALTS AND WATER </li></ul>I’VE GOT TOO MUCH HCl !
  6. 6. PROPERTIES OF BASES <ul><li>(1) BASES TASTE BITTER (MEDICINES ARE OFTEN BASES THUS THE TERM “BITTER MEDICINE”) </li></ul><ul><li>(2) BASES TURN LITMUS BLUE </li></ul><ul><li>(3) BASES FEEL SLIPPERY </li></ul><ul><li>(4) BASES REACT WITH ACIDS TO FORM SALTS AND WATER </li></ul>
  7. 7. DEFINITION OF ACIDS AND BASES <ul><li>ACIDS AND BASES AND THE REACTIONS WHICH RESULT CAN BE DESCRIBED USING SEVERAL DIFFERENT THEORIES. </li></ul><ul><li>THE THREE MOST COMMON THEORIES ARE: </li></ul><ul><li>(1) THE ARRENHIUS OR TRADITIONAL THEORY </li></ul><ul><li>(2) THE BRONSTED – LOWRY THEORY </li></ul><ul><li>(3) THE LEWIS THEORY </li></ul><ul><li>EACH OF THE THREE THEORIES VIEW ACIDS AND BASES SLIGHTLY DIFFERENTLY BUT THEY DO NOT CONTRADICT EACHOTHER IN ANY WAY. ONE MERELY EXPANDS ON THE OTHER ! </li></ul>
  8. 8. THE ARRENHIUS OR TRADITIONAL ACID – BASE THEORY <ul><li>AN ACID IS A SUBSTANCE WHICH RELEASES HYDROGEN IONS (H + ) IN SOLUTION. </li></ul><ul><li>HNO 3(aq)  H + ( aq) + NO 3 - (aq) </li></ul><ul><li>A BASE IS A SUBSTANCE WHICH RELEASES HYDROXIDE IONS (OH - ) IN SOLUTION. </li></ul><ul><li>NaOH (S)  Na + (aq) + OH - ( aq) </li></ul><ul><li>WHEN AN ACID AND BASE REACT (A REACTION CALLED NEUTRALIZATION), A SALT AND WATER ARE FORMED. </li></ul><ul><li>HNO 3(aq) + NaOH (aq)  NaNO 3 (aq) + H 2 O (l) </li></ul><ul><li>(acid) (base) (salt) (water) </li></ul>
  9. 9. COMMON ACIDS & BASES <ul><li>HYDROCHLORIC ACID (STOMACH ACID) – HCl </li></ul><ul><li>ACETIC ACID (VINEGAR) – HC 2 H 3 O 2 </li></ul><ul><li>CARBONIC ACID (SODA WATER) – H 2 CO 3 </li></ul><ul><li>SODIUM HYDROXIDE (DRAINO) – NaOH </li></ul><ul><li>AMMONIA WATER (CLEANING AGENT) – NH 4 OH </li></ul><ul><li>ALUMINUM HYDROXIDE (ROLAIDS) – Al(OH) 3 </li></ul><ul><li>MAGNESIUM HYDROXIDE (TUMS) – Mg(OH) 2 </li></ul>
  10. 10. THE BRONSTED – LOWRY ACID AND BASE THEORY <ul><li>AN ACID IS A PROTON DONOR. A PROTON IN SOLUTION CONSISTS OF A HYDROGEN ION (H + ). (HYDROGEN WITH AN ATOMIC NUMBER OF ONE AND A MASS NUMBER OF ONE HAS ONE PROTON, NO NEUTRONS AND AFTER LOSING ONE ELECTRON TO FORM AN ION, HAS NO ELECTRONS.) </li></ul><ul><li>A BASE IS A PROTON ACCEPTOR AND IT NEED NOT CONTAIN HYDROXIDE IONS. </li></ul><ul><li>AN ACID – BASE REACTION CONSISTS OF A PROTON TRANSFER FROM AN ACID TO A BASE. WHEN THIS OCCURS A NEW ACID AND BASE ARE FORMED. THIS IS BRONSTED- LOWRY NEUTRALIZATION. </li></ul><ul><li>HCl (aq) + H 2 O (aq)  H 3 O + (aq) + Cl - (aq) </li></ul><ul><li>(acid) (base) (new acid) (new base) </li></ul>
  11. 11. A CLOSER LOOK AT BRONSTED – LOWRY ACID – BASE REACTIONS <ul><li>(1) WATER CAN ACT AS A BASE. AT TIMES IT CAN EVEN ACT AS A ACID.. THE TERM IS AMPHIPROTIC MEANS THAT IT CAN BE EITHER DEPENDING ON THE SITUATION. </li></ul><ul><li>WHEN WATER ACTS AS A BASE H 3 O + ION IS FORMED. THIS CALLED HYDRONIUM ION . </li></ul><ul><li>THE ORIGINAL BASE (H 2 O) AFTER RECEIVING THE PROTON CAN NOW FUNCTION AS AN ACID IN THE REVERSE REACTION. HYDRONIUM ION IS CALLED THE CONJUGATE ACID OF THE BASE WATER IN THIS REACTION. </li></ul><ul><li>THE ORIGINAL ACID (HCl)AFTER LOSING THE PROTON CAN NOW FUNCTION AS AN BASE IN THE REVERSE REACTION. CHLORIDE ION IS CALLED THE CONJUGATE BASE OF THE ACID HYDROCHLORIC ACID IN THIS REACTION. </li></ul>HCl (aq) + H 2 O (aq)  H 3 O + (aq ) + Cl - (aq) H+ H+ acid base conjugate acid conjugate acid
