In an experiment with 320 mL of water, you add 48 grams of ethylene glycol. You

Question

In an experiment with 320 mL of water, you add 48 grams of ethylene glycol. You determine experimentally that the??Tf = 4.84oC. Showing all your work, use this information and the equation on slide 21 of Chapter 12, to calculate the number of moles of ethylene glycol that are present in the mixture. Assume you are not given the molar mass of ethylene glycol, what is your calculated molar mass from your experiment and the % error from the actual molar mass of ethylene glycol. (This is the point of experiment number 2 that you are doing this week in lab---you determine the molar mass of the solute dichlorobenzene from the experiment of freezing point depression in the solvent cyclohexane).

Explanation / Answer

Tf = Kf * m

Tf is the change in freezing point of the solvent,

Kfis the molal freezing point depression constant

m is the molal concentration of the solute in the solution.

let M be the molar mass of ethylene glycol

here molality of solution is=(48/M) /0.320

Kf=1.86 degrees C/m

Tf = 1.86 * 150/M = 4.84oC --------------------- (given)

= 57.64 gram

but actual molar weight of ethylenr glycol is 62 gram

so % error =( 62-57.64)*100/62 = 7.03%

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.