Question

Question 3

A)   First consider the types & strengths of IM forces in each liquid substance then arrange them according to the property.
                  
(i)   Arrange in order of decreasing (highest to lowest) surface tension.
                

a. CH3CH2CH2OH

b. HOCH2CH(OH)CH2OH

c.HOCH2CH2OH

                                                                                                                                          
(ii) Arrange the liquids in order of increasing (lowest to highest) evaporation at a given temperature.

a. C3H8 (propane)

b. C10H22 (dodecane)

c. C6H14 (hexane)

B) Why does antifreeze ingredient ethylene glycol (HOCH₂CH₂OH; MM = 62.07 g/mol) have a boiling point of 197.6 ^oC, whereas propanol (CH₃CH₂CH₂OH; MM = 60.09 g/mol) a compound with a similar molar mass, has a boiling point of only 97.4 ^oC? Explain being sure to mention the types of IM forces in both liquids.

Answer 1

A)

i)

CH3CH2CH2OH --> OH favours dipole formation + hydrogen bonding

HOCH2CH(OH)CH2OH --> propylen gylocol, high OH bonding

HOCH2CH2OH --> ethylene gylcol

therefore, choose B > C > A

ii)

evaporation..

propane --> very low, no hydrogn bond

dodecane --> highes, due to mass

hexane --> meddium

B)

ethylene glycol interacts readily with water, so it increases the Boiling/Melting points

for propanol, the molar mass is much lower, and melting point is also lower.... so this will not favour water's boiiling point... therefore it decreases