  12. 12. LEWIS ACID – BASE THEORY <ul><li>THE LEWIS ACID – BASE THEORY EXPANDS THE ARRENHIUS AND BRONSTED LOWRY THEORIES TO INCLUDE EVEN MORE SUBSTANCES WHICH HAVE BEEN FOUND EXPERIMENTALLY TO BE ACIDIC OR BASIC BUT NOT COMPLETELY EXPLAINED BY EITHER. </li></ul><ul><li>THE LEWIS THEORY DESCRIBES ACIDS AS ELECTRON PAIR ACCEPTORS AND BASES AS ELECTRON PAIR DONORS. AS A RESULT THE OBSERVED ACIDIC PROPERTIES OF METAL IONS IN SOLUTION CAN BE EXPLAINED. </li></ul><ul><li>ADDITIONALLY, THE BASIC PROPERTIES OF SUBSTANCES SUCH AS AMMONIA CAN AS BE EXPLAINED AS ELECTRON PAIR DONORS EVEN THOUGH AMMONIA CONTAINS NO HYDROXIDE IONS. </li></ul>
  13. 13. WHERE DO ACIDS & BASES COME FROM? <ul><li>ACIDS RESULT FROM THE ADDITION OF NONMETAL OXIDES TO WATER. THESE OXIDES ARE CALLED ACID ANHYDRIDES (ACIDS WITHOUT WATER). EVEN CARBON DIOXIDE WHEN ADDED TO WATER WILL MAKE THE SOLUTION MILDLY ACIDIC. </li></ul><ul><li>CO 2(g) + H 2 O (l)  H 2 CO 3(aq) (CARBONIC ACID) </li></ul><ul><li>SO 2(g) + H 2 O (l)  H 2 SO 3 (aq) (SULFUROUS ACID) </li></ul><ul><li>BASES ARE FORMED BY METALLIC OXIDES AND WATER. THEY ARE CALLED BASIC ANHYDRIDES. </li></ul><ul><li>CaO (s) + H 2 O (l)  Ca(OH) 2(s) (CALCIUM HYDROXIDE) </li></ul><ul><li>Na 2 O (s) + H 2 O (l)  2 NaOH (s) (SODIUM HYDROXIDE) </li></ul>
  14. 14. ACID & BASE STRENGTH <ul><li>WHEN DISSOLVED SUBSTANCES SEPARATE INTO FREE MOBILE IONS THIS IS CALLED DISSOCIATION. </li></ul><ul><li>THE STRENGTH OF ACIDS AND BASES DEPENDS ON THEIR ABILITY TO DISSOCIATE IN SOLUTION. </li></ul><ul><li>CONCENTRATION REFERS TO THE MOLARITY OF THE SOLUTION. </li></ul><ul><li>CONCENTRATION AND STRENGTH DO NOT MEAN THE SAME THING BUT ARE RELATED. </li></ul><ul><li>THERE ARE SEVERAL STRONG ACIDS AND BASES. THESE DISSOCIATE WELL (~ 100%). ALL OTHER ACIDS AND BASES ARE WEAK (DISSOCIATE POORLY) </li></ul>
  15. 15. COMMON STRONG ACIDS <ul><li>STRONG ACIDS </li></ul><ul><li>HCLO 4 PERCHLORIC ACID </li></ul><ul><li>HI HYDROIODIC ACID </li></ul><ul><li>HBr HYDROBROMIC ACID </li></ul><ul><li>HCl HYDROCHLORIC ACID </li></ul><ul><li>HNO 3 NITRIC ACID </li></ul><ul><li>H 2 SO 4 SULFURIC ACID </li></ul>
  16. 16. COMMON STRONG BASES <ul><li>STRONG BASES </li></ul><ul><li>LiOH LITHIUM HYDROXIDE </li></ul><ul><li>NaOH SODIUM HYDROXIDE </li></ul><ul><li>KOH POTASSIUM HYDROXIDE </li></ul><ul><li>RbOH RUBIDIUM HYDROXIDE </li></ul><ul><li>CsOH CESIUM HYDROXIDE </li></ul><ul><li>Ca(OH) 2 CALCIUM HYDROXIDE </li></ul><ul><li>Sr(OH) 2 STRONTIUM HYDROXIDE </li></ul><ul><li>Ba(OH) 2 BARIUM HYDROXIDE </li></ul>
  17. 17. PH OF SOLUTIONS <ul><li>PH IS A CONVENIENT SYSTEM FOR THE MEASURING THE ACIDITY OF A SOLUTION. </li></ul><ul><li>PH IS DEFINED AS THE NEGATIVE LOGARITHM OF THE HYDROGEN ION CONCENTRATION IN A SOLUTION. </li></ul><ul><li>A LOGARITHM (LOG) IS A POWER OF 10. IF A NUMBER IS WRITTEN AS 10 X THEN ITS LOG IS X. </li></ul><ul><li>FOR EXAMPLE 100 COULD BE WRITTEN AS 10 2 THEREFORE THE LOG OF 100 IS 2. </li></ul><ul><li>IN CHEMISTRY CALCULATIONS OFTEN SMALL NUMBERS ARE USED LIKE .0001 OR 10 -4 . THE LOG OF .0001 IS THEREFORE –4. </li></ul><ul><li>FOR NUMBERS THAT ARE NOT NICE EVEN POWERS OF 10 A CALCULATOR IS USED TO FIND THE LOG VALUE. FOR EXAMPLE THE LOG OF .00345 IS –2.46 AS DETERMINED BY THE CALCULATOR. </li></ul>
  18. 18. PH OF SOLUTIONS (CONT’D) <ul><li>PH = - LOG [H + ] </li></ul><ul><li>P MEANS NEGATIVE LOG AND THE BRACKETS AROUND H + MEANS “CONCENTRATION OF H + ” </li></ul><ul><li>SAMPLE PROBLEM : </li></ul><ul><li>WHAT IS THE PH OF A SOLUTION WHEN ITS [H + ] = 0.000001 M ? </li></ul><ul><li>SOLUTION: </li></ul><ul><li>0.000001 = 10 -6 </li></ul><ul><li>PH = - LOG (10 -6 ) = - ( -6.00) = 6.00 </li></ul>
