Calculating Concentration

Concentration Formula and Calculations

The concentration of a solution is a measure of the number of particles of the solute, (a dissolvable solid) which is in the solvent, (the liquid in which the solute is dissolved). The concentration of a solution can vary based on whether the solution is concentrated or diluted.

 

The number of particles in a concentrated solution will be greater than the number of particles found in a diluted solution. For example, when a drink is sweetened by adding sugar. The more sugar that is added to the sweeter the drink will taste. This can be calculated by using two formulae and the accompanying formula triangles.

 

Finding the concentration of a solute is extremely important in order to determine the rate at which molecules will react to each other.

How to calculate Concentration

  • The first way of calculating is to use moles and mount the chemical substance and divide it by its volume. Here is the formula triangle for this:Most of the time volumes are measured in cubic centimeters. 1000 centimeter cubed ­= 1 decimeter cubed (1 liter)

    As an example:

    500 cubic centimeter = 0.5 decimeter cubed.

    1000 cubic centimeter = 1.0 decimeter cubed.

    1500 cubic centimeter = 1.5 decimeter cubed.

    2000 cubic centimeter = 2.0 decimeter cubed.

     

    If you are trying to find the value of any of the following three: Concentration (mol/decimeter cubed), Moles (mole), or Volume (decimeter cubed).
     

    1: In the case of concentration you can find the value by dividing the moles by the volume.

    E.g.: If you have 2 moles of salt and it is dissolved in 2 liters of water. What would the concentration be? 2 mol / 2 liters = 1 mole/decimeter cubed.
     

    2: In the case of the Mole you can find the value by multiplying the other values.
     

    3: The second way of calculating is very similar. However, in this case, we will use the mass of the substance divided by the volume in order to find the concentration instead of the mole of the substance.

    The formula is (mass/volume)(The concentration has the unit grams/decimeter cubed rather than moles/ decimeter cubed).
     

    E.g.: You have 10 gram/ decimeter cubed solution and must dissolve it to 250cc. What would the mass of salt need to be divided by? The answer is, 10g/ decimeter cubed x (250/1000)=2.5g.

Conclusion

In summary, there are two ways of calculating concentration. One involves moles of solute and one involves the mass of the solute. When calculating the concentration both ways will include dividing the volume. The formula triangle can be used to find any of the quantities by covering up the one you need to find and using multiplication or division of the two remaining quantities.

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