Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040

  1. Calculate the Molarity of a Solution of Ethanol in Water in Which the Mole Fraction of Ethanol is 0.040 (Assume the Density of Water to Be One).
  2. Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040 (assume the density of water to be one). 


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Calculate the Molarity of a Solution of Ethanol in Water in Which the Mole Fraction of Ethanol is 0.040 (Assume the Density of Water to Be One).

Mole fraction of C 2H 5OH `=("Number of moles of ""C"_2"H"_5"OH")/"Number of moles of solution"` `0.040="n"_("C"_2"H"_5"OH")/("n"_("C"_2"H"_5"OH")+"n"_("H"_2"O"))`.......(1) Number of moles present in 1 L water:- `"n"_("H"_2"O") = (1000 " g")/(18 " g"" mol"^-1)` `"n"_("H"_2"O") = 55.55 " mol"` Substituting the value of `"n"_("H"_2"O")` in equation (1), `"n"_("C"_2"H"_5"OH")/("n"_("C"_2"H"_5"OH")+55.55)=0.040` `"n"_("C"_2"H"_5"OH") = 0.040 "n"_("C"_2"H"_5"OH") + (0.040)(55.55)` `0.96" n"_("C"_2"H"_5"OH") = 2.222 " mol"` `"n"_("C"_2"H"_5"OH") = 2.222/0.96" mol"` `"n"_("C"_2"H"_5"OH") = 2.314" mol"` ∴ Molarity of solution `=(2.314" mol")/(1 "L")` = 2.314 M

Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040 (assume the density of water to be one). 

Solution The mole fraction of ethanol is equal to the ratio of the number of moles of ethanol to the total number of moles present in the solution. For dilute solutions, 1 L of water (or 1 L of solution) contains $$\displaystyle \frac = 2.31 $$ moles. The molarity of the solution is the ratio of the number of moles of solute present in 1 L of solution. As 1 L of solution contains 2.31 moles of ethanol, the molarity of solution is 2.31 M.

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