The Breathalyser Reaction C 2 H 2 OH+ Cr 2 O 7 2- → CH 3 COOH+Cr 3+

The Breathalyser Reaction

C2H2OH + Cr2O7

2- → CH3COOH + Cr3+

Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance OxidizedSubstance ReducedReducing AgentOxidizing Agent

The Breathalyser ReactionLook at the oxidation numbers!-0.5 +6 0 +3

C2H2OH + Cr2O72- → CH3COOH + Cr3+

Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance OxidizedSubstance ReducedReducing AgentOxidizing Agent



Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance Oxidized C2H2OH Substance ReducedReducing AgentOxidizing Agent



Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance Oxidized C2H2OH Substance ReducedReducing Agent C2H2OH Oxidizing Agent



Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance Oxidized C2H2OH Substance Reduced Cr2O7

2-

Reducing Agent C2H2OH Oxidizing Agent



Ethanol Orange Acetic Acid Green If the orange colour decreases there is alcohol present. It is measured with a spectrophotometer. The more it decreases, the higher the blood alcohol content. Legal Limit Class 5 Licence 0.08 mg/mLLegal Limit New Driver 0.00 mg/mL Substance Oxidized C2H2OH Substance Reduced Cr2O7

2-

Reducing Agent C2H2OH Oxidizing Agent Cr2O7

2-

Balance in acid solution

C2H2OH + Cr2O7



C2H2OH + Cr2O7


Cr2O72- → Cr3+

C2H2OH → CH3COOH


C2H2OH + Cr2O7


Cr2O72- → 2Cr3+

C2H2OH → CH3COOH


C2H2OH + Cr2O7


Cr2O72- → 2Cr3+ + 7H2O

C2H2OH + H2O → CH3COOH


C2H2OH + Cr2O7


14H+ + Cr2O72- + → 2Cr3+ + 7H2O

C2H2OH + H2O → CH3COOH + H+


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O

C2H2OH + H2O → CH3COOH + H+ + 1e-


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O

6(C2H2OH + H2O→ CH3COOH+ H+ + 1e-)


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O


14H+ + Cr2O72- + 6C2H2OH + 6H2O → 2Cr3++7H2O+6CH3COOH+6H+


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O


8 114H+ + Cr2O7

2- + 6C2H2OH + 6H2O → 2Cr3++7H2O+6CH3COOH+6H+


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O


8H+ + Cr2O72- + 6C2H2OH → 2Cr3+ + 1H2O + 6CH3COOH


C2H2OH + Cr2O7


14H+ + Cr2O72- + 6e- → 2Cr3+ + 7H2O



+6 +6

Balance in base solution




8OH- 8OH-



8OH- 8H2O 8OH-


Cr2O72- + 6C2H2OH → 2Cr3 + 1H2O + 6CH3COOH + 8OH-

7 8H2O


7H2O + Cr2O72- + 6C2H2OH → 2Cr3+ + 6CH3COOH + 8OH-

Review of Cells

Electrochemical Electrolytic Is a power supply Requires power supplySpontaneous (+ ve) Nonspontaneous(-ve)Makes electricity Makes chemicals Reduction is highest on Chart Reduction is the –ve

For all cells:

Cations migrate to the cathode, which is the site of reduction. Anions migrate to the anode, which is the site of oxidation. Electrons travel through the wire from anode to cathode.

