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Topic: Need help knowing what to do for question #4  (Read 599 times)

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Offline xiaohiro

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Need help knowing what to do for question #4
« on: January 23, 2019, 01:30:53 AM »
a) How would you make an aqueous solution of ethylene glycol that would protect the cooling system of  your car from freezing to a temperature of -20C
b) What volume percent ethylene glycol would you use? If your car holds 6.5L of  coolant, what volume ethylene glycol and what volume of water would you use to exactly fill the cooling system of your car? The density of of ethylene glycol, CH2(OH)CH2(OH), is 1,11g/mL. Assume that the volumes of water and ethylene glycol are additive.
c) what is the boiling point of the solution? Why would ethylene glycol be added to the cooling system of a car in Houston?
« Last Edit: January 23, 2019, 02:05:38 AM by xiaohiro »

Offline sjb

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Re: Need help knowing what to do for question #4
« Reply #1 on: January 23, 2019, 01:42:45 AM »
1 - consider typing the question out to help searches and in case the hosting of the image changes

2 - what equations do you know that may help (anything that relates impurities, melting/freezing point changes?)?

Offline xiaohiro

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Re: Need help knowing what to do for question #4
« Reply #2 on: January 23, 2019, 02:05:58 AM »
 I know the freezing and boiling point formulas but im not sure where to start

Offline Enthalpy

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Re: Need help knowing what to do for question #4
« Reply #3 on: January 23, 2019, 06:35:53 AM »
It's quite possible that the question includes some data about the sensitivity of the melting and boiling points to the proportion of glycol, then use them, keeping an eye on molar versus mass versus volume proportions.

Though, these relations are far from linear. Outside education, the proper method would be to look for experimental curves, which are plentiful in this case. Also keep in mind, beyond the present question, that volumes are not additive, especially with alcohols and water, and that propylene glycol replaces often the toxic ethylene glycol.

Boiling: the question probably wants you to answer that, but glycol also increases the viscosity, which is important to lubricate the pumps. Car coolant fluids contain more additives, especially against corrosion, possibly for wetting, against foam, and so on.

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