How to find molarity of ethylene glycol?

Question

If the density of a 40% mass solution of ethylene glycol in water is 1.0514 g/mL, at 20 degrees C, what is the molarity?

Ok, so I researched and found that ethylene glycol is C2H6O2, which when I calculated, resulted in a molar mass of approximately, 62.08g/mol.

Now, should I multiply

62.08g/mol x 1.0514 g/ml x 1000ml/1L x .4

I think I am approaching this incorrectly...any ideas what I am doing wrong?

I tried
1.0514g/ml * 1000ml/l= 1051.4 g/l
molar mass= 62.08g/mol
.4 * 1051.4= 420.56
so,
62.08 g/mol / 420.56 g/L = .148M
is this right?

Answer 1

One clue while setting up your equation... is ...

since its MOLARITY...your final goal is to get an answer in moles /Liter(i mean the unit)..right?

So, (g/ml)/(g/mol) , is gonna cancel out the gms, so you have mol/ml and then finally you convert the mls into liters, and get an answer in mols/liter. so (mol/ml)/ (L/ml)= mols/Liter....

Answer 2

That's nearly correct Rebecca ! C'mon it's easy, follow me !

Your solution weight 1051.4 g/L
40% in weight of it is your ethylene glycol.
So 1051.4*0.4= 420.56g of ethylene glycol !!
Now you have to divide, and not multiply your molar mass, you want your molarity no ?
So 420.56g/62.08g/L = 6.77 M

Have fun with the rest of your homework. LOL