a. Rank the following compounds from strongest to weakest intermolecular forces.

Question

a. Rank the following compounds from strongest to weakest intermolecular forces. For two compounds with the same dominant intermolecular force explain how you determined their relative IMF strength:

Water, Ethanol, 1-Propanol, Acetone, Pentane, Hexane

So I think that water and ethanol have hydrogen bonding, 1-propanol and acetone have dipole-dipole forces, and pentane and hexane only have london dispersion forces but how would I rank them among each other.

b. What are the relative rates of evaporation for these compounds? They would go in order from slowest to fastest by strongest to weakest bond strength yes?

Explanation / Answer

The strongest to weakest in order is

Water > ethanol 1-propanol > acetone > pentane > Hexane

Water is polar and has hydrogen bonding. Ethanol contains small portion of non polar ( i.e hydrcarbon) and polar. It also exbhibits hydrogen bonding. Hence 2nd in order. 1-Propanol has higher carbon count than ethanol. Hence relatively its non polar compared to ethanol. Hence 1-propanol is 3rd. Acetone is weakly polar hence 4th. Pentane is non polar with 5 carbon chain length while Hexane is non polar with 6 carbon chain length. Hence hexane is last due to higher non covalent character due to more hydrocarbons.

b) Rate of evaproation order is opposite of intermolecular force

Hexane > Pentane > acetone > 1-propoanol > ethanol > water

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