  19. 19. THE PH SCALE <ul><li>0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 </li></ul>ACID RANGE BASE RANGE NEUTRAL LOW PH VALUES INDICATE HIGH ACIDITY HIGH PH VALUE INDICATE HIGH BASITY 7.00 IS THE PH OF PURE WATER PH , [H + ] AND [OH - ] PH , [H + ] AND [OH - ] [H + ] = 1.00 x 10 -7 M IN PURE WATER PH = - LOG (1.00 x 10 -7 ) = 7.00
  20. 20. POH OF SOLUTIONS <ul><li>POH = - LOG [OH - ] </li></ul><ul><li>WHERE THE BRACKETS AROUND OH - MEANS “CONCENTRATION OF OH - ” </li></ul><ul><li>SAMPLE PROBLEM : </li></ul><ul><li>WHAT IS THE POH OF A SOLUTION WHEN ITS [OH - ] = 0.00001 M ? </li></ul><ul><li>SOLUTION: </li></ul><ul><li>0.00001 = 10 -5 </li></ul><ul><li>POH = - LOG (10 -5 ) = - ( -5.00) = 5.00 </li></ul><ul><li>PH + POH = PK w = 14.0 </li></ul><ul><li>PH = 14.0 –5.0 = 9.0, THE SOLUTION IS BASIC </li></ul>*
  21. 21. FORMATION OF A HYDROGEN ION (AN AQUEOUS PROTON) H 1 P + 0 N 0 1 e - + ONLY A PROTON REMAINS A HYDROGEN ATOM LOSES ITS ELECTRON TO FORM A HYDROGEN ION Atomic number 1 Atomic mass 1
  22. 22. STRONG & WEAK ACID DISSOCIATION H NO 3 NO 3 + - STONG ACIDS DISSOCIATE READILY (NITRIC ACID HNO 3 ) WEAK ACIDS DISSOCIATE POORLY (HYDROFLOURIC ACID HF) H (aq) (aq) FREE MOBILE IONS READILY FORM ALL MOLECULES DISSOCIATE F F F F + (aq) - (aq) FREE MOBILE IONS FORM BUT WITH DIFFICULTLY FEW MOLECULES DISSOCIATE
  23. 23. COMPARISON OF ACID AND BASE STRENGTHS FOR SEVERAL ACIDS HClO 4  H + + ClO 4 - HCl  H + + Cl - HF  H + + F - HCOOH  H + + HCOO - HC 2 H 3 O 2  H + + C 2 H 3 O 2 - NH 4 +  H + + NH 3 BASE GETS S T R O N G E R ACID GETS S T R O N G E R STRONGEST ACID WEAKEST CONJUGATE BASE STRONGEST BASE WEAKEST CONJUGATE ACID
  24. 24. ACID - BASE NEUTRALIZATION H + (aq) + OH - (aq)  H 2 O (l) H+ H+ H+ H+ H+ H+ H+ OH - OH - OH - OH - OH - OH - OH - ACID BASE 2 H O 2 H O 2 H O 2 H O
  25. 25. NAMING OF ACIDS (NOMENCLATURE) <ul><li>ACIDS ARE OF TWO TYPES FOR NAMING PURPOSES </li></ul><ul><li>(1) BINARY ACIDS – CONSIST OF TWO ELEMENTS ONE OF WHICH IS HYDROGEN </li></ul><ul><li>(2) TERNARY ACIDS – CONSIST OF THREE ELEMENTS ONE OF WHICH IS HYDROGEN AND ANOTHER OXYGEN. THESE ARE ALSO CALLED OXYACIDS </li></ul>HELLO MY NAME IS:
  26. 26. NAMING BINARY ACIDS <ul><li>BINARY ACIDS ARE COMPOSED OF TWO ELEMENTS NOT NECESSARILY JUST TWO ATOMS. FOR EXAMPLE, H 2 S CONSISTS OF JUST HYDROGEN AND SULFUR AND IS THEREFORE BINARY EVEN THOUGH IT HAS THREE ATOMS ! </li></ul><ul><li>ALL BINARY ACID NAMES BEGIN WITH “HYDRO” AND END IN “IC”. THE NAME OF THE NON HYDROGEN ELEMENT LIES INBETWEEN THE PREFIX AND SUFFIX OF THE NAME. </li></ul><ul><li>FOR EXAMPLE, H 2 S IS NAMED “ HYDRO SULFUR IC ACID” </li></ul><ul><li>HBr IS NAMED “ HYDRO BROM IC ACID” </li></ul>
  27. 27. NAMING TERNARY ( OXYACIDS ) <ul><li>TERNARY ACIDS ARE COMPOSED OF THREE ELEMENTS NOT NECESSARILY JUST THREE ATOMS. FOR EXAMPLE, H 2 SO 4 IS COMPOSED OF HYDROGEN, SULFUR AND OXYGEN EVEN THOUGH IT CONTAINS SEVEN ATOMS. </li></ul><ul><li>NAMING TERNARY ACIDS REQUIRES THAT YOU KNOW HOW TO NAME THE ANION THAT IS CONTAINED IN THE ACID. IN H 2 SO 4 THE NEGATIVE ION IS SO 4 -2 , SULFATE ION. </li></ul><ul><li>WHEN THE ANION NAME ENDS IN “ATE” THE ACID NAME ENDS IN “IC”. </li></ul><ul><li>THE NAME FOR H 2 SO 4 IS THEREFORE “SULFUR IC ACID” </li></ul><ul><li>THE NAME FOR HNO 3, WHICH CONTAINS THE NITRATE ION, NO 3 - , IS “NITR IC ACID” </li></ul>
