Zinc

 

Zinc

Chemical formula	Zn
Atomic Number	30
OTP appearance	silver solid
Molar Mass(g/mol)	65.4
Density(g/cc)	6.57
Melting Point(°C)	419.5
Boiling Point(°C)	907
NFPA 704	0 2 0 W

Uses

Primary

• Essential element in brass
• Essential element for galvanizing steel
• Essential for multiple battery technologies

Secondary

• Sacrificial anode for boats
• -oxide as a skin protectant / cosmetic

Hazards

• Zinc and many of its compounds are toxic

Natural Sources

• Elemental zinc does occur naturally, but is exceedingly rare.
• The primary ores of zinc are hemimorphite, smithsonite, and sphalerite
• Nutritive zinc (sulfate, oxide, citrate, or ascorbate) is found in pumpkin, watermelon, and squash seeds.

Production

Extraction

India

1. Gather two ceramic, one with a male and one with a female stem
2. Place finely ground zinc ore in the male flask
3. Place coarse charcoal in the male flask atop the zinc oxide
4. (optional) place a small ceramic grate or porous plug in the male neck
5. Join the male and female necks
6. Arrange the flasks so that the male is above the female
7. Heat the male flask to red heat while keeping the female flask cool

   ZnO + C

   {

   →

   800-1100°C}

   Zn(v) + CO + CO₂

   Zn(v)

   {

   →

   ≤900°C}

   Zn(l)

8. Gather the zinc from the lower (cooler) container

Electrolysis

zinc sulfate

Zinc sulfate can be electrolytically separated in sulfuric acid, producing oxygen and excess sulfuric acid as a side stream. The reaction is fairly straightforward:

2 ZnSO₄ + 2 H₂O

{H₂SO₄

→

4.5v}

2 Zn + 2 H₂SO₄ + O₂

Wikipedia offers some numbers on efficiency

There are two common processes for electrowinning the metal. The former uses a 10% sulfuric acid solution as the electrolyte, with current density of 270–325 amperes per square meter. The latter uses 22–28% sulfuric acid solution as the electrolyte with a current density of about 1,000 amperes per square metre. The latter gives better purity and has higher production capacity per volume of electrolyte, but has the disadvantage of running hotter and being more corrosive to the vessel in which it is done. In either of the electrolytic processes, each metric ton of zinc production expends about 3.9 MW·h (14 GJ) of electric power.

zinc chloride

Zinc chloride can also be electrolyzed completely into zinc and chlorine

ZnCl₂ → Zn + Cl₂