delta T = Kf*m
You know delta T and Kf (1.86 for water), calculate molality.
molality = mols/kg.
You know molality and kg, solve for moles.
mols = grams/molar mass
You know mols and molar mass, solve for grams. Post your work if you get stuck.
what mass of ethylene glycol C2H6O2 the main component of anitfreeze, must be added to 10.0L water to produce a solution for use in a car's radiator that freezes at -23.3°C. Assume the density for water is exactly 1 g/m.L
5 answers
I feel like I have made a mistake because the mass seems too small. I don't know where I went wrong :S
Molality = ÄTf / (Kf * i)
= 23.3°C / (1.86°C/m * 3)
= 4.18m (mol C2H6O2 / kg water)
The amount to dissolve is:
n_C2H6O2 = molality * m_water
= 4.18 mol/kg * 0.1kg
= 0.0418 mol
m_C2H6O2 = n_C2H6O2 * M_C2H6O2
= 0.0418mol * 62g/mol
= 2.59g
Molality = ÄTf / (Kf * i)
= 23.3°C / (1.86°C/m * 3)
= 4.18m (mol C2H6O2 / kg water)
The amount to dissolve is:
n_C2H6O2 = molality * m_water
= 4.18 mol/kg * 0.1kg
= 0.0418 mol
m_C2H6O2 = n_C2H6O2 * M_C2H6O2
= 0.0418mol * 62g/mol
= 2.59g
Let's see. Why are you using i. i is the van't Hoff factor which is 1 for ethylene glycol.
delta T = Kf*m
23.3 = 1.86*m
m=23.3/1.86 = 12.527 molal.
m = mols/kg solvent
12.527 = mols/10 kg = 125.27 moles.
grams = mols x molar mass = 125.27 x 62.068 = 7,775.18 g ethylene glycol. You need to redo the problem and straighten the significant figures out. I usually carry one more than I'm allowed, then round at the end. I think 23.3 is the most s.f. and 1.86 both have 3 places, so the answer would round to 7.78 x 10^3 grams . Check my work.
delta T = Kf*m
23.3 = 1.86*m
m=23.3/1.86 = 12.527 molal.
m = mols/kg solvent
12.527 = mols/10 kg = 125.27 moles.
grams = mols x molar mass = 125.27 x 62.068 = 7,775.18 g ethylene glycol. You need to redo the problem and straighten the significant figures out. I usually carry one more than I'm allowed, then round at the end. I think 23.3 is the most s.f. and 1.86 both have 3 places, so the answer would round to 7.78 x 10^3 grams . Check my work.
I did it again this time I got 7774.51g which is much better. Thanks alot!
I don't understand why is it 10kg solvent?