Question

Calculate the molarity, molality and mole fraction of ethyl alcohol in a solution of total volume 95 mL prepared by adding 50 mL of ethyl alcohol (density `= 0.789 mL^(-1)`) to 50 mL water (density `= 1.00 g mL^(-1)`).

Answer 1

No. of moles of ethyl alcohol `= ("Vol." xx"density")/("Mol. mass")`
`= (50xx0.789)/(46)=0.8576`
No. of moles of water `= ("Vol."xx"density")/("Mol. mass")=(50xx1)/(18)=2.7777`
Molarity `= ("No. of moles")/("Vol. of sol. in mL")xx1000`
`=(0.8576)/(95)xx1000=9.027M`
Molarity `= ("No. of moles of solute")/("Mass of solvent in grams")xx1000`
`=(0.8576)/(50)xx1000=17.152m`
Mole fraction `= (0.8576)/(0.8576+2.7777)=(0.8576)/(3.6353)=0.236`.