Question

Homework #1 (13) Problem 13.49 The density of acetonitrile (CHCN) is 0.786 g/mL, and the density of methanol (CH-OH) is 0.701 g/mL A solution is made by dissolving 21.5 mL CH,OH in 98.7 mL CH, CN What is the mole fraction of methanol in the solution? Undo riglo Pese keyboard shortcuts Help XCHOR Submit Previous Answers Request Answer X Incorrect: Try Again; 4 attempts remaining Part B What is the molality of the solution? Assuming CH, OH is the solute and CH, CN is the solvent Tempiates Symbols Undo rogo Teset keyboard shortcuts mohon = mol/kg Submit Resueat Answer Part C Assuming that the volumes are active what is the martyCH,OH the solution Templates Symbols und record keyboard shortcuts ne ME Submit

Answer 1

As Density = Mars - Volumen so we can calculate mass of methanol and acetonitrile by the expression or formula Mass = Density Volume 20 Density of CHCN 0.786 g/me Volume of CHCN = 99-7ml using o we get Mass of CH CN =(0.786 g/mt) & (98. 7 ) =77.58g Density of CHOH = 0.791 g/ml Volume of choH = 21.5 mL So Mass of chot (0.791 g/max (21.5mt) = 17.00 g Now we will calculate number of moles of chhot and Chen as they are required in the calculations of mole fraction, molality and molarity Number of Moles Mass Molar Mass.

Molar Mass of CHCN = 41.05 g/mol MoRay Мода Сң он - 52: очах So, No, of moles - Mass of CHEN ——- с аң, сл. Модал момец - -------- {By assing fresamsala23 No. of moles of CHCN = 17.58g ---- 41.0salmok = = 1.89 moles Also, o məkах «Сң,0м - Most соң — Molar mass of Chon 17:004 32.00g/mol = 0.53 moles. Part A Mole fraction solution is of given a component by the a in a formula. Mole fraction (X ) = Number of moles of A - Total moles of solution This using this formula we ha

Mole fraction of Methanol. Exten = No. of moles of chon No. of males of CHOH- - Ne of moles of Sky ) (Because total moles of comprise moles of crot and cohen both) This Xenon = 0.53 mol (0.53+ 1.89) mot 0.53 = 0.219 Part & - Molality of a solution is given by the formula: Molality = Number of moles of solute - mass of solvent in kg Since solute is choth So No. of moles of solute = o.s3 moles Solvent is CHaN and its mass is 77.589 - 77.58 g = 77.58 kg = 0.07758 kg (because I g = 1000g as I kilo(t)=1000. - so lg = 1/1000 kg) 1000 units

Thus, Molality of solution - Numbe er of mole N of males of CHOL Mass of chce in kg 0.53 mol = 0.07758 kg m on = 16.83 mol/ kg / Parte Molarity of solution is given by the Molarity Number of moles of solute - Volume of solution in L Again, solute is crot so number of moles of solute are 0.53 moles. Volume of solution volume of crzott Volume of CH₂ CN = 21.5 ml + 98.7 me = 120.2 mb. = 120.2 L = 0.1202 L 1000 (Because I 2 = 1000 ml so I ml = 1000 Thus Molarity of solution = - 0.53 mol 4.4 mol/L 0.1202L 14.4LM