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Molbiotools is a collection of free online apps:

DNA Sequence Tools
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Lab Calculators
Math Calculators

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Chemical Calculator

Enter molar mass: g/mol

(equivalent to molecular weight - M. W. or formula weight - F. W.)

In the following boxes, always fill all but one field and click 'Calculate'. Don't use commas to separate thousands.

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Calculate

Molarity, Mass and Volume

Concentration (molarity):

Mass:

Volume:

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Calculate

Percentage and Molarity

Percent concentration (percentage): %

Molar concentration (molarity):

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Dilution of a Stock Solution

Stock solution concentration:

Final volume:

Final concentration:

Volume of stock solution:

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Dilution to a Desired Concentration

Initial concentration:

Initial volume:

Final concentration:

Volume of solvent to add:

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Calculate

Absorbance of a Solution

Absorbance:

Optical path: cm

Molar extinction coefficient: Lmol-1cm-1

Concentration:

Definitions and Formulas

Definitions of Basic Terms

Mole

The mole is the unit of measurement for amount of substance. It is defined as exactly 6.02214076×1023 (the Avogadro constant) particles, which may be atoms, molecules, ions, or electrons. The unit symbol is "mol".

Molar Mass

Molar mass is the mass of 1 mole of a substance, given in g/mol. The value of molar mass of a particular substance is near identical to its molecular weight (MW or M.W., sometimes also called formula weight - FW or F.W.), albeit the latter is used either without any unit or with a unit called the Dalton (Da).

Solute

A solute is a substance dissolved in another substance, known as a solvent.

Solvent

A solvent is a substance that dissolves a solute, resulting in a solution.

Solution

A solution, in chemistry, is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent.

Concentration

Concentration of a solution is the amount of solute dissolved in a volume unit of the solution. This amount can be expressed as moles, mass units, or percents.

Molar Concentration (molarity)

Molar concentration (also called molarity) is the number of molecules of a substance, expressed in mole units (see above), present in a certain volume of a solution. The most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L or mol⋅dm−3. The value of molarity is also often expressed as "x-molar", e.g. 2.5 M (read as "2.5-molar") where "M" stands for mol/L.

Molality

Molality is a measure of number of moles of solute present in 1 kg of solvent. This contrasts with the definition of molarity which is based on a specified volume of the solution.

Mass Concentration

Mass concentration is the ratio of the mass of a solute to the volume of the solution, usually expressed in grams per liter (g/L).

Percent Concentration

The percent concentration of a solution can be expressed as mass per mass (m/m or w/w), mass per volume (w/v), or volume per volume (v/v) percentage. Percent by mass (or weight), m/m or w/w is the mass of solute divided by the total mass of the solution, multiplied by 100 %. Percent by weight per volume (w/v), is the number of grams of solute in 100 mL of solution. Percent by volume (v/v) is the volume of solute divided by the total volume of the solution, multiplied by 100 %.

Stock Solution

A stock solution is a concentrated solution that will be diluted to some lower concentration, which is often referred to as a working or final concentration, for actual use. Stock solutions are used to save preparation time, reduce storage space, and improve the accuracy with which working lower concentration solutions are prepared.

Absorbance

Absorbance is a number that measures the attenuation of the transmitted light power in a solution. It is defined as the common logarithm of the ratio of incident to transmitted light power through a solution.

Molar Extinction Coefficient

The molar extinction coefficient or molar attenuation coefficient is a measurement of how strongly a chemical species attenuates light at a given wavelength. The SI unit of molar attenuation coefficient is the square metre per mole (m2/mol), but in practice, quantities are usually expressed in terms of M−1cm−1 or Lmol−1cm−1.