Complete the Chart Electrochemical Cell: Zn, Zn(NO3)2 II Cu, CuSO4

Anode: Reaction:

Cathode: Reaction:

E0 =


Anode: Zn Reaction:

Cathode: Cu Reaction:

E0 =

Higher on reduction Chart


Anode: Zn Reaction: Zn → Zn2+ + 2e- 0.76 v

Cathode: Cu Reaction:

E0 =

Higher on reduction Chart


Anode: Zn Reaction: Zn(s) → Zn2+ + 2e- 0.76 v

Cathode: Cu Reaction: Cu2+ + 2e- → Cu(s) 0.34 v

E0 = Higher on reduction Chart


Anode: Zn Reaction: Zn → Zn2+ + 2e- 0.76 v

Cathode: Cu Reaction: Cu2+ + 2e- → Cu(s) 0.34 v

E0 = 1.10 v Higher on reduction Chart

Electrolytic Cell: Molten AlCl3

Anode: Reaction: Cathode: Reaction:

Electrolytic Cell: Molten AlCl3 Al3+ Cl-

Anode: C Reaction: Cathode: C Reaction:


Anode: C Reaction: Cathode: C Reaction:

Put the vowels together: AnodeAnionOxidation


Anode: C Reaction: 2Cl- → Cl2 + 2e- -1.36 v Cathode: C Reaction:

Put the vowels together: AnodeAnionOxidation

Oxidation of Anion


Anode: C Reaction: 2Cl- → Cl2 + 2e- -1.36 v Cathode: C Reaction:

Put the consonants together: CathodeCationReduction


Anode: C Reaction: 2Cl- → Cl2 + 2e- -1.36 v Cathode: C Reaction: Al3+ + 3e- → Al -1.66 v

Put the consonants together: CathodeCationReduction

Reduction of Cation


Anode: C Reaction: 2Cl- → Cl2 + 2e- -1.36 v Cathode: C Reaction: Al3+ + 3e- → Al -1.66 v E0 = -3.02 v


Anode: C Reaction: 2Cl- → Cl2 + 2e- -1.36 v Cathode: C Reaction: Al3+ + 3e- → Al -1.66 v E0 = -3.02 v MTV = +3.02 v

Electrolytic Cell: KBr(aq)

Anode: Cathode:

Electrolytic Cell: KBr(aq) K+ Br- H2O

Anode: C Cathode: C

Electrolytic Cell: KBr(aq) K+ Br- H2O

Anode: C Cathode: C

Put the vowels together: AnodeAnion or waterOxidation


Anode: C 2Br- → Br2 + 2e- -1.09 v Cathode: C

Oxidation of Anion or WaterTake Lower one!


Anode: C 2Br- → Br2 + 2e- -1.09 v Cathode: C

Put the consonants together: CathodeCation or waterReduction



Anode: C 2Br- → Br2 + 2e- -1.09 v Cathode: C 2H2O + 2e- → H2 + 2OH- -0.41 v

Put the consonants together: CathodeCation or waterReduction


Reduction of Cation or WaterTake Higher one!


Anode: C 2Br- → Br2 + 2e- -1.09 v Cathode: C 2H2O + 2e- → H2 + 2OH- -0.41 v E0 = -1.50 v




Anode: C 2Br- → Br2 + 2e- -1.09 v Cathode: C 2H2O + 2e- → H2 + 2OH- -0.41 v E0 = -1.50 v MTV = +1.50 v



Electrochemical Cell: Ag, AgNO3 II Sn, Sn(NO3)2

Cathode: Anode:


*higher

Cathode: Ag Anode:


*higher

Cathode: Ag Ag+ + e- → Ag(s) +0.80 v Anode:


*higher

Cathode: Ag Ag+ + e- → Ag(s) +0.80 v Anode: Sn


*higher

Cathode: Ag Ag+ + e- → Ag(s) +0.80 v Anode: Sn Sn → Sn2+ + 2e- +0.14 v


*higher

Cathode: Ag 2(Ag+ + e- → Ag(s)) +0.80 v Anode: Sn Sn → Sn2+ + 2e- +0.14 v 2Ag+ + Sn → Sn2+ + 2Ag(s) E0 = 0.94 v

The Breathalyser Reaction C 2 H 2 OH+ Cr 2 O 7 2- → CH 3 COOH+Cr 3+

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Transcript of The Breathalyser Reaction C 2 H 2 OH+ Cr 2 O 7 2- → CH 3 COOH+Cr 3+