5.0 Chemical Reactions

Transcription

1 Acids & Bases Prof. Dr. Sabine Prys Acids Bases Chemical Equilibrium p Indicators by ps 5.0 Chemical Reactions redox reaction photo reaction surface reaction (e.g. catalysis) polymer reaction complex reaction chain reaction starting material Educts final material Products 1 1 C 1 C stochiometrical yields Seite 1

2 5.1 Semiconductor Etching etching: complexation: total: Si 4 N Si 4 N Si F SiF6 Si [ Si( ) 6 Si 4 N 9 F SiF6 4 N Acids Arrhenius : an acid is a material that donates a proton in ueous environment Cl Cl Brönsted : Every ion dissociation that involves a hydrogen could be considered an acid reaction Lewis : Acids are electron pair acceptors Cl colour change litmus neutral: violet acidic: red Seite

3 6.1 Cl Electronic Structure Cl Cl Cl: s p 5 : s 1 ation Anion 6. Properties of Acids 1 Acids corrode active metals Zn Cl Zn Cl strong acids highly dissociated Cl, S 4, ca. 80 % Cl weak acids slightly dissociated S, C ca < 1 % C Cl Cl Acids neutralize bases in a neutralization reaction. An acid and a base combine to make a salt and water Cl Na NaCl Seite

4 6. Properties of Acids Acids taste sour equilibrium reactions Cl Cl acidic solutions are electrolytes etching properties skin irritants Non oxygen containing acids nonmetal hydride acid hydrochloric acid Cl hydro sulphuric acid S oxygen containing acids nonmetal oxide acid sulphuric acid S 4 nitric acid N metal oxide acid Mn 7 Mn Bases Arrhenius : a base is a material that donates hydroxide ions in ueous environment Brönsted : Every ion dissociation that involves a hydroxide ion could be considered a base reaction Lewis : Bases are electron pair donators Na Na Na colour change litmus neutral: violet alkaline: blue Seite 4

5 7.1 Properties of Bases Bases denature protein bases taste bitter strong bases highly dissociated Ba, Na Ba(), Ba Na Na weak bases slightly dissociated N, N N 4 Bases metal hydroxides corrosive metal 0 metal hydroxide Na Na ½ metal oxide 0 metal hydroxide Ba Ba other properties: alkaline solutions are electrolytes, etching properties, skin irritants Test 1 Is N an acid or a base? N N N 4 N: s p : s 1 Seite 5

6 8.0 Equilibrium Constant 1 aa (reversible) chemical reaction bb k k k k [ C [ A c cc a [ D [ B dd d b [A,[B reactant concentration a,b mols of corresponding reactants [C,[D product concentration c,d mols of corresponding products k velocity of reaction k velocity of back reaction equilibrium constant 8.1 Equilibrium Constant (reversible) chemical reaction x B x ν B B x equilibrium constant x B equilibrium value either of pressure, fugacity, amount concentration, amount fraction, molality, relative activity or reciprocal absolute activity defining the pressure based, fugacity based, concentration based, amount fraction based, molality based, relative activity based or standard equilibrium constant ν B stoichiometric number of a reactant (negative) or product (positive) Seite 6

7 8.1.1 Reaction Velocity k aa bb cc dd k velocity of reaction d[ B dt d[ A dt k [ A 1 st order kinetics 8.1. Law of Mass Action aa bb µ µ µ µ [ C [ A c cc a [ D [ B dd d b chemical potential of reaction ( ) chemical potential of back reaction ( ) equilibrium constant depends on temperature chemical equilibrium: concentrations are not independent Seite 7

8 8.1. Chemical Potential 8. Acid Dissociation Constants A S p [ [ A S [ A [ [ [ [ A log S [ A A acid Strong acids S large p S little p S C 4,76 P 4,16 P 4 7,1 P 4 1, Seite 8

9 8. Base Dissociation Constants B B p [ B [ B [ B [ [ [ B [ log B B [ B Base strong base: B large p B little p B C 9,4 P 4 11,84 P 4 6,79 P 4 1,68 8. Deprotonation (Dissociation) Acid Protolysis [ [ α α [ A 0 Base Protolysis [ B 0 Deprotonation 1 M Solutions at 18 C N 8 % Cl 78 % C 0,4 % 77 % Na 7 % Seite 9

10 9.0 pvalues ampholytic behaviour: neutral water T 5 C: [ [ 10 7 mol / l Ion product of water: [ x [ mol / l pvalue: p log [ p log [ p p 14 neutral water [ 10 7 mol / l p 7 acidic water [ 10 mol / l p alkaline water [ mol / l p 10 p Exercises 1 What is the p of the following solutions? 10 m Cl p 10 1 m Cl p 1 0, m Cl p 0,5 1 m Cl p 0 Seite 10

