chemistry

posted by .

Okay so I know how I would normally determine molar mass of a compound *get out periodic table, sum up elements present, eg. H20 = [2(1.008)+16.00]g/mol*

But this is for a lab class and they want us to derive it.

Info found: Ethylene glycol (C2H6O2 according to book) dissolved in water:

mass water: 150 g
mass ethylene glycol: 50 g
found boiling point: 103 C

MW ethylene glycol: ?

We've been using the boiling point elevation equation a lot
^T(boil)=i*k(boil)*molality(m)

I suppose the molality would be:

1.) 50g solute*(1 mole solute/62.068g solute)=0.81 mol solute

2.) 150g solvent*(1 kg solvent/1000 g solvent)=0.150kg solvent

3.) m = 0.81 mol solute/0.150kg solvent
m = 5.4
van't Hoff factor of ethylene glycol is (I believe) 1 (organic compound)

this would make k(boil)=^T(boil)/m or more specifically ~0.74 (technically 20/27 but that would violate sig. figs)

but I'm not sure what any of this has to do w/ calculating the molecular weight.

Thank you in advance.

  • chemistry -

    delta T = Kb*m
    3= 0.512*m
    Solve for m

    molality = moles/kg solvent
    molality from above x 0.150 = moles ethylene glycol. Solve for moles.

    moles = grams/molar mass
    You have moles and grams, solve for molar mass. Assuming 103 is your best T measurment, I come up with about 57. The molar mass from the periodic table is about 62. Error about 8%.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    My question is what is the molar mass of 1.00 mol of Li?
  2. Chemistry

    When 23.18 g of element A react completely with 48.08 g of E, compound A2E is formed. When 11.70 g of A react with 22.57 g of G, compound AG is formed. If elements E and G react to form EG3, what mass in grams of G is required to react …
  3. chemistry help!!! (clueless)

    how do i find the mass number of chemicals I would think that you would add up the components masses (molecular masses [from periodic table) that make up the chemical... like...HCl (H= 1.008g/mol, Cl= 35.45g/mol) added= 36.458g/mol …
  4. Chemistry

    Maleic acid is an organic compound composed of 41.39% C, 3.47% H, and the rest oxygen. If 0.271 mol of maleic acid has a mass of 31.4 g, what are the empirical and molecular formulas of maleic acid?
  5. Science (Chemistry Periodic Table of Elements)

    A tube of "Brilliant Yellow" acrylic paint contains titanium dioxide. What transition metal is in this compound?
  6. Chemistry

    I did the work, but I need help checking it... A compound contains 83.24% by mass carbon. Calculate the molar mass of the compound if it contains 5 moles of carbon per mole of compound. This was my process: I took 100g of compound …
  7. honors chemistry

    Compare the present Periodic Table with Mendeleevs original Periodic Table in terms of how it is organized, number of elements, what it looks like, ease of understanding, and information given.
  8. Chemistry

    According to the Star Trek "Fifth Interstellar Geophysical Conference Standard" version of the periodic table, there are 140 known elements. In what group of the periodic table would you place element 117, "topaline" which is reported …
  9. Chemistry

    how do i figure out the valences for elements in the transition elements section in the periodic table of elements (i need it for doing nomenclature) and how do i figure out the valences if i don't have the periodic table of elements …
  10. Science

    The combustion of a compound which contains only C and H yields 2.58 g of CO2 and 0.53 g of H2O. What is the empirical formula of the compound?

More Similar Questions