  28. 28. NAMING TERNARY ( OXYACIDS ) (CONT’D) <ul><li>FOR EXAMPLE H 2 SO 3 CONTAINS THE ANION SO 3 -2 , SULFITE ION. THE ACID NAME THEREFORE IS “SULFUR OUS ACID” </li></ul><ul><li>WHEN THE NAME OF THE ANION CONTAINED IN THE ACID ENDS IN “ITE” THE ACID NAME ENDS IN “OUS”. </li></ul><ul><li>THE NAME FOR HNO 2 , WHICH CONTAINS NO 2 - , THE NITRITE ION IS “NITR OUS ACID” </li></ul>
  29. 29. ADVANCED ACID - BASE CONCEPTS
  30. 30. ADVANCED ACID BASE CHEMISTRY ( ACID CONSTANTS ) <ul><li>A MEASURE OF ACID STRENGTH IS THE EQUILIBRIUM CONSTANT (K a ). LIKE ALL EQUILIBRIUM CONSTANTS IT IS CALCULATED BY DIVIDING EQUILIBRIUM PRODUCT CONCENTRATIONS BY REACTANT CONCENTRATIONS. </li></ul><ul><li>THIS MEANS THAT THE SIZE OF K a WILL INDICATE RELATIVE ACID STRENGTH. SINCE PRODUCT CONCENTRATIONS ARE PLACED IN THE NUMERATOR OF THE CALCULATION, AS THEY INCREASE, K a ALSO INCREASES. IF K a IS SMALL, FEW PRODUCTS ARE FORMED. </li></ul>*
  31. 31. ADVANCED ACID BASE CHEMISTRY ACID CONSTANTS (CONT’D) <ul><li>THE STRENGTH OF AN ACID DEPENDS ON THE DEGREE OF DISSOCIATION OF THE ACID (CONCENTRATIONS OF PRODUCT IONS FORMED) </li></ul><ul><li>AS K a INCREASES, ACID STRENGTH INCREASES </li></ul><ul><li>SINCE THE STRENGTH OF AN ACID IS INVERSELY RELATED TO THE STRENGTH OF ITS CONJUGATE BASE, AS K a FOR AN ACID INCREASES, THE STRENGTH OF ITS CONJUGATE DECREASES. </li></ul><ul><li>BASES STRENGTHS ARE OFTEN MEASURED BY K b VALUES. </li></ul><ul><li>K w = K a x K b </li></ul><ul><li>(REMEMBER K w ALWAYS EQUALS 1.00 x 10 -14 ) </li></ul>*
  32. 32. ADVANCED ACID BASE CHEMISTRY ACID CONSTANTS (CONT’D) <ul><li>ACID CONSTANT FOR SOME COMMON ACIDS </li></ul>ACID K a HYDROCHLORIC UNDEFINED NITRIC UNDEFINED HYDROFLOURIC 6.7 x 10 -4 ACETIC 1.8 x 10 -5 FORMIC 1.8 x 10 -4 BENZOIC 6.0 x 10 -5 AS K a , ACID GETS WEAKER UNDEFINED INDICATES A VERY LARGE VALUE & ACID IS A STRONG ACID (100% DISSOCIATION) STRONG ACIDS WEAKEST ACID WEAK ACIDS *
  33. 33. CALCULATING HYDROGEN AND HYDROXIDE CONCENTRATIONS <ul><li>PURE WATER CONTAINS VERY SMALL CONCENTRATIONS OF BOTH HYDROGEN AND HYDROXIDE IONS. IN PURE WATER THE [H + ] = [OH - ] AND BOTH EQUAL 1.00 X 10 -7 MOLAR </li></ul><ul><li>USING THIS FACT THE EQUILIBRIUM CONSTANT (K w ) FOR THE DISSOCIATION OF PURE WATER INTO HYDROGEN AND HYDROXIDE ION CAN BE CALCULATED AS 1.00 x 10 -14 </li></ul><ul><li>H 2 O (l)  H + (aq) + OH - (aq) </li></ul><ul><li>K w = [H + ] x [OH - ] </li></ul><ul><li>(1.00 x 10 -7 )(1.00 x 10 -7 ) = 1.00 x 10 -14 </li></ul>*
  34. 34. PH OF A STRONG ACID <ul><li>WHAT IS THE PH OF 2.0 LITERS OF NITRIC ACID SOLUTION WHICH CONTAINS 15.75 GRAMS OF THE ACID? </li></ul><ul><li>SOLUTION: NITRIC ACID (HNO 3 ) IS A STRONG AND DISSOCIATES COMPLETELY . </li></ul><ul><li>HNO 3  H + + NO 3 - </li></ul><ul><li>THE MOLAR MASS OF HNO 3 IS 63.0 GRAMS </li></ul><ul><li>MOLES OF ACID = 15.75 GRAMS / 63.0 = 0.25 MOLES </li></ul><ul><li>[H + ] = 0.25 MOLES / 2.0 LITERS = 0.125 M </li></ul><ul><li>PH = - LOG [H + ] = - LOG (0.125) = 0.903 </li></ul>*
  35. 35. CALCULATING HYDROGEN AND HYDROXIDE CONCENTRATIONS (CONT’D) <ul><li>USING THE K w CONSTANT FOR THE DISSOCIATION OF PURE WATER WE CAN CALCULATE THE [H + ] IF THE [OH - ] IS KNOWN OR VISE VERSA. </li></ul><ul><li>FOR EXAMPLE: </li></ul><ul><li>WHAT IS THE CONCENTRATION OF HYDROGEN ION IN A SOLUTION WITH THE [OH - ] = 2.0 x 10 -5 M ? </li></ul><ul><li>K w = [H + ] x [OH - ] = 1.00 x 10 -14 </li></ul><ul><li>[H + ](2.00 x 10 -5 ) = 1.00 x 10 -14 , [H + ] = 5.00 x 10 -10 M </li></ul><ul><li>THE SOLUTION IS ACIDIC . </li></ul><ul><li>SOLUTIONS WITH [H + ] > 1.00 x 10 -7 M AND [OH - ] < 1.00 x 10 -7 M ARE ACIDIC. </li></ul><ul><li>SOLUTIONS WITH [H + ] < 1.00 x 10 -7 M AND [OH - ] > 1.00 x 10 -7 M ARE BASIC. </li></ul>*
