lesson 08: the electrochemical cell · lesson 11: applied electrochemistry 01 drinking and driving...

Chemistry 12, Electrochemistry, Lesson 11, R. Janssen, 8/3/2016 1

Lesson 11: Applied Electrochemistry

01 Drinking and Driving and the Law: The Breathalyzer

RCMP Sobriety Road Check

Hand Held Breathalyzer


The breathalyzer is a law enforcement device for estimating blood alcohol (ethanol) content from a breath sample. Breath analyzers estimate blood alcohol content indirectly by measuring the amount of alcohol in one's breath. The breathalyzer contains:

a system to sample the breath of the suspect,

two glass vials containing the chemical reaction mixture,

a system of photocells connected to a device to measure the color change associated with the chemical reaction

Chemical Reaction

cathode - + 2- 3+2 7 26e +14H +Cr O 2Cr +7H O

anode + -

2 5 2 3C H OH+H O CH COOH+4H +4e

overall reaction

- + 2- 3+2 7 2

+ -2 5 2 3

+2 5

3

22 7

23

-

+

2(6e +14H +Cr O 2Cr +7H O)

3(C H OH+H O CH COOH+4H +4e )

16H +3C H OH+2

3CH

Cr O

COOH+4 +1C 1Hr O


Progressive Effects of Alcohol

BAC (%) Behaviour Impairment

0.01–0.029 Average individual appears normal

Subtle effects that can be detected with special tests

0.03–0.059 Mild euphoria Sense of well-being Relaxation Talkativeness Joyous Decreased inhibition

Alertness Judgment Coordination Concentration

0.06–0.10 Blunted feelings Loss of inhibition Extroversion Impaired sexual pleasure

Reflexes Reasoning Depth perception Distance acuity Peripheral vision Glare recovery

0.11–0.20 Over-expression Emotional swings Angry or sad Boisterous

Reaction time Gross motor control Staggering Slurred speech

0.21–0.29 Stupor Loss of understanding Impaired sensations

Severe motor Impairment Loss of consciousness Memory blackout

0.30–0.39 Severe depression Unconsciousness Death possible

Bladder function Breathing Heart rate

>0.40 Unconsciousness Death

Breathing Heart rate


Charges for Drinking and Driving in British Columbia?

You risk three serious criminal charges if you drink and drive:

impaired driving (caused by alcohol or drugs – both legal prescription drugs and illegal ones)

driving with a blood-alcohol level over 50 milligrams (called “over 0.05”)

failing or refusing to provide breath or blood samples on demand (called “refusing to blow”)

Penalties?

For a first offence of over 0.05 impaired driving, or refusing to blow, the mandatory minimum sentence is a $600 fine and a one-year driving prohibition. That is the usual sentence, unless the judge considers your case more serious because of aggravating facts such as high breathalyzer readings or an accident. Previous drinking and driving convictions mean higher penalties. And if you kill or injure someone by drinking and driving, you will get higher penalties and risk being sued for a lot of money. The penalty for killing someone while impaired or over 0.05 is always a jail term. A conviction will also mean you have to pay much higher vehicle insurance premiums or possibly even lose your insurance coverage.


Driver Trips During a Police Sobriety Test

Watch Video: Sobriety Test Gone Wrong

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02 Batteries

Lead-Acid Batteries

In 1859, the French physicist Gaston Planté (1834-1889) invented a device, which, with minor design changes, is still used today as the car battery. It is an example of a secondary electrochemical cell, since it can be recharged. The lead-acid battery consists of 6 cells connected in series, each cell having an EMF (electromotive force) of about 2 V, giving 12 V as the overall EMF of the battery.


During the manufacturing process, initially the electrodes are

filled with litharge (PbO ), and immersed in the 2 4H SO

electrolyte (6M). When an electric current is passed through the battery, the negative electrode is converted to lead, while

the positive electrode is converted to 2PbO . There is no net

change in the concentration of acid. This process is called “forming the battery”.

