52nd International Chemistry Olympiad, Istanbul, TURKEY
Preparatory problems: THEORETICAL
Problem 12. Blue to Green, Turquoise The beauty of the turquoise color of Lake Salda, where blue meets white sands, fascinates those who see it. Lake Salda, in the southern province of Burdur’s Yeşilova district, has been referred to as “Turkey’s Maldives” in recent years for its white sandy beaches and turquoise water. In fact, turquoise is an opaque, blue to green mineral that is a hydrated phosphate of copper and aluminum with the chemical formula of CuAl6(PO4)4(OH)8·4H2O, and is known as a gemstone. The word turquoise dates back to the 17th century and is derived from the French turquois, meaning "Turkish" because the mineral was first brought to Europe through Turkey, from mines in the historical Khorasan Province of Persia. Phosphorus, which is also in the structure of turquoise, is an essential part of life. Without the phosphates in biological molecules such as ATP, ADP, and DNA, we would not survive. Phosphorus compounds can be found in the minerals in our bones and teeth. With few exceptions, minerals containing phosphorus are in the maximally oxidized state as inorganic phosphate rocks, which are partially made of apatite, and they are today the chief commercial source of this element. Phosphate products are used as fertilizers in agriculture. They are also used in animal feeds, as a leavening agent in baking powder and flour, as an additive to beverages, and in pharmaceuticals. Industrial uses include water softening, rust proofing, fire proofing, in insecticides and detergents, and for the manufacture of elemental phosphorus.
Lake Salda There are three important allotropes of phosphorus: X, Y, and Z. However, another form of phosphorus, W, also exists (given below). X is a soft, waxy solid. It is exceptionally harmful 79
