1. Alkali metals provide links to the Periodic Table and periodic properties
2. Extraction from naturally occurring ores and chemical reactivity of alkali metal elements are both examples of oxidation-reduction reactions.
3. Sodium is obtained by the electrolysis of a mixture of 60% by mass of calcium chloride, and 40% by mass of sodium chloride. The mixture melts at 580 °C, whereas pure sodium chloride melts at 801 °C. This is an example of how the concept of freezing point depression can have practical applicationsÑin this case, a marked reduction in the fuel costs needed to melt the electrolyte. (Both the sodium and calcium are liberated at a stainless steel cathode in the Downs cell and rise through a cooled collecting pipe. The calciumÑmelting point, 851 °CÑsolidifies and falls back into the melt while the sodiumÑ melting point, 98°CÑrises and condenses in the collecting chamber.) Another example of the use of freezing point depression involves the preparation of lithium. Lithium is prepared from spodumene, LiAl(SiO3)2:
KCl lowers the melting point of LiCl from 614 °C to 450 °C.
Between Chemistry and Other Disciplines
Physics
The bright yellow light of the sodium spectrum is one of the dominant colors in the sun's spectrum (and many street lamps).
Earth Science
1. Deposits of sodium and potassium compounds (e.g., NaCl, KNO3) are found throughout the world. Large salt deposits are found in Oklahoma, Texas and Kansas.
2. Rivers dissolve and carry 160 million tons of salt to the oceans each year.
3. The sodium chloride from all the oceans would occupy 1.9 x 107 km3 . This volume is equivalent to 150% of the North American continent above sea level. This quantity of solid would form a column with an area of 1 km 2 and a height 47 times the distance to the moon.
4. The Cheshire salt field in Great Britain is 60 km x 24 km with a thickness of 400 m and contains 1 x 1014 kg (1 x 1011 metric tons) of sodium chloride, NaCl.
5. Analysis of mineral water from locations such as Durkheim, Ungemach, and Bourbonne-les-Bains shows Rb+ and Cs+ at levels as high as 18.7 mg/L for Rb+ and 32.5 mg/L for Cs+.
Biology
1. The analysis of blood serum of all animals indicates 0.022% potassium and 0.32% sodium by mass. The milk of meat eating animals contains equal amounts of the two elements (a 1:1 ratio), whereas in the milk of herbivores and humans, the K to Na ratio is 3.5:1.
2. KI is added to table salt (NaCl) sold in supermarkets to help prevent goiter, a disease associated with iodine deficiency.
3. Marine plants take up potassium ion from the low concentrations in sea water. Potassium salts can be extracted from the ashes of calcined kelp.
4. The perspiration of sheep is so rich in potassium salts that the brown solution obtained from washing the wool in water yields, after evaporation and heating the residue, 5 parts of K2CO3 for every 100 parts of wool.
5. The minimum amount of potassium in a fertile soil is 0.01% by mass. An acre of trees removes about 1.5 lbs of K2CO3 from the soil each year. Since other growing plants remove even greater amounts, the potassium must be replenished through the addition of fertilizers.
6. Rubidium salts are absorbed from the soil by plants, but cesium salts are vegetable poisons.
Personal
1. Synthetic greases (one component is lithium stearate) are produced using tallow (animal fat), lithium hydroxide, and water, analogous to the production of soaps using potash (KOH).
2. Baking soda, NaHCO3, relieves stomach acidity by the reaction:
3. Potash (KOH) is used to make soap, along with animal fat or tallow.
4. The basic mixture used in fireworks is called black powderÑa mixture of powdered potassium nitrate (KNO3) carbon, and sulfur. In place of potassium nitrate, potassium chlorate (KClO3) or potassium perchlorate (KClO4) is often used. To produce the special effects so necessary to pyrotechnic displays, the following compounds are used.
5. For many years (approximately 1930-1980) the primary industrial use for sodium was in the manufacture of tetraethyl lead, Pb(C2H5)4, which was used in most motor fuels to improve octane number and reduce valve knock. Tetraethyl lead does not contain sodium, but the sodium was used to make Na4Pb, which was reacted with ethyl chloride to make tetraethyl lead.
6. Some common names of alkali metal compounds:
Community
1. KO2, potassium superoxide, is used in self-contained breathing apparatus for firefighters. Moisture in breath reacts to make oxygen.
A subsequent reaction removes exhaled carbon dioxide.
2. Sodium vapor lamps are used to illuminate roadways.
3. Oxides of calcium are used to neutralize acids in lakes affected by acid rain.
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