Calculating Concentrations 1 Concentration of solutions

We have already discussed how to calculate masses of solids or volumes of gases, for the reactants or products in balanced equations. What if solutions are involved in the reaction An aqueous solution may be concentrated or dilute. That is, it may contain a large or small amount of solid dissolved in a given amount of water as shown in Fig. 9.1. 

It is common to measure the concentration of a solution in moles per cubic decimetre (mol dm ). For example, a solution of sodium chloride, of concentration 1 mol dm , contains 1 mol (or a mass of 23 + 35.5 = 58.5 g) of NaCl dissolved in 1 dm of solution. Always use the term solution and not water. A mixture of 58.5 g of NaCl dissolved in 1 dm of water is not quite the same thing. 

Different textbooks, according to their age and their country of origin, may express concentration as M (molar) or mol (moles per litre). Both these units maybe taken to mean the same as mol dm.  

When using this equation, volume is expressed in dm and concentration is in mol dm.  

Rearranged forms of this equation may be needed amount in mol 

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