Chlorine

 

Chlorine

Chemical formula	{{#Chem:Cl}}
Atomic Number	17
OTP appearance	yellowish gas
Molar Mass(g/mol)	35.45
Density(g/cc)	0.0032
Melting Point(°C)	-101.5
Boiling Point(°C)	-34.04
Solubility in water(g/L)	4-10
Immediate Danger to Life and Health	10ppm (inh)
NFPA 704	0 4 0 OX

Chlorine is the only element that is also an industrial chemical.

Uses

Primary

• A key halogen material in general chemistry
• Produces bromine and iodine from saturated salt water

Secondary

• Combined with sodium hydroxide it produces bleach, salt, and water. By itself this process is inefficient, but is promoted by electrolysis.

Natural Sources

• Elemental chlorine does not occur naturally
• Chlorine is sourced from three naturally occurring chloride minerals:
  1. halite (sodium chloride, salt) in salt water and its evaporite deposits
  2. sylvite (potassium chloride)
  3. sal ammoniac (ammonium chloride) in volcanic, fumarole, and coal-fire areas.

Hazards

Chlorine (like fluorine and bromine) is very toxic

Production

Synthesis

• Thermal decomposition of copper (II) chloride produces chlorine gas:

  {{#Chem: 2CuCl2 { = 993°C} 2CuCl + Cl2(g) }}

• Heat hydrochloric acid and manganese dioxide. This is Scheel's original method.

  {{#Chem: 4HCl + MnO2 { = heat } MnCl2 + 2 H2O + Cl2}}

• Combine hydrochloric acid and an alkali hypochlorite

  {{#Chem: Ca(OCl)2 + 4HCl = CaCl2 + 2Cl2 + 2H2O}}

• Combine hydrochloric acid and potassium permanganate, producing potassium chloride, manganese chloride, water, and chlorine gas.

  {{#Chem: 16 HCl + 2 KMnO4 = 2 KCl + 2 MnCl2 + 8 H2O + 5 Cl2}}

Testing

test strip

1. Mix 20ubm water, 0.1ubm starch and 0.5ubm potassium iodide
2. soak paper in this solution, wring out/press
3. Expose the strip to the chlorine gas
4. Strip color change: goes from light beige/tan (starch) to inky (blur/violet/black) on exposure to chlorine gas.

Storage

• Toxic!
• Store in airtight, watertight glass / PTFE vessel

Disposal

• Bubble through double molar solution of sodium, potassium or calcium hydroxide, producing the salt and the hypochlorite. This is exothermic!

  {{#Chem: Cl2 + 2 NaOH(aq) = NaCl(aq) + NaOCl(aq) + H2O + heat}}