11 p Exercises What is the p of the following solutions? [ x [ mol / l p p m Na p m Na p 1 0, m Na p 1,47 1 m Na p pexamples Lemon Juice Stomach Acid Coffee Battery Acid Lemonade Pure Water Laundry Detergent Solution Intestinal Liquid Vinegar Apple Juice Milk See Water Ammonia Solution Acidic Milk Potassium Bicarbonate Solution Seite 11

12 9.1 Strong and Weak Acids strong acids weak acids [ [ A p p s [ p [ A 1 [ A ( p log[ A ) 0 [ A s Weak Acid vs. Strong Acid ps C 4,76 1 m C p 0,5 * (4,76 0),8 1 m Cl p 0 ps C 4,76 10 m C p 0,5 * (4,76 ),88 10 m Cl p Seite 1

13 9. Strong and Weak Bases strong bases [ B [ p p B [ B 0 weak bases [ B p [ 1 [ B ( p log[ B ) B Weak Base vs. Strong Base p B P 4 11,84 p B P 4 11,84 1 m P 4 10 m P 4 p 0,5 * (11,84 0) 5,9 p 0,5 * (11,84 ) 7,4 1 m Na 10 m Na p 14 p 11 Seite 1

14 9. Corresponding Acids and Bases N N ACID BASE CNJUGATE BASE CNJUGATE ACID 9..1 Corresponding Acid/ Base Examples strong acid week base Cl hydrochloric acid S 4 sulfuric acid 1 oxonium ion S 4 sulfuric acid F hydrofluoric acid N 4 ammonium ion water Chlorine ion Cl sulfuric acid S 4 water sulfuric acid S 4 fluorine ion F ammonia N hydroxyl ion decreasing strength increasing strength Seite 14

15 9.. Corresponding Acid/Base Equilibrium A A S B S p S [ [ A [ A [ A [ [ A [ [ B p B 14 A A 14 mol 10 l 10.0 p Indicators Indicator acidic neutral alcaline Litmus red violet blue Thymol blue red yellow blue Methyl orange red yellow Methyl red red yellow Thymol phtalein colourless blue Phenol phtalein colourless pink C C Phenol phtalein Na Na C Na C Seite 15

16 10.1 p Indicator Table Methyl range Seite 16

17 11.0 Titration strong acid strong base weak acid strong base strong acid weak base Equivalence point neutral point Equivalence point > neutral point Equivalence point < neutral point Exercise: Titration Experiment 1 M Na 5, ml against 10 ml Cl What is the molarity of Cl? moles Na 0,1 moles Cl 0,1 [Cl 0,001 M Seite 17

18 Seite 18 [ [ 4,65, [ [ 0,4 1,0,1 [1.. [ [ p Puffer S C C S C C l mol l B z C CNa CNa C C C α 1 st result 1.0 Chemical Buffers Puffer S Cl Puffer S p p l mol l mol C C C Cl Cl l mol ml Cl C C CNa l mol l CNa C C C,,, ,56 0,1 0,01 [0,1 [ 1, [10 [ [ [ 0,4,0,1 [1 α nd result 1.1 Buffer Acid

19 1. Blood Buffer Pulmonary System C Veins Erythrocyte b b Arterials b b Erythrocyte C C p 7,4 0,5 Buffer: C 4 mmol.l 1 Protein mmol.l 1 P 4 mmol.l 1 Cells C Exercises 1. What is a LEWIS base?. What is a LEWIS acid?. Is water acidic or basic 4. What is the p of a o.ooo1 m Cl (Na)? 5. What is a corresponding base to P 4? 6. What is an appropriate indicator for Na? 7. Explain chemical buffers Seite 19

20 Exercises 1. What is the molecular weight of CuS 4 x 5?. ow many atoms are in 1 g Uranium?. ow much C must be oxidized to gain 10 6 t C? 4. Explain the formation of Si from Si and using oxidation numbers! 5. What are the oxidation numbers in SiCl? 6. ow do you prepare a 0.5 m solution of sodium chloride? 7. What is decantation? 8. What is extraction? Web Links Seite 0

21 References A. Burrows, A. Parsons, G. Price, J. olman, G. Pilling; Chemistry: Introducing inorganic, organic and physical chemistry ; xford University Press 009 J. oinkins; E. Lindner; Chemie für Ingenieure; Verlag: WileyV Verlag Gmb & Co. GaA, 007 P.W. Attkins; L. Jobnes; Chemie einfach alles; Verlag: WileyV Verlag Gmb & Co. GaA, 006 Römpp s Chemie Lexikon DTVAtlas zur Chemie Further keys Chemical Equilibrium Adsorption Crystallization Decantation Distillation Drying Evaporation Extraction Filtration Precipitation Recrystallisation Volatility Seite 1