Concentration

Overview

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

,

**concentration**is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration. The term concentration can be applied to any kind of chemical mixture, but most frequently it refers to solute

Solute

Solute may refer to:* Solute, UMIK or UBOOK desolving in a substance,forming INT/INTY* Solute , a group of Paleozoic echinoderms...

s in homogeneous solution

Solution

In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

s.

Often in informal, non-technical language, concentration is described in a qualitative way, through the use of adjectives such as "dilute" for solutions of relatively low concentration and "concentrated" for solutions of relatively high concentration.

Unanswered Questions

Encyclopedia

In chemistry

,

s in homogeneous solution

s.

(for example, alcohol), or reduce the amount of solvent

(for example, water). By contrast, to

. If additional solute is added to a saturated solution, it will not dissolve (except in certain circumstances, when supersaturation

may occur). Instead, phase separation will occur, leading to coexisting phases (either completely separated or mixed as a suspension

. The point of saturation depends on many variables such as ambient temperature and the precise chemical nature of the solvent and solute.

of a constituent divided by the volume of the mixture :

The SI-unit

is kg/m

of a constituent divided by the volume of the mixture :

The SI-unit

is mol/m

The SI-unit

is 1/m

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is m

of a constituent divided by the mass of the solvent (

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

for molality is mol/kg.

of a constituent divided by the total amount of all constituents in a mixture :

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is mol/mol. However, the deprecated parts-per notation

is often used to describe small mole fractions.

Amount of substance is a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units defines the amount of substance to be...

of a constituent divided by the total amount of all

If is much smaller than , the mole ratio is almost identical to the mole fraction.

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is mol/mol. However, the deprecated parts-per notation

is often used to describe small mole ratios.

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is kg/kg. However, the deprecated parts-per notation

is often used to describe small mass fractions.

If is much smaller than , the mass ratio is almost identical to the mass fraction.

The SI-unitThe International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is kg/kg. However, the deprecated parts-per notationIn science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

is often used to describe small mass ratios.

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

,

**concentration**is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration. The term concentration can be applied to any kind of chemical mixture, but most frequently it refers to soluteSolute

Solute may refer to:* Solute, UMIK or UBOOK desolving in a substance,forming INT/INTY* Solute , a group of Paleozoic echinoderms...

s in homogeneous solution

Solution

In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

s.

## Qualitative description

Often in informal, non-technical language, concentration is described in a qualitative way, through the use of adjectives such as "dilute" for solutions of relatively low concentration and "concentrated" for solutions of relatively high concentration. To**concentrate**a solution, one must add more soluteSolution

In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

(for example, alcohol), or reduce the amount of solvent

Solvent

A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

(for example, water). By contrast, to

**dilute**a solution, one must add more solvent, or reduce the amount of solute. Unless two substances are*fully*miscible there exists a concentration at which no further solute will dissolve in a solution. At this point, the solution is said to be saturatedSaturation (chemistry)

In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...

. If additional solute is added to a saturated solution, it will not dissolve (except in certain circumstances, when supersaturation

Supersaturation

The term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances...

may occur). Instead, phase separation will occur, leading to coexisting phases (either completely separated or mixed as a suspension

Suspension (chemistry)

In chemistry, a suspension is a heterogeneous fluid containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than 1 micrometer. The internal phase is dispersed throughout the external phase through mechanical agitation, with the use of certain...

. The point of saturation depends on many variables such as ambient temperature and the precise chemical nature of the solvent and solute.

### Mass concentration

The mass concentration is defined as the massMass

Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

of a constituent divided by the volume of the mixture :

The SI-unit

International System of Units

The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is kg/m

^{3}.### Molar concentration

The molar concentration is defined as the amountAmount of substance

Amount of substance is a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units defines the amount of substance to be...

of a constituent divided by the volume of the mixture :

The SI-unit

International System of Units

The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is mol/m

^{3}. However, more commonly the unit mol/L is used.### Number concentration

The number concentration is defined as the number of entities of a constituent in a mixture divided by the volume of the mixture :The SI-unit

International System of Units

The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...

is 1/m

^{3}.### Volume concentration

The**volume concentration**(also called**volume fraction**) is defined as the volume of a constituent divided by the volume of all consituents of the mixture prior to mixing:The SI-unit

International System of Units

is m

^{3}/m^{3}.## Related Quantities

Several other quantities can be used to describe the composition of a mixture. Note that these should**not**be called concentrations.### Normality

Normality is defined as the molar concentration divided by an equivalence factor . Since the definition of the equivalence factor may not be unequivocal, IUPAC and NIST discourage the use of normality.### Molality

The molality of a solution is defined as the amountAmount of substance

Amount of substance is a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units defines the amount of substance to be...

of a constituent divided by the mass of the solvent (

**not**the mass of the solution):The SI-unit

International System of Units

for molality is mol/kg.

### Mole fraction

The mole fraction is defined as the amountAmount of substance

Amount of substance is a standards-defined quantity that measures the size of an ensemble of elementary entities, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units defines the amount of substance to be...

of a constituent divided by the total amount of all constituents in a mixture :

The SI-unit

International System of Units

is mol/mol. However, the deprecated parts-per notation

Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

is often used to describe small mole fractions.

### Mole ratio

The mole ratio is defined as the amountAmount of substance

of a constituent divided by the total amount of all

*other*constituents in a mixture:If is much smaller than , the mole ratio is almost identical to the mole fraction.

The SI-unit

International System of Units

is mol/mol. However, the deprecated parts-per notation

Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

is often used to describe small mole ratios.

### Mass fraction

The mass fraction is the fraction of one substance with mass to the mass of the total mixture , defined as:The SI-unit

International System of Units

is kg/kg. However, the deprecated parts-per notation

Parts-per notation

In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement...

is often used to describe small mass fractions.

### Mass ratio

The mass ratio is defined as the mass of a constituent divided by the total mass of all*other*constituents in a mixture:If is much smaller than , the mass ratio is almost identical to the mass fraction.

The SI-unit

International System of Units

is kg/kg. However, the deprecated parts-per notation

Parts-per notation

is often used to describe small mass ratios.

## Dependence on volume

Concentration depends on the variation of the volume of the solution due mainly to thermal expansion.## Table of concentrations and related quantities

Concentration type | Symbol | Definition | SI-unit | other unit(s) |
---|---|---|---|---|

mass concentration | or | kg/m^{3} |
g/100mL (=g/dL) | |

molar concentration | mol/m^{3} |
M (=mol/L) | ||

number concentration | 1/m^{3} |
1/cm^{3} |
||

volume concentration | m^{3}/m^{3} |
|||

Related quantities | Symbol | Definition | SI-unit | other unit(s) |

normality | mol/m^{3} |
M (=mol/L) | ||

molality | mol/kg | |||

mole fraction | mol/mol | ppm, ppb, ppt | ||

mole ratio | mol/mol | ppm, ppb, ppt | ||

mass fraction | kg/kg | ppm, ppb, ppt | ||

mass ratio | kg/kg | ppm, ppb, ppt |

## See also

- Serial dilutionSerial dilutionA serial dilution is the stepwise dilution of a substance in solution. Usually the dilution factor at each step is constant, resulting in a geometric progression of the concentration in a logarithmic fashion. A ten-fold serial dilution could be 1 M, 0.1 M, 0.01 M, 0.001 M.....
- Practical examples of 1 and 2 normal acids in biochemistry