1.

Calculate the molarity and molarity of a solution of ethanol in water if the molre fraction of ethanol is 0.05 and the density of solution is 0.997 g/"cc"

Answer»

Solution :SINCE mole fraction of `C_(2)H_(5)OH=("MOLES of " C_(2)H_(5)OH)/("moles of" C_(2)H_(5)OH+"moles of " H_(2)O)`
`=0.05=(5)/(100)`
`:.100` moles of solution contain 5 moles of `C_(2)H_(5)OH`
Weight of `C_(2)H_(5)OH=` moles `xx`mol.wt.
`=5xx46=230g`
Weight OG `H_(2)O=95xx18=1710g`
`:.` weight of solution `=230+1710=1940g`
Volume of solution `=(1940)/(0.997)"cc"=1945.8mL=1.9458` litres
`:.` molality `=(5)/(1710)xx1000=2.92m`
Molarity `=(5)/(1.9458)=2.57M`


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