  36. 36. PH OF WEAK ACIDS (CALCULATIONS USING K a ) <ul><li>FOR A WEAK ACID HX </li></ul><ul><li>HX (aq)  H + (aq) + X - (aq) </li></ul><ul><li>K a = [H + ] x [X - ] AND PH = -LOG [H + ] </li></ul><ul><li>[HX] </li></ul><ul><li>WHAT IS THE PH OF A 0.10 M SOLUTION OF ACETIC ACID (K a = 1.8 x 10 -5 ) ? </li></ul><ul><li>BASED ON THE BALANCED EQUATION FOR EVERY H + FORMED AN X - IS ALSO FORMED. </li></ul><ul><li>IF [H + ] = X THEN [X - ] = X AND [HX] = 0.10 - X </li></ul><ul><li>ADDITIONALLY IF K a IS VERY SMALL THEN THE ACID IS VERY WEAK AND [H + ] IS VERY SMALL THEREFORE 0.10 –X ~ 0.10 M </li></ul><ul><li>1.8 x 10 -5 = ( X 2 / 0.10) </li></ul><ul><li>[H + ] = X = ((1.8 x 10 -5 )(0.10)) 1/2 = 1.3 x 10 -3 M </li></ul><ul><li>PH = - LOG (1.3 x 10 -3 ) = 2.87 </li></ul>*
  37. 37. CALCULATIONS INVOLVING WEAK BASES <ul><li>THE PH OF A 0.10 M AMMONIA SOLUTION IS 11.37. WHAT IS THE K b FOR NH 3 ? </li></ul><ul><li>NH 3(aq) + H 2 O  NH 4 + (aq) + OH - (aq) </li></ul><ul><li>PH + POH =14.0, POH = 14.0 – 11.37 = 2.87 </li></ul><ul><li>K b = [NH 4 + ] x [OH - ] AND POH – LOG [OH - ] </li></ul><ul><li>[NH 3 ] </li></ul><ul><li>[OH - ] = 10 -2.87 = 1.35 x 10 -3 M, FROM THE EQUATION FOR EACH OH - ONE NH 4 + ALSO FORMS SO [NH 4 + ] = 1.35 x 10 -3 M AND [NH 3 ] = 0.10 – 1.35 x 10 -3 = .0986 </li></ul><ul><li>K b = ( 1.35 x 10 -3 ) 2 / (.0986) = 1.8 x 10 -5 </li></ul>*
  38. 38. TITRATION <ul><li>TITRATION REFERS TO THE ADDITION OF AN ACID AND BASE IN MEASURED QUANTITIES. OFTEN THE TITRATION IS CARRIED OUT TO AN END POINT. THE END POINT IS THE POINT WHERE THE MOLES OF ADDED ACID AND BASE ARE EQUAL. THE END POINT IS NOT ALWAYS THE NEUTRAL POINT </li></ul><ul><li>WHEN STRONG ACIDS ARE TITRATED WITH STRONG BASES TO THE END POINT A NEUTRAL SOLUTION RESULTS (PH =7.00) </li></ul><ul><li>WHEN STRONG ACIDS ARE TITRATED WITH WEAK BASES TO THE END POINT AN ACIDIC SOLUTION RESULTS (PH < 7.00) </li></ul><ul><li>WHEN STRONG BASES ARE TITRATED WITH STRONG BASES TO THE END POINT A BASIC SOLUTION RESULTS (PH > 7.00) </li></ul><ul><li>WHEN WEAK ACIDS AND BASES ARE TITRATED TO THE END POINT THE RELATIVE STRENGTHS OF EACH DETERMINES THE ACIDITY OF THE RESULTING SOLUTION. </li></ul>
  39. 39. TITRATION (CONT’D) STRONG ACID (HCl) STRONG BASE (KOH) WEAK ACID (HF) WEAK BASE (NH 3 ) NEUTRAL PH = 7.00 ACIDIC PH < 7.00 BASIC PH > 7.00 END POINT SOLUTIONS ACIDIC BASIC OR NEUTRAL
  40. 40. NORMALITY AND TITRATION <ul><li>NORMALITY IS A SYSTEM OF MEASURING THE CONCENTRATION OF SOLUTIONS WHICH IS OFTEN USED IN TITRATIONS. </li></ul><ul><li>THE NORMALITY OF AN ACID IS EQUAL TO THE MOLES OF HYDROGEN IONS AVAILABLE PER LITER OF SOLUTION. </li></ul><ul><li>THE NORMALITY OF A BASE IS EQUAL TO THE MOLES OF HYDROXIDE IONS AVAILABLE PER LITER OF SOLUTION. </li></ul><ul><li>N ACID = MOLES OF H + IONS / LITER </li></ul><ul><li>N BASE = MOLES OF OH - IONS / LITER </li></ul>*
  41. 41. NORMALITY AND TITRATION (CONT’D) <ul><li>A MOLE OF H + IONS OR OH - IONS IS CALLED AN EQUIVALENT. THEREFORE NORMALITY MAY BE DEFINED AS EQUIVALENTS PER LITER. </li></ul><ul><li>THE NORMALITY OF AN ACID CAN BE RELATED TO ITS MOLARITY BY THE NUMBER OF REPLACEABLE H + IONS CONTAINED IN THE ACID. </li></ul><ul><li>1 MOLAR HCl ~ 1 NORMAL HCl </li></ul><ul><li>1 MOLAR H 2 SO 4 ~ 2 NORMAL H 2 SO 4 </li></ul><ul><li>1 MOLAR H 3 PO 4 ~ 3 NORMAL H 3 PO 4 </li></ul>*
