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Carol asks…

Predict which solvent will dissolve more of the given solute?

These are from one of my exams that I didn’t do so well in. Can you please explain this to me? I’m having a make-up test tomorrow. Thanks.

(a) Sodium chloride in methanol (CH3OH) or in propanol (CH3CH2CH2OH)

(b) Ethylene glycol (HOCH2CH2OH) in hexane (CH3CH2CH2CH2CH2CH3) or in water.

(c) Diethyl ether (CH3CH2OCH2CH3) in water or in ethanol (CH3CH2OH)

weight loss cardiff answers:

(a) Methanol – NaCl is ionic and will form ion-dipoles with the -OH groups of
both methanol and propanol. Propanol is less hydrophillic (water loving and
polar) to the dispersion forces to a greater extent.

(b) Water – Hexane has no dipoles and is non-polar. It will not interact with the
-OH groups in ethylene glycol. Water can H bond to the ethylene glycol.

(c) Ethanol – Diethyl ether can interact through a dipole and dispersion forces.
Ethanol can provide both while water would like to H bond.

Lisa asks…

Please help explain vapor pressure through the following calculation?

Diethyl ether has a DeltaH°vap of 29.1 kJ/mol and a vapor pressure of 0.703 atm at 25.0°C. What is its vapor pressure at 60.0°C?
final anwser should be in atm.

weight loss cardiff answers:

Clausius Clapyron equation:
ln(p1/p2) = (∆Hv/R) (1/T2 – 1/T1)
Just substitute (T in Kelvins)
ln(p1 / 0.703 atm) = [(29,100 J/mol) / (8.314472 J/K*mol)] (1/298 K – 1/333 K)
Solving, p1 = 2.42 atm.
The vapor pressure is above 1 atm 60.0 °C because the normal boiling point is 35 °C.

Mary asks…

You are busy carrying out an experiment when a classmate asks for your help.?

You are busy carrying out an experiment when a classmate asks for your help.
Your friend is holding up a reaction tube and seems confused about which layer is
aqueous and which is organic. You are in the middle of a different experiment
and you have no idea what is in the reaction tube. So you ask your friend about
the solvent he has used for his experiment. Your friend says he thinks he used
diethyl ether, but is not sure. He shows you the bottle from which he obtained the
solvent, but the label seems to be faded. What can you do to help your friend
solve the mystery about the aqueous and organic layers?

weight loss cardiff answers:

Mark the interface on the tube, add a little more solvent (or water) and see which layer gets bigger.
Works every time.

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Ken asks…

what type of the following solvents might be used to dissolve an oil stain?

water, diethyl ether, NaCl solution, CCl4, benzene

Thanks
Thank you so much Dr. buzz. You save my life. That answers is correct.

weight loss cardiff answers:

Patty,

Diethyl ether, CCl4, and benzene will dissolve oil stains (with effectiveness depending on the type of oil). The water and water with NaCl are too polar to effectively dissolve oil stains.

Hope that helped!

Donna asks…

Identify the classes of the following compounds?

CH3CH2CH2CH2COOH- Pentanoic Acid is a member of the amino acids class.
CH3CH -> <- CHCH2CH3- 2-Pentene is a member of the secondary alcohol class.
C2H5OC2H5- Diethyl ether is a member of the ether class.
CH3CH2CHOHCH2CH3- 3- Pentanol is a member of the primary alcohol class and is an organic compound.
(CH3)3 COH- 2-Propanol is a member of the secondary alcohol class and is also an organic compound.
CH3║CH is a member of the carboxylic acid class
I just want to check if I have this right, especially the last one. Thanks for the help!

weight loss cardiff answers:

Mostly wrong; learn them; get them right:

Carboxylic acid

Olefin

Ether

Secondary alcohol

Secondary alcohol

Alkane

l

Mark asks…

How do you do this chemistry lab problem?

The equation relating approximate barometric pressure (P, in torr) to altitude(h, in m) is at room T:

lnP = 6.63-(h8000)

Diethyl ether, CH3CH2OCH2CH3, a common organic solvent has a normal boiling point at 34.6 degrees C (and thus vapor pressure of 760 torr at 34.6 C). at 20 degrees C, it has a vapor pressure of 440 torr. At what approximate altitude will diethyl ether boil at 20 C? Where on the earth would it be a problem to keep this solvent liquid?

weight loss cardiff answers:

It looks like your pressure equation should read
ln(P) = 6.63 – h/8000
Then
h = 8,000(6.63 – ln(P))
When P = 440
h = 4,346 m (14,258 ft.)
This elevation is to be found on some of the higher mountain peaks and ranges.

