1.

A solution of ethanol in water is 10% by volume. If the solution and pure ethanol have densities of 0.9866g//"cc" and 0.785g//"cc" respectively, find the per cent by weight.

Answer»

Solution :VOLUME of ethanol `=10mL`, VOL of soultion `=100ML`
WEIGHT of ethanol `=` volume `xx` density
`=10xx0.785=7.85g`
Weight of solution `=100xx0.9866=98.66g`
`:.` weight per CENT `=(7.85)/(98.66)xx100=7.95%`


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