  42. 42. NORMALITY AND TITRATION (CONT’D) <ul><li>THE NORMALITY OF AN BASE CAN BE RELATED TO ITS MOLARITY BY THE NUMBER OF REPLACEABLE OH - IONS CONTAINED IN THE BASE </li></ul><ul><li>1 MOLAR NaOH ~ 1 NORMAL NaOH </li></ul><ul><li>1 MOLAR Ca(OH) 2 ~ 2 NORMAL Ca(OH) 2 </li></ul><ul><li>1MOLAR Al(OH) 3 ~ 3 NORMAL Al(OH) 3 </li></ul>*
  43. 43. TITRATION CALCULATIONS (STRONG ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HCl 0.10 M WITH 50 MLS OF NaOH 0.10 M. </li></ul><ul><li>SOLUTION: </li></ul><ul><li>MOLARITY x LITERS = MOLES </li></ul><ul><li>ACID (HCl) 0.10 x 0.100 = 0.0010 (H + ) </li></ul><ul><li>BASE (NaOH) 0.10 x 0.050 = - 0.0005 (OH - ) </li></ul><ul><li>H + (aq) + OH - (aq)  H 2 O (l) 0.005 EXTRA H + </li></ul><ul><li>[H + ] REMAINING = 0.005MOLES / (0.100 + 0.050) L </li></ul><ul><li>[H + ] = .033 M, PH = -LOG(0.033) = 1.48 </li></ul>
  44. 44. TITRATION CALCULATIONS (CONT’D) (STRONG ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HCl 0.10 M WITH 100 MLS OF NaOH 0.10 M. </li></ul><ul><li>SOLUTION: </li></ul><ul><li>MOLARITY x LITERS = MOLES </li></ul><ul><li>ACID (HCl) 0.10 x 0.100 = 0.0010 (H + ) </li></ul><ul><li>BASE (NaOH) 0.10 x 0.100 = - 0.0010 (OH - ) </li></ul><ul><li>H + (aq) + OH - (aq)  H 2 O (l) 0.00 EXTRA H + </li></ul><ul><li>WHEN MOLES OF H + = MOLES OF OH - THEN SOLUTION IS NEUTRAL AND THE PH MUST BE 7.00 </li></ul><ul><li>THIS IS TRUE FOR ALL STRONG ACID – STRONG BASE TITRATION END POINTS. </li></ul>
  45. 45. pH 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Equivalent point moles acid = moles base Titration of Strong Acid vs Strong Base Volume of Base Added Strong acid – strong base Titration equivalent point at pH = 7.00 0.10 M HCl + 0.10 M NaOH
  46. 46. TITRATION CALCULATIONS (WEAK ACID – STRONG BASE) <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HAc 0.10 M WITH 25 MLS OF NaOH 0.10 M.(Hac = HC 2 H 3 O 2 ACETIC ACID) </li></ul><ul><li>SOLUTION: EACH MOLE OF ADDED BASE CONSUMES A MOLE OF ACID AND FORMS A MOLE OF SALT (AC - ION) </li></ul><ul><li>MOLARITY x LITERS = MOLES </li></ul><ul><li>ACID (HAc) 0.10 x 0.100 = 0.0100 (HAc) </li></ul><ul><li>BASE (NaOH) 0.10 x 0.025 = - 0.0025 (OH - ) </li></ul><ul><li>H + (aq) + OH - (aq)  H 2 O (l) 0.0075 EXTRA HAc </li></ul><ul><li>[HAc] REMAINING = 0.0075 MOLES / (0.100 + 0.025) L </li></ul><ul><li>[HAc] = 0.006 M (A WEAK ACID) </li></ul><ul><li>MOLES SALT FORMED = MOLES OF BASE ADDED </li></ul><ul><li>[Ac - ] = MOLES SALT / LITER </li></ul><ul><li>[Ac - ] = 0.0025 MOLES / 0.125 L = 0.020 M </li></ul>*
  47. 47. TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) <ul><li>K a = 1.8 x 10 -5 , [H + ] = X </li></ul><ul><li>HAc  H + + Ac - , K a = ([H + ] x [Ac - ]) / [HAc] </li></ul><ul><li>[H + ] = K a x [HAc] = (1.8 x 10 -5 )(0.006) = 5.4 x10 -6 M </li></ul><ul><li>[Ac - ] 0.020 </li></ul><ul><li>PH = - LOG [H + ] = - LOG (5.4 x10 -6 ) = 5.26 </li></ul>*
