Question

In your own words, define the following terms: (a) polyhalide ion; (b) polyphosphate; (c) interhalogen; (d) disproportionation.

Short answer

Polyhalide ion: An ion that contains atoms of the same halogen element in different oxidation states; Polyphosphate: A compound derived from multiple phosphate units via dehydration synthesis; Interhalogen: A molecule formed from two different halogens; Disproportionation: A redox reaction where an element from a reactant is simultaneously oxidized and reduced, resulting in two different products.

Step-by-step solution

Define Polyhalide Ion

A polyhalide ion is a type of ion that contains atoms of the same halogen element in different oxidation states. Examples include iodine pentoxide (\(I_2O_5\)).

Define Polyphosphate

Polyphosphates are compounds derived from multiple phosphate units. These units are joined together by dehydration synthesis, resulting in phosphoric anhydride bonds. A common example is the adenosine triphosphate (ATP), which has three interconnected phosphate groups.

Define Interhalogen

Interhalogens are a group of molecules formed from two different halogens. They can be of several types: diatomic, triatomic, tetraatomic, and hexatomic. An example of an interhalogen compound is iodine monofluoride (\(IF\)).

Define Disproportionation

Disproportionation refers to a specific type of redox reaction in which an element from a reactant is simultaneously oxidized and reduced, resulting in two different products. A common example involves the conversion of hydrogen peroxide (\(H_2O_2\)) into water and oxygen.

Key concepts

Polyhalide Ion

Polyhalide ions are fascinating as they contain multiple halogen atoms, typically from the same element, in various oxidation states. These ions often involve a central halogen atom surrounded by others, forming a larger molecule. For example, in the case of iodine, a known polyhalide ion is the triiodide ion (\[ I_3^- \]), which is commonly encountered in starch-iodine chemistry for detecting starch presence. Triiodide ions are formed by the combination of iodine (\[ I_2 \]) and iodide (\[ I^- \]) ions.
This mixture results in different oxidation states for the iodine molecules. They are particularly interesting due to their unique geometric configurations and roles in various qualitative tests. Students might often encounter these ions in the context of understanding halogen chemistry and its applications in analytical tests.

Polyphosphate

Polyphosphates are important in both biological systems and industrial processes. These compounds consist of multiple phosphate groups linked by phosphoric anhydride bonds. A familiar example of a polyphosphate is adenosine triphosphate (ATP)
, which acts as an energy currency in biological systems by storing and providing energy for cellular functions. In industry, polyphosphates are used for water softening and as additives in detergents and food products. Polyphosphates are formed through dehydration synthesis, where water is removed to create longer phosphate chains.
This process is essential in both organic and inorganic chemistry, highlighting the versatility and importance of phosphates in varying contexts.

Interhalogen

Interhalogens are unique molecules composed of two different halogen elements. These compounds exist in several forms depending on the number of halogen atoms involved, such as diatomic (\[ XY \]), triatomic (\[ XY_2 \]), tetraatomic (\[ XY_3 \]), and hexatomic (\[ XY_5 \]).
Where "X" is a heavier halogen, and "Y" is typically a lighter halogen. These compounds, such as iodine monochloride (\[ ICl \]), often possess interesting properties thanks to the difference in electronegativity between the constituent halogens.
This causes the molecules to exhibit polar characteristics, making them reactive and useful as intermediate compounds in chemical reactions. Additionally, interhalogens can act as halogenating agents in synthetic chemistry, thus occupying a significant role in industrial applications and research.

Disproportionation Reactions

Disproportionation reactions are a specific type of redox (reduction-oxidation) reaction where a single element undergoes both oxidation and reduction, producing two different products. A classic example is the reaction of hydrogen peroxide (\[ H_2O_2 \]) converting into water (\[ H_2O \]) and oxygen (\[ O_2 \]).
This reaction illustrates how hydrogen peroxide simultaneously decomposes into compounds where oxygen transitions from a -1 oxidation state in \[ H_2O_2 \] to 0 in \[ O_2 \] (oxidation) and -2 in \[ H_2O \] (reduction). Such reactions are essential in understanding the behavior of a particular element within different chemical environments.
They are notable in chemistry because they challenge students to think about how an element can simultaneously serve as an oxidant and a reductant, providing valuable insights into redox chemistry and the concept of oxidation states.