Calculations

The following symbols will be used in calculation formulas (units in square brackets):

n - number of moles [mol]
M - molar mass [g/mol]
c - molar concentration [mol/L]
m - mass [g]
V - volume [L]
Cw/v - percent concentration (w/v) [%]
Cv/v - percent concentration (v/v) [%]
ρ - mass density [kg/L]
A - absorbance
ε - molar extinction coefficient [Lmol−1cm−1]
l - optical path [cm]

You can use the molarity calculator located at the page top to calculate the mass, volume or concentration required to prepare a solution of compound of known molecular weight. For that, the following formulas will be used:

How to calculate the molarity of a solution?

Molarity of a solution is calculated directly from the defining formula; divide the mass of the substance by its molar mass and the solution volume:

c =
n
V
=
m
M × V

How to calculate the mass of a substance needed to prepare a solution of a certain molarity in a given volume?

Simply multiply the molarity, molar mass, and the solution volume values:

m = c × M × V

How to calculate the solution volume needed to obtain a desired molar concentration after dissolution of a certain mass of the substance?

Divide the mass value with the product of molar mass and molar concentration:

V =
m
M × c

You can use the second calculator (from page top) to convert between percent concentration and molar concentration. For that, the following formulas will be used:

How to convert percentage to molarity?

For w/v percentage, to find the molar concentration, multiply the percent concentration value by 10 to obtain the mass of the substance in 1 liter and then divide by the molar mass of the substance:

c =
10 × Cw/v
M

For v/v percentage, multiply 10 times the percent concentration value by the solution mass density to obtain the mass of the substance in 1 liter and then divide by the molar mass of the substance:

c =
10 × Cv/v × ρ
M

How to convert molarity to percentage concentration?

To get w/v percentage, multiply molarity by molar mass of the substance and divide by 10.

Cw/v =
c × M
10

To get v/v percentage, multiply molarity by molar mass of the substance and divide by 10 times the mass density of the solution.

Cv/v =
c × M
10 × ρ

You can use the third calculator (from page top) to calculate a dilution or preparation of a stock solution. For that, the following formulas will be used:

How to calculate the stock solution concentration needed to obtain the desired final (working) concentration after dilution of a specified volume of the stock solution into a given final volume?

Multiply the ratio of final and stock solution volumes by the required final concentration:

cstock = cfinal ×
Vfinal
Vstock

How to calculate the final concentration obtained by diluting a specified volume of the stock solution into a given final volume?

Multiply the ratio of stock and final solution volumes by the stock solution concentration:

cfinal = cstock ×
Vstock
Vfinal

How to calculate the volume of a stock solution needed to obtain the desired final (working) concentration after diluting the stock solution into a specified final volume?

Multiply the ratio of final and stock solution concentrations by final volume of the solution:

Vstock = Vfinal ×
cfinal
cstock

How to calculate the final volume of a solution required to obtain a desired final concentration after diluting a specified volume of the stock solution?

Multiply the ratio of stock and final solution concentrations by the stock solution volume:

Vfinal = Vstock ×
cstock
cfinal

You can use the fourth calculator (from page top) to calculate the dilution of entire solution required to adjust its concentration to a desired value. For that, the following formulas will be used:

How to calculate the volume to be added in order to reach a specified concentration after the dilution?

Multiply the initial volume by the ratio of initial and final concentrations diminished by 1:

Vadd = Vinitial × (
cinitial
cfinal
- 1 )

How to calculate the initial volume of a solution if you know the dilution factor and the volume to be added?

Dilution factor is the ratio of initial and final concentrations. Divide the volume to be added by the dilution factor value diminished by 1:

Vinitial = Vadd / (
cinitial
cfinal
- 1 )

How to calculate the final concentration of a solution obtained by adding a specified volume of solvent to a solution of known initial concentration and volume?

Divide the initial concentration value by the ratio of the volumes plus one:

cfinal = cinitial / (
Vadd
Vinitial
+ 1 )

How to calculate the initial concentration of a solution before it has been diluted by adding a specified volume of solvent to obtain a known final concentration?