  48. 48. <ul><li>FIND THE PH OF A SOLUTION OBTAINED BY MIXTURE 100 MLS OF HAc 0.10 M WITH 100 MLS OF NaOH 0.10 M.(Hac = HC 2 H 3 O 2 ACETIC ACID) </li></ul><ul><li>SOLUTION: EACH MOLE OF ADDED BASE CONSUMES A MOLE OF ACID AND FORMS A MOLE OF SALT (AC - ION) </li></ul><ul><li>MOLARITY x LITERS = MOLES </li></ul><ul><li>ACID (HAc) 0.10 x 0.100 = 0.0100 (HA </li></ul><ul><li>BASE (NaOH) 0.10 x 0.100 = - 0.0100 (OH - ) </li></ul><ul><li>H + (aq) + OH - (aq)  H 2 O (l) 0.00 EXTRA HAc </li></ul><ul><li>MOLES SALT FORMED = MOLES OF BASE ADDED </li></ul><ul><li>[Ac - ] = MOLES SALT / LITER </li></ul><ul><li>[Ac - ] = 0.0100 MOLES / 0.125 L = 0.080 M (ONLY A SALT SOLUTION REMAINS) </li></ul>TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) *
  49. 49. <ul><li>SINCE ONLY A SALT SOLUTION IS PRESENT THE QUESTION NOW BECOMES, “WHAT IS THE PH OF A 0.080 M SOLUTION OF NaAc ?” </li></ul><ul><li>NaAc  Na + + Ac - (ALKALI SALTS DISSOCIATE COMPLETELY) </li></ul><ul><li>Na + CAN ACT AS NEITHER ACID NOR BASE. IT CAN’T ACCEPT PROTONS (BOTH IT AND A PROTON ARE POSITIVE) AND IT HAS NO H + IONS TO LOSE. </li></ul><ul><li>Ac - CAN’T ACT AS AN ACID (IT HAS NO H + IONS) BUT BEING THE CONJUGATE BASE OF A WEAK ACID (ACETIC ACID) IT CAN ACCEPT PROTONS AND ACT AS A BASE. </li></ul><ul><li>Ac - + H 2 O  HAc + OH - (THE FORMATION OF HYDROXIDE ION MAKES THE SOLUTION BASIC) </li></ul><ul><li>THE SALT OF A WEAK ACID ANION AND A STRONG BASE CATION FORMS A BASIC SOLUTION. </li></ul>TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) *
  50. 50. TITRATION CALCULATIONS (CONT’D) (WEAK ACID – STRONG BASE) <ul><li>EQUATIONS: </li></ul><ul><li>(1) HAc + NaOH  NaAc + H 2 O </li></ul><ul><li>(2) NaAc  Na + + Ac - </li></ul><ul><li>(3) Ac - + H 2 O  HAc + OH - </li></ul><ul><li>K w = K a x K b , K b = K w / K a , K b = 1.0 x 10 -14 / 1.8 x 10 -5 </li></ul><ul><li>K b = 5.56 x 10 -10 = [HAc] x [OH - ] = X x X = X 2 </li></ul><ul><li>[Ac - ] 0.080 0.080 </li></ul><ul><li>X = [OH - ] = 6.67 x 10 -6 M, </li></ul><ul><li>POH = - LOG (6.67 x 10 -6 ) = 5.17, PH = 14.0 – POH </li></ul><ul><li>PH = 8.82 (BASIC SOLUTION) </li></ul>*
  51. 51. pH 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Equivalent point moles acid = moles base Titration of Weak Acid vs Strong Base Volume of Base Added Weak acid – strong base Titration equivalent point at pH > 7.00 Buffer region 0.10 M HAc + 0.10 M NaOH *
  52. 52. NORMALITY AND TITRATION (CONT’D) <ul><li>AT THE END POINT OF ACID – BASE TITRATION (ALSO CALLED EQUIVALENCE POINT), MOLES OF H + IONS ADDED FROM THE ACID EQUAL MOLES OF OH - IONS ADDED FROM THE BASE. </li></ul><ul><li>N ACID = MOLES H + / LITERS </li></ul><ul><li>MOLES H + = N ACID x LITERS </li></ul><ul><li>N BASE = MOLES OH - / LITERS </li></ul><ul><li>MOLES OH - = N BASE x LITERS </li></ul><ul><li>AT ENDPOINT MOLES H + = MOLES OH - </li></ul><ul><li>THEREFORE: N ACID x VOL ACID = N BASE x VOL BASE </li></ul>*
  53. 53. BUFFERS <ul><li>WHAT IS A BUFFER? </li></ul><ul><li>A WEAK ACID AND ITS SALT OR A WEAK BASE AND ITS SALT. </li></ul><ul><li>WHAT DOES A BUFFER DO? </li></ul><ul><li>A BUFFER SOLUTION RESISTS PH CHANGES WHEN SMALL QUANTITIES OF ACID OR BASE ARE ADDED. </li></ul><ul><li>HOW DO BUFFERS WORK? </li></ul><ul><li>THEY USE THE EQUILIBRIUM CONCEPTS DESCRIBED BY LE CHATELIER’S PRINCIPLE. </li></ul>
  54. 54. BUFFERS (CONT’D) <ul><li>LE CHATELIER’S PRINCIPLE STATED THAT A SYSTEM AT EQUILIBRIUM CONSUME ADDED REACTANTS OR PRODUCTS BY SHIFTING AWAY FROM THE ADDED COMPONENT AND WILL REPLACE REMOVED REACTANT OR PRODUCT BY SHIFTING TOWARDS THE REMOVED COMPONENT. </li></ul><ul><li>IN A BUFFER AN EQUILIBRIUM EXISTS BETWEEN A WEAK ACID , IT ANION AND THE HYDROGEN ION. </li></ul><ul><li>HAc  H + + Ac - </li></ul><ul><li>weak acid hydrogen ion acid anion (conjugate base) </li></ul><ul><li>ADDING ACID (H + ) WILL SHIFT THE SYSTEM LEFT THEREBY CONSUMING ADDED ACID ALONG WITH THE ANION (Ac - ) AND FORMING MORE WEAK ACID (HAc) </li></ul><ul><li>ADDING BASE (OH - ) WILL DECREASE H + ION CONCENTRATION AND SHIFT THE SYSTEM RIGHT CREATING REPLACEMENT H + IONS ALONG WITH Ac - IONS AND THEREBY CONSUME THE WEAK ACID (HAc) </li></ul>
