Skip to main content
Select Source:

concentration

concentration, in chemistry, measure of the relative proportions of two or more quantities in a mixture. The concentration of a solute is very important in studying chemical reactions because it determines how often molecules collide in solution and thus indirectly determines the rates of reactions and the conditions at equilibrium (see chemical equilibrium).

Concentration may be expressed in a number of ways. The simplest statement of the concentrations of the components of a mixture is in terms of their percentages by weight or volume. Mixtures of solids or liquids are frequently specified by weight percentage concentrations, such as alloys of metals or mixtures used in cooking, whereas mixtures of gases are usually specified by volume percentages. Very low concentrations may be expressed in parts per million (ppm), as in specifying the relative presence of various substances in the atmosphere.

In addition to these means of expressing concentration, several others are defined especially for describing solutions: molarity, molality, mole fraction, formality, and normality. Some of these define the concentration of the solute in reference to the amount of solvent, others in reference to the total amount of solution. The molarity of a solution is the number of moles of solute per liter of solution; e.g., a solution of glucose in water containing 180.16 grams (1 gram-molecular weight, or mole) of glucose per liter of solution is referred to as one molar (1 M). The molality of a solution is the number of moles of solute per 1,000 grams of solvent; a solution prepared by dissolving 180.16 grams of glucose in 1,000 grams of water is one molal (1 m). The mole fraction of a solution is the ratio of moles of solute to the total number of moles in the solution. Since ionic compounds, such as sodium chloride, NaCl, do not occur as molecules, their concentrations cannot be expressed in terms of molarity, molality, or mole fraction. Instead, the concentration of an ionic compound in solution may be given by its formality, the number of gram-formula weights of the compound per liter of solution; e.g., a solution containing 58.44 grams (one gram-formula weight) of NaCl per liter of solution is one formal (1 F). In considering the reactions of certain solutions in combination, for example the neutralization of acids and bases, a useful expression of the concentration is the normality of each solution, the number of gram-equivalent weights of solute per liter of solution (see equivalent weight); e.g., a solution containing 49.04 grams (one gram-equivalent weight) of sulfuric acid, H2SO4, per liter of solution is one normal (1 N). Concentrations of solutions may also frequently be given in terms of the weight of solute in a given volume of solvent or solution.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"concentration." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"concentration." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/concentration

"concentration." The Columbia Encyclopedia, 6th ed.. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/concentration

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

concentration

con·cen·tra·tion / ˌkänsənˈtrāshən/ • n. 1. the action or power of focusing one's attention or mental effort. ∎  (concentration on/upon) dealing with one particular thing above all others: concentration on the needs of the young can mean that the elderly are forgotten. 2. a close gathering of people or things: the largest concentration of Canada geese on earth. ∎  the action of gathering together closely: the concentration of power . 3. the relative amount of a given substance contained within a solution or in a particular volume of space; the amount of solute per unit volume of solution: the gas can collect in dangerous concentrations. ∎  the action of strengthening a solution by the removal of water or other diluting agent or by the selective accumulation of atoms or molecules.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"concentration." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"concentration." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/concentration

"concentration." The Oxford Pocket Dictionary of Current English. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/concentration

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

concentration

concentration The quantity of dissolved substance per unit quantity of solvent in a solution. Concentration is measured in various ways. The amount of substance dissolved per unit volume (symbol c) has units of mol dm–3 or mol l–1. It is now called `concentration' (formerly molarity). The mass concentration (symbol ρ) is the mass of solute per unit volume of solvent. It has units of kg dm–3, g cm–3, etc. The molal concentration (or molality; symbol m) is the amount of substance per unit mass of solvent, commonly given in units of mol kg–1.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"concentration." A Dictionary of Biology. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"concentration." A Dictionary of Biology. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/concentration-0

"concentration." A Dictionary of Biology. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/concentration-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

concentration

concentration
1. In chemistry, the number of molecules or ions in a given volume of a substance, expressed as moles of solute per litre of solution (molarity).

2. In mineral processing, the production of a concentrate from its ore, or the process of increasing concentration by evaporation, etc.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"concentration." A Dictionary of Earth Sciences. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"concentration." A Dictionary of Earth Sciences. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/concentration

"concentration." A Dictionary of Earth Sciences. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/concentration

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Concentration

Concentration

a concentrated collection or mass; a distillate.

Examples: concentration of broken beams, 1634; of lunar beams, 1691; of related species, 1881; of hostile tribes, 1841; of forces, 1804.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Concentration." Dictionary of Collective Nouns and Group Terms. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"Concentration." Dictionary of Collective Nouns and Group Terms. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/concentration

"Concentration." Dictionary of Collective Nouns and Group Terms. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/education/dictionaries-thesauruses-pictures-and-press-releases/concentration

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Concentration

Concentration

Concentration is the degree to which one substance is present in a mixture. The concentration of each substance in a mixture can be expressed in mass or volume units. The components of the mixture can be gases, liquids, or solids.

