Paul asks…
Can anyone help me solve this molality problem?
A 2.42 m solution of the solute diethyl ether dissolved in the solvent C4H8O is available. Calculate the mass (g) of the solution that must be taken to obtain 1470 g of (C2H5)2O.
weight loss cardiff answers:
Moles (C2H5)2O = 1470 g/74.123 g/mol=19.8
m = moles solute / Kg solvent
2.42 = 19.8 / Kg solvent
Mass solvent = 8.18 Kg
mass solution = mass solute + mass solvent = 8.18 +1.47 Kg=9.65 Kg
Maria asks…
How to determine lowest melting point?
So I have an exam coming up and I’d like to get some tips on how I can determine the lowest melting point. One of the questions I had on an exam before was:
Which if these should have the lowest mp temperature?
A) Diethyl ether
B) 2-methyl butane
C) N,N, Dimethyl ethylamine
D) Butyl amine
I know the answer is B, but how do we know that? Thanks in advanced =)
Awesome Aj! Thanks for your help =)
weight loss cardiff answers:
All of these compounds have London dispersion forces. LDF strength is respective to molar mass so the lower the molar mass, the lower the strength of the LDF and consequently the less energy is required to break the IMF and melt.
Steven asks…
How do you find a value for Kp?
You have 50mg of benzoic acid dissolved in 3mL of diethyl ether.This is extracted with 3mL of H2O.The ether layer is removed and dried yeilding 45mg of benzoic acid. What is the Kp value for the ether/water solution
weight loss cardiff answers:
Kp is partitioning coefficient: it is ratio of concentration in organic phase versus concentration in water phase. Since the volumes are the same in this experiment, we can take the ratio of masses: so Kp=45/5 = 9.
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