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Robert asks…

what is the boiling point of diethyl ether using enthalpy of vapourisation and entropy?

diethyl ether ( C4 H10 O) has an ΔvapH of 28.36 kJ/mol and the phase change from liquid to gas has an ΔS° of 96.6 J/mol/K. what is the normal boiling point of diethyl ether?

weight loss cardiff answers:

At the normal boiling point, the liquid and gas phases of a material are in equilibrium. That means the free energy change for the reaction:

liquid -> gas

is zero.

You should also know that ΔG = ΔH – T*ΔS, so at equilibrium:

T = ΔH/ΔS

In this case, you are given the enthalpy and entropy of vaporization, so:

T_boiling = (28,360 J/mol)/(96.6 J/(mol*K)) = 294 K

John asks…

why is it better to use diethyl ether when performing trimyristin extraction from numeg instead of acetone or?

why is it better to use diethyl ether when performing trimyristin extraction from numeg instead of acetone or ethanol? does it have to do with the solubilities of trim. in each of these solvents? how would you rank trimyristin’s solubility in each of these solvents?

weight loss cardiff answers:

Hmm, i wonder why you’d want to do that?

Seriously though, i’d say it was to do with flammability and possibly toxicity, but that’s just a guess.

George asks…

When you add salicylic acid-naphthalene mixture in a diethyl ether with a saturated aqueous sodium bicarbonate?

When you add salicylic acid-naphthalene mixture in a diethyl ether with a saturated aqueous sodium bicarbonate solution, what kind of gas do they form?

weight loss cardiff answers:

CO2(g) is evolved…

Here’s the balanced equation.

C6H4(OH)-COOH (salicylic acid) + NaHCO3 (sodium bicarbonate) –> C6H4(OH)-COO-Na+ (sodium salicylate) + CO2 (carbon dioxide) + H2O

A wash with aqueous sodium barcarbonate solution is usually done to remove any unreacted acidic reagent (salicylic acid, in this case) from the reaction mixture. As you can see, salicylic acid reacts with sodium bicarb to form sodium salicylate, which is water soluble are therefore goes into the water layer. Meanwhile, the organic layer now only contains naphthalene, which can be recovered by evaporation of the diethyl ether solvent.

Hope this helps!!!

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Paul asks…

What is the boiling point of diethyl ether using enthalpy of vapourisation and entropy?

Diethyl ether ( C4 H10 O) has an ΔvapH of 28.36 kJ/mol and the phase change from liquid to gas has an ΔS° of 96.6 J/mol/K. what is the normal boiling point of diethyl ether?

weight loss cardiff answers:

At the normal boiling point, the liquid and gas phases of a material are in equilibrium. That means the free energy change for the reaction:

liquid -> gas

is zero.

You should also know that ΔG = ΔH – T*ΔS, so at equilibrium:

T = ΔH/ΔS

In this case, you are given the enthalpy and entropy of vaporization, so:

T_boiling = (28,360 J/mol)/(96.6 J/(mol*K)) = 294 K

Joseph asks…

What does diethyl ether do in the esterification of salicylic acid?

I’m writing a mechanism for the esterification of salicylic acid using thionyl cloride. Then water and diethyl ether. Then sodium bicarbonate.

I remember in lab that when the diethyl ether was added, it was just a washing process. But I don’t understand how it would fit into a mechanism.

Did it have a purpose? what did it chemically do to the molecule?

weight loss cardiff answers:

You need to give more info on what you did. Looking at your sketchy procedure there is stuff missing. What was the objective of the experiment. In any event, the diethyl ether would have been a wash solvent or an extraction solvent; it would not react under these conditions.

Charles asks…

Why is diethyl ether is more soluble in water than dihexyl ether?

Why is diethyl ether is more soluble in water than dihexyl ether? Would you expect propane or diethyl ether to be more soluble in water? Why?

weight loss cardiff answers:

That is because hexyl group is more NON-POLAR and bulky than ethyl group.. Giving much more repulsion to polar water molecule…

Hope I help you with that .. Goodluck and godbless!

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