Potassium

 

Potassium

Chemical formula	K
Atomic Number	19
OTP appearance	grey solid
Molar Mass(g/mol)	39.1
Density(g/cc)	0.8
Melting Point(°C)	63.5
Boiling Point(°C)	759
NFPA 704	3 3 2 W

Uses

Primary

• Important chemical substituent
• Important halide exchange metal

Natural occurrence

• Elemental potassium does not occur naturally.
• potassium chloride occurs naturally in salt water and the mineral sylvite
• potassium carbonate occurs naturally in wood wood ash

Hazards

• Potassium will spontaneously (exothermically) oxidize when exposed to air
• Potassium will react violently when exposed to water, producing heat and flammable hydrogen gas, a potentially bad combination.
• Potassium is very reactive in general

Production

File:KClNaClBps.png

Gaseous extraction of elemental potassium

• from -chloride and sodium metal by thermal reduction and halide exchange. KCl and an excess of Na are intermixed in an oxygen-free environment and the temperature is maintained above 801°C and below 1156°C, the potassium escapes as a gas, leaving a mixture of molten sodium and molten salt behind.

  KCl(l) + Na(l)

  {

  →

  1000°C}

  K(g) + NaCl(l)

• from -chloride via electrolysis. cf. Downs cell

  2 KCl(l)

  {

  →

  770°C, 7-10V}

  2 K(l) + Cl₂(g)

Purification

==Testing

See Also

• Downs cell
• Salt and sodium