2. Suppose that you were given a mixture of sand, iodine, sodium chloride, and n
ID: 714615 • Letter: 2
Question
2. Suppose that you were given a mixture of sand, iodine, sodium chloride, and n-pentane to separate. Using the information gathered on these and similar compounds in this experiment, and using what you know about the properties of these materials from other contexts, outline a procedure that could be used to do a quantitative separation of these four materials 3. The compounds dimethyl ether and ethanol have the same molecular formula, C2H&O. (That is, they are isomers of one another.) Their normal boiling points are significantly different, however, with one boiling at-23.6 °C and the other boiling at 78.5 °C. Show the structures of these two compounds and explain, in terms of their structures and the resulting intermolecular forces, why these two isomers boil at such different temperatures. Which isomer has which boiling point?Explanation / Answer
2 Ans.
Sand and sodium chloride (NaCl) do not dissolve in n-pentane. Iodine will be dissolved in n-pentane.
Sand and NaCl can be separated from iodine and n-pentane by filtration.
To the mixture containing sand and NaCl, add water which will dissolved the NaCl. Then, filter it to get NaCl solution as filtrate. Heat the NaCl solution which has water and NaCl to evaporate the water. The remaining solid after evaporation is the NaCl.
The sand is washed several times with water and then dried.
Iodine and n-pentane mixture can be separated by distillation. Distill the n-pentane and iodine mixture to recover iodine (solid) and condense the vapor of n-pentane to get liquid n-pentane.
3 Ans.
The structural formula of dithyl ether is CH3-O-CH3 and that of ethanol is CH3-CH2-OH
In ethanol, there is a H which is directly attached to an electronegative atom O. So, ethanol can easily form intermolecular hydrogen bonding with another ethanol molecule. This intermolecular hydrogen bonding binds ethanol molecules together.
Whereas, in dimethyl ether, although there is an O atom, there is no hydrogen which binds directly to O atom. The O atom is attached directly to two C atoms. Therefore, there is no hydrogen bonding. So, it is easier to separate dimethyl ether molecules from each other because of which it has lower boiling point than ethanol.
The boiling point of dimethyl ether is lower (-23.6 degree Celsius).
The boiling point of ethanol is higher (78.5 degree Celsius).
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