of chemicals

of chemicals

plating

Contents• How is it related to syllabus in ‘O’ Levels

• History

• What is electroplating?

• Application

• Lab experiment

• Harmful effects of electroplating through process and nature of chemicals

‘O’ Level Syllabus

• Under the topic on electrolysis, students should be able to describe the electroplating of metals, e.g. copper plating, and state one use of electroplating

A new era of electrochemistry started when Humphry Davy (1778–1829), a British chemist, built a powerful battery to pass electricity through molten salts. He discovered elements, such as potassium, sodium, calcium and magnesium, by liberating them from their molten compounds.

But who actually invented

electroplating?

Who was smart enough to have came up with the theory of

ELECTROPLATING?• Italian chemist, Luigi Brugnatelli

• Invented electroplating in 1805

• Brugnatelli performed electrodeposition of gold using the Voltaic Pile

• His work was rebuffed by the dictator Napoleon Bonaparte

• He still did write about electroplating in the Belgian Journal of Physics and Chemistry

What is ELECTROPLATIN

G?Electroplating is the deposition of a metallic coating by putting a negative charge on an object and exposing it to a solution containing a metal salt. The positively charged metal ions in the salt solution are attracted to the object and reduced to metallic form upon it.

Putting ELECTROPLATING into APPLICATION1. Rust protection

2.Acid/Alkali protection3.Volt increase in

conductivity

4. Jewellery making

5. Lead protection

Theory of ELECTROPLATINGAnode - connected to the positive terminal of the battery

Cathode - connected to the negative terminal of the battery

Lemmon battery

When power is switched on:

• Copper is oxidized at the anode to Cu2+ by losing 2 electrons

• Cu 2+ associates with SO42- in the

solution to form CuSO4

• Cu2+ is reduced to metallic Cu at the cathode by gaining 2 electrons

Redox reaction occurs during electroplating.

Why is the object to be plated placed at the cathode?

• It is because the cathode is

negatively charged by being connected to the negative terminal of the battery.

Hence, the Cu2+ ions are

attracted to the object at the cathode.

Cu2+

Copper (anode)

Coin (cathode)

Time to conduct a

little EXPERIMENT

!

PROCEDURES1. 200ml of the electrolyte solution is poured into a beaker

2. Wires with alligator clips are connected to the terminals of the power supply.

3. The coins are cleaned with a mixture of 3g NaCl and 15ml vinegar, rinsed and dried.

4. One end of a 10-cm length of copper is tightly wrapped around each coin, leaving 5-6 cm of wire free.

5. The mass of each coin-copper wire is measured and recorded

6. The set up is prepared as shown.

7. The electroplating cell is allowed to operated for 60 minutes.

8. The electrode is being removed and dried, being careful not to lose any of the copper plating.

9. The mass of the end product is measured and recorded.

Mass before electroplating / g 1.4g

Mass after electroplating / g

1.6g

RESULTS

1.6g – 1.4g = 0.2g of copper was coated on the coin.

ConclusionEffective transfer of copper from

anode source to a plate covering the cathode.Copper, Nickel, Silver, Gold, Chromium } single metallic elements

Brass, Solder } alloys

As reported in ‘Guidelines For The Safe Use Of Chemicals In Electroplating’, the nature of chemicals used in electroplating

processes are toxic and corrosive to the skin. It is important that everyone could potentially come into contact with the chemicals should know and understand the risks involved and the specific handling precautions required for each chemical. In addition,

protective equipments and clothings need to be worn.

Is it harmful?

Hydrochloric acidPhysical

stateStorage Use

Possible biological effects

•Pungent •Fuming•Yellow liquid

• Acid store • Acid dips• Electroplating solutions

•May produce burns•Irritation to Mucous membranes, skin, eyes•Higher concentrations may cause Laryngitis,•Bronchitis, Pulmonary oedema

Physical state

Storage UsePossible biological effects

•Green solid • Dry store• Nickel electroplating

•Upper respiratory tract irritation•Eye irritation•Skin sensitisation, nickel itch resembling allergic•Dermatitis or irritant dermatitis.

Nickel salts chlorides, sulfate

Physical state

Storage UsePossible biological effects

•Clear to yellow liquid

• Acid store

• Surface activation •Pickling •Chrome and copper Electroplating•Anodising

•Respiratory tract irritation•Eye irritation•Contact with the skin or eyes may produce burns•Long term effects of bronchitis

Sulfuric acid

Special THANKS to the following websites• http://www.osh.dol.govt.nz/order/catalogue/pdf/electroplating.pdf

• http://sg.images.search.yahoo.com/search/images?ei=UTF-8&p=Trichloroethylene&y=Search&fr2=tab-web&fr=yfp-t-web-s

• http://www.enviroliteracy.org/images/page-spec/sulfuric%20acid.gif• http://www3.moe.edu.sg/edsoftware/ir/files/chem-titration-setup/images/hydr

ochloric_acid_3835.jpg• http://penelopeillustration.com/blog/wp-content/backgrounds.jpg• http://inventors.about.com/od/estartinventions/a/Electroplating.htm• http://www.finishing.com/faqs/howworks.html• http://www.lwkoo.cn/Freepaper/UploadFiles_2179/200809/20080904151421

43.jpg• http://savetherobot.files.wordpress.com/2009/01/the-end.jpg• http://www.woodrow.org/teachers/chemistry/institutes/1986/exp30.html• http://www.fotosearch.com.au/clip-art/good.html• http://www.fotosearch.com.au/clip-art/coin.html• www.fotosearch.com.au• www.google.com• www.yahoo.com• www.wikipedia.com• http://www.wondercliparts.com/hugs/graphics/hugs_graphics_04.gif

A big thank you to our fellow teachers

for their wisdom, the School for its endless support, the textbook for

providing valuable information and

any other person that has helped in

one way or another.