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The plimsoll symbol as used in shipping
The plimsoll symbol as used in shipping

In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). Waterline refers to an imaginary line marking the level at which Ship or Boat floats in the Water. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. This pressure was changed from 1 atm (101. The Standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of Pressure (symbol atm 325 kilopascals) by IUPAC in 1990. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization [1] The standard state of a material can be defined at any given temperature, most commonly 25 degrees Celsius, although quite a few texts (especially in related disciplines such as physics and engineering) use 0 degrees Celsius for Standard Temperature and Pressure (STP). The Celsius Temperature scale was previously known as the centigrade scale. The Celsius Temperature scale was previously known as the centigrade scale. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made

It should be noted that the standard state is an arbitrarily chosen non-zero value, not a natural zero point. For the concept of arbitrariness in trademark law see Trademark distinctiveness.

For a given material or substance, the standard state is the reference state for the material's thermodynamic state properties such as enthalpy, entropy, Gibbs free energy, and for many other material standards. A chemical substance is a Material with a definite chemical composition. In Thermodynamics and molecular chemistry, the enthalpy (denoted as H, h, or rarely as χ) is a quotient or description of In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy In Thermodynamics, the Gibbs free energy ( IUPAC recommended name Gibbs energy or Gibbs function) is a Thermodynamic potential which The standard enthalpy of formation for an element in its standard state is 0. The standard enthalpy of formation or "standard heat of formation" of a compound is the change of Enthalpy that accompanies the formation of 1 mole of a

When the standard state is referred to a solute in a solution, or to a chemical reaction, it also includes the condition that the concentrations of all solutes are at unity (or another designated quantity) for whatever measure of concentration is specified. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances If that is molarity that would be 1 mol·dm-3 and for molality 1 mol·kg-1 assuming the solution infinite-dilution behaviour. In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this A decimetre ( American spelling: decimeter, symbol dm) is a unit of Length in the Metric system, equal to one tenth In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance If mole fraction is used, the pure liquid or solid is the standard state (x=1). In Chemistry, the mole fraction of a component in a Mixture is the relative proportion of molecules belonging to the component to those in the mixture As it is possible (and in principle legitimate) to take a different unit for each of the species in the reaction, the nature of the standard state needs to be specified when reporting or tabulating. Although a definition involving 1 mol/L (molarity at unity) of A in combination with pure B (mole fraction at unity) is clearly a condition that can never be met, such a non-existent standard state nevertheless leads to a consistent system of tabulated values, provided it is used consistently by all. Of course these values are different from those where a different standard state is adopted.

Contents

Symbol

In the time of their development (the 19th century) the Plimsoll - symbol was adopted as a superscript o to indicate the non-zero nature of the chosen reference state. For typographic reasons this symbol is often abridged to a rather misleading zero superscript 0 in later texts.

At elevated temperature and pressure

In chemistry of solutions at elevated temperatures and pressures, the term "standard state" often denotes the hypothetical standard concentration, typically:

It does not imply any particular temperature or total system pressure because, although contrary to IUPAC recommendation, it is more convenient when describing solutions over a wide temperature and pressure ranges. [2]

See also

Notes

  1. ^ International Union of Pure and Applied Chemistry. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization "standard conditions for gases". Compendium of Chemical Terminology Internet edition. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry.
  2. ^ V. Majer, J. Sedelbauer and Wood, "Calculations of standard thermodynamic properties of aqueous electrolytes and nonelectrolytes. " Chapter 4 in: "Aqueous Systems at Elevated Temperatures and Pressures. Physical Chemistry of Water, Steam and Hydrothermal Solutions", D. A. Palmer, R. Fernandez-Prini, and A. Harvey (editors), Elsevier, 2004.

External links

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