Earths atmosphere, for example, is a mixture of gases, and 78% of the total volume is nitrogen gas. (Percentages are the number of parts of a certain substance per hundred parts of the mixture.) In other words, the concentration of nitrogen in Earths atmosphere is 78%. Different types of steel are mixtures of iron with other elements. For example, stainless steel has close to 20%, by weight, of chromium. Sometimes a combination of mass and volume measurements are used; vinegar can be said to be a 5% solution of acetic acid, meaning 5 g of acetic acid per 100 mL of solution. Because it is not usually practical to analyze the whole body of substance in question (Earths atmosphere, for example), only samples are taken. Getting a true representation of the whole is crucial, or the concentration determined will not be accurate. For example, the concentration of nitrogen in the atmosphere changes slightly with altitude; sampling only at sea level would not be sufficient to characterize the whole atmosphere.

Many commonly used mixtures are liquid solutions. For chemical reactions, molarity is a useful unit of concentration. It is the number of moles of solute per liter of solution. Concentrated hydrochloric acid is 12 M, meaning that there are 12 moles of hydrogen chloride per liter of water solution. Other useful units of concentrations are molality, or the number of moles of solute per kilogram of solvent; mole fraction, which is the ratio of the numbers of moles of solute and solution; and normality, which is the number of chemical equivalents per liter of solution.

When very small amounts of a substance are present, parts per million or parts per billion may be used. A sample of tap water may contain 35 parts per million of dissolved solids. The concentration of a radioactive gas such as radon in air can be reported in picocuries per liter, or the amount of radioactivity per unit volume of air. For homes that are tested for the presence of radon, the safe limit is about 4 picocuries per liter. Exposure levels of dust or vapors in air may be given in units of mass of substance per volume of air. The maximum acceptable level for human exposure to ammonia vapor, for example, is 27 mg per cubic meter of air for short term exposure, that is, during a 15-minute period. Because modern analytical instruments require only small samples, results are often reported in milligrams per milliliter or nano-grams per milliliter. Clinical laboratory reports of substances in blood or urine may be reported as milligrams per deciliter.

Concentration, as a verb, refers to the process of removing solvent from a solution to increase the proportion of solute. Concentration of a salt solution is achieved, for example, by allowing water to evaporate from the solution.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Concentration." The Gale Encyclopedia of Science. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"Concentration." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/concentration

"Concentration." The Gale Encyclopedia of Science. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/concentration

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Concentration

Concentration

Concentration is a ratio of how much of one ingredient is present in a mixture, compared to the whole mixture or compared to the main ingredient, often the solvent. The amounts of each substance can be expressed in mass or volume units, and many different units can be used. The components of the mixture can be gases, liquids, or solids.

Earth's atmosphere, for example, is a mixture of gases, and 78% of the total volume is nitrogen gas. (Percentages are the number of parts of a certain substance per hundred parts of the mixture.) Different types of steel are mixtures of iron with other elements. For example, stainless steel has close to 20%, by weight, of chromium. Sometimes a combination of mass and volume measurements are used; vinegar can be said to be a 5% solution of acetic acid , meaning 5 g of aceticacid per 100 mL of solution. Because it is not usually practical to analyze the whole substance in question, (Earth's atmosphere, for example) only samples are taken. Getting a true representation of the whole is crucial, or the concentration determined will not be accurate. For example, the concentration of nitrogen in the atmosphere changes slightly with altitude.

Many commonly used mixtures are liquid solutions. For chemical reactions , molarity is a useful unit of concentration. It is the number of moles of solute per liter of solution. Concentrated hydrochloric acid is 12 M, meaning that there are 12 moles of hydrogen chloride per liter of water solution. Other useful units of concentrations are molality, or the number of moles of solute per kilogram of solvent; mole fraction, which is the ratio of the numbers of moles of solute and solution; and normality, which is the number of chemical equivalents per liter of solution.

When very small amounts of a substance are present, parts per million or parts per billion may be used. A sample of tap water may contain 35 parts per million of dissolved solids. The concentration of a radioactive gas such as radon in air can be reported in picocuries per liter, or the amount of radioactivity per unit volume of air. For homes that are tested for the presence of radon, the safe limit is about 4 picocuries per liter. Exposure levels of dust or vapors in air may be given in units of mass of substance per volume of air. The maximum acceptable level for human exposure to ammonia vapor, for example, is 27 mg per cubic meter of air for short term exposure, that is, during a 15-minute period. Because modern analytical instruments require only small samples, results are often reported in milligrams per milliliter or nanograms per milliliter. Clinical laboratory reports of substances in blood or urine may be reported as milligrams per deciliter.

Concentration also refers to the process of removing solvent from a solution to increase the proportion of solute. The Dead Sea becomes more concentrated in salts as water evaporates from the surface. Ores are produced by the concentration of valuable minerals , such as those containing gold or silver, in small region of Earth's crust.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Concentration." The Gale Encyclopedia of Science. . Encyclopedia.com. 17 Nov. 2018 <https://www.encyclopedia.com>.

"Concentration." The Gale Encyclopedia of Science. . Encyclopedia.com. (November 17, 2018). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/concentration-0

"Concentration." The Gale Encyclopedia of Science. . Retrieved November 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/concentration-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.