Solution Concentration

For chemical reactions that take place in solution the chemist needs to express the amount of material (solute) in a given amount of dissolving material (solvent). Generally, concentration is the ratio of the amount of solute to amount of solvent. There are several ways to express concentration. We will examine the most common ones used in chemistry.


Molarity is define as the number of moles of solute per liter of solvent.


What is the Molarity of a solution prepared by dissolving 8.0 grams of NaOH in H2O so that the final volume is 250 ml?

First convert grams to moles:

Then calculate the molarity
  • Determine Molarity from Mass and Volume:
  • Determine Moles from Volume and Molarity:
  • Determine Mass from Molarity and Volume:
  • Determine Volume from Molarity and Mass:
  • Calculate Molarity - Interesting Substances:
  • Calculate Molarity from Mass and Volume:
  • Calculate Molarity from Percentage and Density:
  • Calculate Number of Moles in Sample:
  • Calculate Mass in a Sample:

Mass Percent

Another way to express concentration is using Mass Percent.


Calculate the the mass percent of ethanol in a solution prepared by mixing 1.00 g of ethanol C2H6O with 100.0 g of H2O.



Often times solutions of a given concentration are prepared by diluting solutions of higher concentration. Here's an example of how to calculate how much a concentrated solution needs to be diluted to prepare a given concentration.

How many milliliters of 16 M HNO3 must be used to prepare 1.0 liters of a 0.10 M HNO3 solution?


So 6.2 ml of 16 M HNO3 diluted to 1 liter will give 0.10 M HNO3.

  • Dilution of Solutions:
  • Determine Mass of Solution Required Given % and Density:
  • Determine Volume of Solution Required Given % and Density:
  • Calculate Final Molarity from Molarity After Dilution:
  • Calculate Volume of Solution Required from Molarity:
  • Calculate Final Molarity from % and Density:

Homework from Chemisty, The Central Science, 10th Ed.

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