  55. 55. BUFFERS (CONT’D) <ul><li>SUMMARY OF EFFECTS OF ADDING AN ACID TO AN ACIDIC BUFFER: </li></ul><ul><li>[WEAK ACID] , [CONJUGATE BASE] , SYSTEM SHIFTS LEFT (TOWARDS REACTANTS) </li></ul><ul><li>SUMMARY OF EFFECTS OF ADDING A BASE TO AN ACIDIC BUFFER: </li></ul><ul><li>[WEAK ACID] , [CONJUGATE BASE] , SYSTEM SHIFTS RIGHT (TOWARDS PRODUCTS) </li></ul><ul><li>ADDING ACID OR BASE TO A BASIC BUFFER (WEAK BASE AND ITS SALT) WILL HAVE EXACTLY THE OPPOSITE EFFECT ON THE WEAK BASE AND ITS CONJUGATE ACID (CATION). </li></ul>
  56. 56. BUFFERS (CONT’D) <ul><li>WHAT IS THE PH OF A BUFFER THAT CONSISTS OF 0.10 M HAc AND 0.05 M NaAc ? </li></ul><ul><li>HAc  H + + Ac - , K a = [H + ] x [Ac - ] </li></ul><ul><li>[HAc] </li></ul><ul><li>[SALT] = [Ac - ] = 0.05 M, [ACID WEAK] = [HAc] =0.10 M </li></ul><ul><li>[H + ] = K a x [HAc] = (1.8 x 10 -5 ) (0.10) = 3.6 x10 -5 M </li></ul><ul><li>[Ac - ] 0.05 </li></ul><ul><li>PH = - LOG (3.6 x10 -5 ) = 4.44 </li></ul>*
  57. 57. ADDING ACID TO AN UNBUFFERED SYSTEM <ul><li>HOW DOES THE PH OF A LITER OF WATER CHANGE WHEN 0.0001 MOLES OF HCl ARE ADDED? </li></ul><ul><li>SOLUTION: </li></ul><ul><li>PURE WATER HAS A PH = 7.00 </li></ul><ul><li>HCl IS A STRONG ACID (100% DISSOCIATION) </li></ul><ul><li>HCl  H + + Cl - , [H + ] = 0.0001 MOLES / 1.0 LITER </li></ul><ul><li>PH = - LOG (0.0001) = 4.00 </li></ul><ul><li>THE CHANGE IN PH IS FROM 7.00 TO 4.00 OR 3.00 PH UNITS. THIS CHANGE MEANS THE SYSTEM HAS BECOME 1000 TIMES MORE ACIDIC (10 3 = 1000) </li></ul>*
  58. 58. ADDING ACID TO AN BUFFERED SYSTEM <ul><li>HOW DOES THE PH OF A LITER OF A BUFFER COMPOSED OF 0.10 M HAc AND 0.05 M NaAc CHANGE WHEN 0.0001 MOLES OF HCl ARE ADDED? </li></ul><ul><li>SOLUTION: </li></ul><ul><li>HAc  H + + Ac - , ADDING AN ACID SHIFTS THE SYSTEM TO THE LEFT. </li></ul><ul><li>MOLARITY x LITERS = MOLE (ORIGINAL MOLES) </li></ul><ul><li>0.10 x 1.0 = 0.10 MOLES OF HAc </li></ul><ul><li>0.05 x 1.0 = 0.05 MOLES NaAc (Ac - ) </li></ul><ul><li>WHEN EQUILIBRIUM SHIFTS THE MOLES OF HAc WILL INCREASE BY THE NUMBER OF MOLES OF ADDED ACID AND MOLES OF Ac - WILL DECREASE BY THE NUMBER OF MOLES OF ADDED ACID. </li></ul><ul><li>THEREFORE AT EQUILIBRIUM: </li></ul><ul><li>MOLES OF HAc =0.10 + 0.0001 = 0.1001 </li></ul><ul><li>MOLES OF Ac - = 0.05 – 0.0001 = 0.0499 </li></ul>*
  59. 59. ADDING ACID TO AN UNBUFFERED SYSTEM <ul><li>[HAc] eq = 0.1001 MOLES / 1 LITER = 0.1001 M </li></ul><ul><li>[Ac - ] eq = 0.0499 MOLES / 1 LITER = 0.0499 M </li></ul><ul><li>[H + ] eq = X </li></ul><ul><li>K a = [H + ] x [Ac - ] , [H + ] = K a x [HAc] </li></ul><ul><li>[HAc] [Ac - ] </li></ul><ul><li>[H + ] = (1.8 x 10 -5 ) (0.1001) = 3.61 x10 -5 M </li></ul><ul><li>0.0499 </li></ul><ul><li>PH = 4.442, PH OF THE ORGINAL BUFFER PREVIOUSLY CALCULATED = 4.444 </li></ul><ul><li>THE PH OF THE BUFFERED SOLUTION HARDLY CHANGES WITH THE ADDED ACID WHILE WHEN THE SAME QUANTITY OF ACID IS ADDED TO PLAIN WATER THE PH CHANGES DRAMATICALLY. A BUFFER STABILIZES PH . </li></ul>*
  60. 60. THE END
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