Cigars are best stored in a “humidor” at 18C and 55% relative humidity. This means the pressure of water vapour should b

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Cigars are best stored in a “humidor” at 18C and 55% relative
humidity. This means the pressure of water vapour should be 55% of
the vapour pressure of pure water at the same temperature. The
proper humidity can be maintained by placing an aqueous solution of
glycerol, C3H5(OH)3 , inside the humidor. Calculate the
concentration of glycerol (in mass %) required to lower the vapour
pressure of water to the desired value. Assume ideal behaviour,
with glycerol as a nonvolatile component. MW glycerol = 92.09
g/mol.