Evaporation and Intermolecular Atractions A TABLE Substance! at (t1-t2) (°C) ol

Question

Evaporation and Intermolecular Atractions A TABLE Substance! at (t1-t2) (°C) ol ethanol 31 1-8 5 1-propanol Explanation At (c) 2-propanol t hasa gher mulecalor It has a kier r Qt110H | 1-butanol 125-5] | 2242 (10 poi it is p ndur bonds methanol t has a lowwer molecular wigth n-hexane -H vl 124.1214 041201811 >N> acetone r1,0 n-heptane 1-octanol PROCESSING THE DATA 1. Two of the liquids, n-pentane and 1-butanol, had nearly the same molecular weights, but significantly tho difference in At values of these substances, based on their

Explanation / Answer

6a) It is common knowledge that the stronger the intermolecular forces of attraction, the highest will be the change in temperature. Methanol shows the highest temperature change; hence, the alcohol with the strongest intermolecular force of attraction is methanol.

b) 1-hexanol shows the lowest temperature change followed by 1-octanol. 1-hexanol should have the weakest intermolecular force of attraction; however, we may assume both 1-hexanol and 1-octanol to have weak intermolecular forces of attraction.

c) All the alcohols can, in theory, exhibit hydrogen bonding. Hydrogen bonding is an intermolecular force of attraction (not an actual bond) between a positively polarized hydrogen atom of a X-H bond (X = N, O, F) and an atom Y (Y = N, O, F) of an adjacent molecule. Therefore, hydrogen bonding occurs only when hydrogen is attached to a highly electronegative atom like O and hence, all the alcohols can exhibit hydrogen bonding. Due to hydrogen bonding, the molecules can come close together and be associated via strong intermolecular forces. Methanol, being the smallest alcohol, exhibits the strongest hydrogen bonding and hence, the temperature difference is appreciably high.

1-hexanol is a large molecule and contains a cyclohexane ring. Bringing two cyclohexane rings close to each other via hydrogen bonding results in steric crowding. The destabilization caused by the two bulky cyclohexane rings outweighs the stabilization due to hydrogen bonding and hence, 1-cyclohexanol has the weakest hydrogen bonding and hence, the lowest temperature change.

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