Foundation reading 13 of 17 · ~7 min
Describe solution concentration
Your goal: Relate moles of solute to the final solution volume in litres.
A focused reading from Molarity, Solution Preparation and Dilution. Reading time is a Chem Help estimate.
Optional prerequisite review
- Connect reactant mass to product mass
- Solutions, solute and solvent — foundation lesson missing
- Matter and measurement — foundation lesson missing
Review if useful. These suggestions never lock a step.
Defining molarity
Molarity, symbol M, equals moles of solute divided by litres of solution. The denominator is the total volume of the final solution, which is why solutions are made up to a mark rather than by adding a measured volume of solvent.
M = mol solute / L solution
Preparing a solution
To make 250.0 mL of 0.100 M NaCl, first find the moles needed, which is 0.2500 L x 0.100 mol/L = 0.0250 mol. Multiply by the molar mass to get 1.46 g.
Weigh that mass, dissolve it in less than 250 mL of water, transfer to a 250.0 mL volumetric flask, then add water to the calibration mark and invert to mix.
Sources and further reading
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