Multiply the final concentration value by the ratio of added and initial volumes plus one:

cinitial = cfinal × (
Vadd
Vinitial
+ 1 )

You can use the fifth calculator (from page top) to calculate the absorbance of a solution of specified concentration or vice versa. For that, the following formulas will be used:

How to calculate the absorbance of a solution from its concentration?

Absorbance follows the Beer-Lambert law:

A = ε × l × c

How to calculate the concentration of a solution from its absorbance?

By rearranging the Beer-Lambert law we obtain the formula:

c =
A
ε × l

Tool Description

You can use Chemical Calculator to:

  • Calculate the mass or volume required to prepare a chemical solution that contains a specified molar concentration of a substance. Conversely, you can calculate the molarity of a solution prepared by dissolving a certain amount of a substance in a specified volume of a solvent.
  • Convert percent concentration (w/v or v/v) into molar concentration and vice versa.
  • Calculate the dilution of a stock solution to reach the required working concentration. The calculator can convert between mass concentration and molar concentration.
  • Calculate a volume adjustment to reach a desired final concentration.
  • Calculate a substance solution concentration from its absorbance and vice versa.

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Molarity, mass and volume

Definitions and explanations

The app can use a3132132132112345565989879846 tabular dataset or individual data lists as the input. In the first case, click the "Tabular Input" heading and provide the data. In the latter case, the required number of empty list forms has to be prepared up front. This can be done by filling the number of lists to be prepared in the "Number of lists" field followed by clicking the "Set" button (all existing lists will be discarded). To add a list form to an existing set of forms, click the large plus button located just after the last list form.

To apply any changes made in the settings or in input data, click the "Compare" button.

Calculations

To apply any changes made in the settings or in input data, click the "Compare" button.

Close

Percentage and molarity

Definitions and explanations

The app expects an input in the form of simple item lists i.e. with one item per line. If the source data are to be loaded from files, the files should be plain text files (no formatting) containing one item per each line or comma-separated items.

Calculations

To apply any changes made in the settings or in input data, click the "Compare" button.

Close

Dilution of a stock solution to a working concentration

Definitions and explanations

The app can import a tabular dataset wherein the list items are organized column-wise and separated with delimiters in each row. The delimiter can be one of the characters tab, comma or semicolon and has to be properly chosen before reading the data into the app with the "Read Data" button. You can directly copy - paste data from Microsoft Excel or other spreadsheet programs. Choose tab as the delimiter in such cases. If the source data are to be loaded from a file, the file should be a plain text file containing delimiter-separated values. After clicking the "Read Data" button, the values should get properly distributed into individual input lists. If not, check the delimiter choice and appearance of the data. The problem may also be caused by a presence of additional text lines preceding the data. Such lines have to be removed manually.

Calculations

To apply any changes made in the settings or in input data, click the "Compare" button.

Close

Dilution to a desired concentration

Definitions and explanations

The app expects an input in the form of simple item lists i.e. with one item per line. If the source data are to be loaded from files, the files should be plain text files (no formatting) containing one item per each line or comma-separated items.

Calculations

To apply any changes made in the settings or in input data, click the "Compare" button.

Close

Absorbance of a solution

Definitions and explanations

The app can import a tabular dataset wherein the list items are organized column-wise and separated with delimiters in each row. The delimiter can be one of the characters tab, comma or semicolon and has to be properly chosen before reading the data into the app with the "Read Data" button. You can directly copy - paste data from Microsoft Excel or other spreadsheet programs. Choose tab as the delimiter in such cases. If the source data are to be loaded from a file, the file should be a plain text file containing delimiter-separated values. After clicking the "Read Data" button, the values should get properly distributed into individual input lists. If not, check the delimiter choice and appearance of the data. The problem may also be caused by a presence of additional text lines preceding the data. Such lines have to be removed manually.

Calculations

To apply any changes made in the settings or in input data, click the "Compare" button.

Close