Alloy

Alloy:-

A mixture containing two or more metallic elements or metallic and nonmetallic elements usually fused together or dissolving into each other when molten; "brass is an alloy of zinc and copper .An alloy is actually a homogeneous mixture or metallic solid solution composed of two or more elements Complete solid solution alloys give single solid phase micro-structure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal (heat treatment) history. Alloys usually have different properties from those of the component elements

Alloying:-

Alloying a metal is done by combining it with one or more other metals or non-metals that often enhance its properties. For example, steel is stronger than iron, its primary element. The physical properties, such as density, reactivity, Young's modulus, and electrical and thermal conductivity, of an alloy may not differ greatly from those of its elements, but engineering properties such as tensile strength and shear strength may be substantially different from those of the constituent materials.

Ore:

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element(s).

The grade or concentration of an ore mineral, or metal, as well as its form of occurrence, will directly affect the costs associated with mining the ore. The cost of extraction must thus be weighted against the contained metal value of the rock to determine what ore can be processed and what ore is of too low a grade to be worth mining. Metal ores are generally oxides, sulfides,silicates, or "native" metals (such as native copper) that are not commonly concentrated in the Earth's crust or "noble" metals (not usually forming compounds) such as gold. The ores must be processed to extract the metals of interest from the waste rock and from the ore minerals. Ore bodies are formed by a variety of geological processes. The process of ore formation is called ore genesis.

Difference between alloy and ore:-

An alloy is a homogeneous mixture of elements; at least one of the elements must be a metal. An ore is a naturally occuring mixture (usually heterogenous) that contains a particular metal (or a compound of that metal) in amounts that make extraction of the metal economically worthwhile.

 Starch

Starch is a polysaccharides which are carbohydrate polymers consisting of tens to hundreds to several thousand monosaccharide units. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides are synthesized by plants, animals, and humans to be stored for food, structural support, or metabolized for energy. Plants store glucose as the polysaccharide starch. The cereal grains (wheat, rice, corn, oats, barley) as well as tubers such as potatoes are rich in starch. Starch can be separated into two fractions--amylose and amylopectin. Natural starches are mixtures of amylose (10-20%) and amylopectin (80-90%). Amylose forms a colloidal dispersion in hot water whereas amylopectin is completely insoluble. The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage.  The graphic on the left shows a very small portion of an amylose chain. All of the monomer units are alpha -D-glucose, and all the alpha acetal links connect C # 1 of one glucose to C # 4 of the next glucose.

Iodometry:

Iodometry is one of the most important redox titration methods. Iodine reacts directly, fast and quantitively with many organic and inorganic substances. Thanks to its relatively low, pH independent redox potential, and reversibility of the iodine/iodide reaction, iodometry can be used both to determine amount of reducing agents (by direct titration with iodine) and of oxidizing agents (by titration of iodine with thiosulfate). In all cases the same simple and reliable method of end point detection, based on blue starch complex, can be used.

Reversible iodine/iodide reaction mentioned above is

2I^- ↔ I₂ + 2e^-

and obviously whether it should be treated as oxidation with iodine or reduction with iodides depends on the other redox system involved.

Second important reaction used excesivelly in iodometry is reduction of iodine with thiosulfate:

2S₂O₃^2- + I₂ → S₄O₆^2- + 2I^-

Use of chemicals:-

Thiosulfate:-

Thiosulfate anion characteristically reacts with dilute acids to produce sulfur, sulfur dioxide and water:^[1]

Na₂S₂O₃ + 2HCl → 2NaCl + S + SO₂ + H₂O

This reaction is known as a "clock reaction", because when the sulfur reaches a certain concentration the solution turns from colorless to a pale yellow. This reaction has been employed to generate colloidal sulfur. When the protonation is conducted at low temperatures, H₂S₂O₃ (thiosulfuric acid) can be obtained.

In analytical chemistry, the most important use comes from the fact that the thiosulfate anion reacts stoichiometrically with iodine, reducing it to iodide as it is oxidized to tetrathionate:

2 S₂O₃²⁻(aq) + I₂(aq) → S₄O₆²⁻(aq) + 2 I⁻(aq)