4) Hydrogen bonds create the strongest intermolecular forces. Any hydrogen-oxyge
ID: 585585 • Letter: 4
Question
4) Hydrogen bonds create the strongest intermolecular forces. Any hydrogen-oxygen (H-O) bond will form them. Consider the formula C2HseO, which could represent ethanol (bp 78°C) or dimethyl ether (bp -11°C). Explain why their boiling points are so different, even though they contain the same atoms ethanol dimethyl ether H-C-C-O 5) When you add ice to your drink, the liquid water cools as the ice melts. The energy required to melt ice is 334 JIg, and you know that it takes 4.18 J to raise the temperature of one gram of water by 1°C. When one gram of water COOLS by 1°C, it transfers 4.18 J to something else, in this case, the ice. Assuming you add 25.0 g of ice to 200 mL of water at 20'C, what will the final temperature of your drink be?Explanation / Answer
4) Ethyl alcohol (CH3CH2O-H) and dimethyl ether (H3C-O-CH3) have same molecular formula but they are different structurally.
In ethyl alcohol, hydrogen atom connected to more electronegative element oxygen to form hydrogen bonds. The hydrogen attached to the oxygen will have a partial positive charge and oxygen partial negative charge. When two ethanol molecules come together, the partial positive hydrogen atom will be attracted by the partial negative oxygen atom and hydrogen bond is formed. Hydrogen bonds create stronger intermolecular force, which need more energy input in order to break .Beside hydrogen bonding, ethyl alcohol also has dipole-dipole forces and London dispersion forces, so ethanol have higher boiling point.
In dimethyl ether, the oxygen is attached to methyl groups. So there is no hydrogen bonding. Dimethyl ether has only dipole-dipole forces in addition to the London dispersion forces. Thus the boiling point of dimethyl ether is low.
5) Energy needed to melt the ice to liquid and then bring the liquid to final temperature.
Heat absorbed by ice cube = (25g )(334J/g) + 50g*4.184JC^-1 g^-1 (final temperature -0)
Heat absorbed by ice cube = 8350 J + 209.2 T = 8559.2 T
Heat released by liquid water = (200g)(4.184JC^-1^-1)(Final Temperature - 20 degrees C)
Heat released by liquid water = 836.8 T
Heat absorbed + Heat released = 0
T = 8559.2/836.8 = 10.2oC
Final temperature of drink will be 10.2oC
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