Practical investigations
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Hello, I am currently doing my A2 project and am using distillation to find the alcohol content of wine. My experiment is based on Derek Denby's article and I do not understand why I am calculating the density. Can't I just calculate the concentration from the volume and mass of the ethanol?
What is the relationship is between concentration and density? Thanks.
Igloo writes ...
If you knew the “mass” of ethanol present in a given “volume” of solution, then yes, you would be able to calculate its concentration, but how are you proposing to do this? In practice there is no easy or obvious way of determining the mass of ethanol present. However, it is certainly possible to weigh the mass of solution occupying a known volume and this enables you to calculate the density of the mixture. Next you need to use a standard table of data to convert this density into a concentration.
Such a table applies to mixtures of water and ethanol at 20 °C. The rows taken in conjunction with the columns give the percentage of ethanol in grams per 100 grams of aqueous solution, and the values in the boxes are the densities of the aqueous solutions in g cm-3. Thus, for example, a solution found to have a density of 0.9431 g cm-3 at 20 °C must contain 36% ethanol.
Risk assessment
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updated: 14 October 2007
