Dat Destroyer #87

[florida21]

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Which of the following produces highest freezing point (with all same moles) when dissolved in water?

a) HClO4
b) HClO3
c) HClO2
d) HClO
e) HCl


I am confused as to why you can't look at the ability to form intermolecular forces. HClO2 should be able to form more intermolecular forces and more London dispersion forces than HClO due to the greater size and the fact that there are 2 electronegative oxygens. Shouldn't this increase the FP and the MP together?

 

[DAT Destroyer]

Which of the following produces highest freezing point (with all same moles) when dissolved in water?

a) HClO4
b) HClO3
c) HClO2
d) HClO
e) HCl


I am confused as to why you can't look at the ability to form intermolecular forces. HClO2 should be able to form more intermolecular forces and more London dispersion forces than HClO due to the greater size and the fact that there are 2 electronegative oxygens. Shouldn't this increase the FP and the MP together?

The compound with the highest freezing point gives the fewest particles, therefore we most look for the weakest acid. HClO4 and HCl are strong acids and are quickly eliminated. For the remaining 3, see which acid is the weakest, if you recall for oxy acids, the weakest acid has the least amount of oxygens, namely HClO.

Hope this helps.

Dr. Romano

 

[florida21]

would you not use the rule that the molecule with the greatest molecular weight has the most london dispersion forces and therefore has the highest freezing and boiling point?