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Related Concept Videos

Expressing Solution Concentration02:48

Expressing Solution Concentration

A solute is a component of a solution that is typically present at a much lower concentration than the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
Concentrations may be quantitatively assessed using a wide variety of measurement units, each convenient for particular applications. Molarity (M) is a useful concentration unit for many applications in chemistry.
Calculating Equilibrium Concentrations02:05

Calculating Equilibrium Concentrations

Being able to calculate equilibrium concentrations is essential to many areas of science and technology—for example, in the formulation and dosing of pharmaceutical products. After a drug is ingested or injected, it is typically involved in several chemical equilibria that affect its ultimate concentration in the body system of interest. Knowledge of the quantitative aspects of these equilibria is required to compute a dosage amount that will solicit the desired therapeutic effect.
A more...
Solution Concentration and Dilution02:59

Solution Concentration and Dilution

The relative amount of a given solution component is known as its concentration. Often, though not always, a solution contains one component with a concentration that is significantly greater than that of all other components. This component is called the solvent and may be viewed as the medium in which the other components are dispersed or dissolved. Solutions in which water is the solvent are, of course, very common on our planet. A solution in which water is the solvent is called an aqueous...
Le Chatelier's Principle: Changing Concentration02:27

Le Chatelier's Principle: Changing Concentration

A system at equilibrium is in a state of dynamic balance, with forward and reverse reactions taking place at equal rates. If an equilibrium system is subjected to a change in conditions that affects these reaction rates differently (a stress), then the rates are no longer equal and the system is not at equilibrium. The system will subsequently experience a net reaction in the direction of a greater rate (a shift) that will re-establish the equilibrium. This phenomenon is summarized by Le...
Calculating the Equilibrium Constant02:46

Calculating the Equilibrium Constant

The equilibrium constant for a reaction is calculated from the equilibrium concentrations (or pressures) of its reactants and products. If these concentrations are known, the calculation simply involves their substitution into the Kc expression.
For example, gaseous nitrogen dioxide forms dinitrogen tetroxide according to this equation:
The Small x Assumption02:20

The Small x Assumption

If a reaction has a small equilibrium constant, the equilibrium position favors the reactants. In such reactions, a negligible change in concentration may occur if the initial concentrations of reactants are high and the Kc value is small. In such circumstances, the equilibrium concentration is approximately equal to its initial concentration. This estimation can be used to simplify the equilibrium calculations by assuming that some equilibrium concentrations are equal to the initial...

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Optimization of Processing Technology for Tiebangchui with Zanba Based on CRITIC Combined with Box-Behnken Response Surface Method
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Correcting the concentration index: a comment.

Adam Wagstaff1

  • 1The World Bank, 1818 H Street NW, Washington, DC 20433, USA. awagstaff@worldbank.org

Journal of Health Economics
|January 27, 2009
PubMed
Summary

The concentration index (CI) measures income-related health inequality. This paper critiques a proposed correction, arguing it inappropriately shifts focus from relative to absolute inequality for interval-scale variables.

Area of Science:

  • Health Economics
  • Econometrics

Background:

  • The concentration index (CI) is a key measure for assessing income-related health inequality.
  • Erreygers proposed a new CI measure to address limitations with binary health indicators and interval-scale variables.

Discussion:

  • This commentary questions the suitability of adapting the CI for interval-scale variables, arguing it fundamentally alters the measure towards absolute inequality.
  • The author defends their original normalization approach, clarifying its intent was not to produce an absolute inequality measure.
  • It is demonstrated that both the original and Erreygers's indices may not be pure relative inequality measures due to addressing bounds issues.

Key Insights:

  • Adapting the CI for interval-scale variables may be conceptually flawed, shifting focus from relative to absolute inequality.

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  • The normalization of the CI has specific intentions regarding relative inequality measurement.
  • Addressing the bounds problem in inequality indices can lead to deviations from pure relative inequality.

    • Outlook:

    • Further refinement of inequality measures is needed to accurately capture relative and absolute disparities in health.
    • Clarifying the theoretical underpinnings of inequality indices is crucial for appropriate application.
    • The debate highlights the complexities in measuring health inequality across different variable types.