The molarity or molar concentration

 

 

 

The molarity or molar concentration

 

The following texts are the property of their respective authors and we thank them for giving us the opportunity to share for free to students, teachers and users of the Web their texts will used only for illustrative educational and scientific purposes only.

 

The information of medicine and health contained in the site are of a general nature and purpose which is purely informative and for this reason may not replace in any case, the council of a doctor or a qualified entity legally to the profession.

 

 

The molarity or molar concentration

 

MOLARITY

 

The molarity (or molar concentration) of a solution is the number of moles of solute dissolved in 1 L of solution.  It is expressed in moles per litre (mol/L, or M)

 

Molarity    =      amount of solute (in mol)

                        volume of solution (in L)

 

or:            C  =  n

                        V

 

Calculating Molarity – Example 1

 

Calculate the molarity of a solution that consists of 12.3 g of potassium nitrate dissolved in 50 ml of water.

 

Solution

 

First, you need to find the number of moles of potassium nitrate (KNO3).

 

M (KNO3)   =      39.10 + 14.01 + 3(16.00)

                =      101.11 g/mol

 

n      =      12.3 g

                101.11 g/mol

 

        =      0.1216 mol

 

Divide the number of moles by the number of litres.

 

50 ml/1000 = 0.050 L

 

C      =      0.1216 mol

                0.05 L

 

        =      2.43 mol/L

The molarity of the solution is 2.43 mol/L.

Example 2

 

Calculate the mass of NaCl required to prepare 250 ml of a 0.850 mol/L solution.

 

Solution

 

First you need to calculate the number of moles of NaCl, using the concentration and volume.

 

C = n/V     à     n      =      VxC

                               =      (0.250 L)(0.850 mol/L)

                               =      0.212 mol

 

M (NaCl)    =      22.99 + 35.45

                =      58.44 g/mol

 

m     =      (0.212 mol)(58.44 g/mol)

        =      12.4 g

 

p. 316  19-24

 

Source : http://taverner.wikispaces.com/file/view/MOLARITY.doc

Web site link: http://taverner.wikispaces.com

Google key word : The molarity or molar concentration file type : doc

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.

 

The molarity or molar concentration

Another Mole Concept: The Molar Concentration

 

Some Definitions you need to remember:

 

Solution:         homogeneous mixture of two or more substances.

Solvent:           the component of a solution that exists in greater quantity.

Solute:                    the component of the solution that exists in smaller quantity.

Concentration: amount of a substance present in a given volume of solution.

Concentrated:  has relatively large amount of substance present in a given volume of solution.

Dilute:             has relatively small amount of substance present in a given volume of solution.

 

Molar concentration or Molarity:       number of moles of a particular substance in one liter of solution.

 

Unit for Molarity:      “mole/L” or “M”

                                   1.0 M  is read as “ 1.0 MOLAR”

 

Symbol for concentration:                 [ ]        e.g.  [NaCl] = 1.2 M

 

The Formula for concentration:

 

Molar Concentration (c) =    moles (n)         c = molar concentration

                                               Volume (V)      n = number of moles

                                                                       V = volume, in litres

 

 

 

Source : http://www.msdiehl.com/resources/molar+concentration+notes.doc

Web site link: http://www.msdiehl.com

Google key word : The molarity or molar concentration file type : doc

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.

 

The molarity or molar concentration

 Molarity & Dilutions Notes

 

Concentration:  Measure of how much solute is dissolved in a specific amount of solvent/solution.

  • A concentrated solution contains larger amount of solute
  • A dilute solution contains a smaller amount of solute

 

Molarity (M):  moles of solute / liters of solution

  • Also know as molar concentration
  • It’s unit is M (read/pronounced a molar)

 

Example: 

1) What is the molar concentration of a liter solution with 0.5 mol of solute?

 

Molarity = moles of solute / liter of solution

              = 0.5 mol solute / 1 L solution

              = 0.5 M

 

  • A 100.5 mL IV solution containing 5.10g glucose (C6H12O6).  What is the molarity of the solution?  (MM of glucose = 180.16 g/mol)

 

Molarity = moles of solute / liter of solution

 

Step 1:  convert grams of solute glucose to moles solute using MM of glucose

5.10 g glucose x 1 mole glucose  = 0.0283 mol glucose

                    180.16 g glucose

 

Step 2:  convert mL of solution to Liters of solution

(Remember week 1 notes:  here we’re going from milliliters to liters so we’re going to a higher prefix this means we’re moving the decimal to the left 3 decimal places)

100.5 mL = 0.1005 L

 

Step 3:  solve for molarity

M = moles of solute/ liters of solution

    = 0.0283 mol glucose / 0.1005 L solution

    = 0.282 M

 

How to prepare a molar solution:

Given the desired molarity and volume you can mix a solution by:

Refer to example from class.

Also see p. 484 of text

 

 

 

 

Dilutions:  Adding additional solvent to dilute a more concentrated stock solution.

  • The total # of moles of solute does not change during a dilution (only solvent is added)

 

Dilution Equation:

M1V1 = M2V2

 

M1 = the initial molarity of the concentrated solution

V1 = the initial volume of the concentrated solution

M2 = the final molarity of the dilute solution

V2 = the final molarity of the dilute solution

 

Example:

What volume of 2.00 M CaCl2 stock solution would you use to make 0.50 L of 0.300 M CaCl2?

 

M1V1 = M2V2

 

M1 = 2.00 M

V1 = ?

M2 = 0.300 M

V2 = 0.50 L

 

2.00 M x V1 = 0.300M x 0.50L

V1 = 0.075 L

 

 

Source : http://chemistry2008.pbworks.com/f/Molarity+notes.doc

Web site link: http://chemistry2008.pbworks.com

Google key word : The molarity or molar concentration file type : doc

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.

 

The molarity or molar concentration

 

 

If you want to quickly find the pages about a particular topic as The molarity or molar concentration use the following search engine:

 

 

The molarity or molar concentration

 

Please visit our home page

 

Larapedia.com Terms of service and privacy page

 

 

 

The molarity or molar concentration