Initial Charge Reactions

anode 2 2PbO(s) H O(l) PbO (s) 2H 2e

cathode 2PbO(s) 2e 2H Pb(s) H O(l)

overall

2

2 2

2

PbO(s) 2e 2H Pb(s) H O(l)

PbO(s) H O(l) PbO (s) 2H 2e

PbO(s) PbO(s) Pb(s) PbO (s)

When the battery is fully charged, the anode consists of metallic lead in a spongy form, while the cathode consists of lead dioxide. The electrolyte is an aqueous solution of sulphuric acid, at a concentration of approximately 6M.


As the battery provides energy, it is discharged and this leads to the gradual formation of lead sulphate at the electrodes, and a steady decrease in the concentration of the sulphuric acid.

Supplying Current Reactions

anode 4 4Pb(s) HSO PbSO (s) H 2e

cathode 2 4 4 2PbO (s) HSO 3H 2e PbSO (s) 2H O(l)

overall

-4 4

2 4 4 2

+ -2 4

4 2

Pb(s) HSO PbSO (s) H 2e

PbO (s) HSO 3H 2e PbSO (s) 2H O

Pb(s)+PbO (s)+2H +2HSO

2PbSO (s)+2H O(l)

4 2 2Pb Pb Pb Pb

If the battery is totally discharged, both electrodes will have been converted to lead sulphate. It will no longer be able to provide a current, and cannot be recharged. It is only good for the scrap-heap.


When the battery is being charged, (using a battery charger or engine alternator), electrons are supplied to the anode of the battery and this converts the lead sulphate to lead. At the same time, the lead sulphate at the anode is converted to lead dioxide.


Zinc-Carbon Battery / Dry Cell Battery

The dry cell, invented in 1867 by the French engineer Georges Leclanché (1839 - 1889), is widely used as a source of electric energy in flashlights and small appliances such as radios. The top of the battery is closed with a non-conducting sealing material. The cathode consists of a carbon rod tipped with a metal contact, which serves as the positive pole of the battery. The anode is a cylindrical zinc casing. The battery is filled with powdered manganese dioxide ( 2MnO ) and carbon powder (to

increase conductivity) and a moist paste of ammonium

chloride ( 4NH Cl) and zinc chloride (ZnCl). These two salts

serve as electrolytes. The EMF of the battery is about 1.5 V.


Inside the Zinc-Carbon Battery / Dry Cell Battery

Chemical Reactions

anode 2Zn Zn 2e

cathode 2 2 3 22MnO (s) 2H (aq) 2e Mn O (s) H O

acid source for cathode 4 3NH (aq) H (aq) NH (aq)

overall

2 2 3 2

2

2 4

2

2 3 3 2

2MnO (s) 2H (aq) 2e Mn O (s) H O

Zn Zn 2e

Zn(s) 2MnO (s) 2NH (aq)

Mn O (s) Zn NH (s)


03 Fuel Cells

Fuel Cell Vehicle

A fuel cell vehicle is a type of electric vehicle which uses a fuel cell to produce electricity, powering its on-board electric motor. Fuel cells in vehicles create electricity to power an electric motor using hydrogen (produced in one of several ways) and oxygen from the air. The diagram below shows the basic design of a fuel cell. In practice, it is a very complex piece of equipment, as shown in the picture at the bottom.


Fuel Cell in Detail

Chemical Reactions

anode 2H (g) 2H (aq) 2e

cathode 2 2O (g) 4e 4H (aq) 2H O(l)

overall

2 2

2

2 2 2

O (g) 4e 4H (aq) 2H O(l)

2(H (g) 2H (aq) 2e )

2H (g) O (g) 2H O(l)


Can you think of any societal implications around the use of the fuel cell?

Watch Video: Ballard Power Systems (3.5 minutes)

Watch Video: GVTV: Fuel Cells (5 minutes)

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../../../../../../../../Videos/Teaching%20Videos/Earth,%20Space%20and%20Environmental%20Science/All%20Subjects/Media%20-%20Canada/GVTV%20-%20Livable%20Regions%20Series/06%20fuel%20cells.wmv

lesson 08: the electrochemical cell · lesson 11: applied electrochemistry 01 drinking and driving...

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