Question

In each pair complete the following 3 parts;

      i) identify ALL the intermolecular forces present in each (ion-dipole; H-bonding; diploe-dipole; dispersion)

      ii) circle the substance in each pair with the higher boiling point

     iii) explain your choice for “ii”

                                                                                                                                                           in aqueous solution

a) CH₃Bror   CH₃F                     b) CH₃CH₂CH₂OH   or   CH₃CH₂OCH₃                     c) MgCl₂   or   SrCl₂  

i:                                                                 i:                                                                               i:

        

iii:                                                            iii:                                                                                iii:

Answer 1

FOR 1ST we have

1.ch3br and ch3f

type of bond :-ch3br(Dipole-dipole interactions and dispersion forces).

ch3f(dipole dipole becauseCH3F is a polar molecule, it has a permanent dipole. In this case hydrogen bonding does NOT occur, since the F atom is bonded to the central C atom (F must be bonded to H in order for hydrogen bonding to occur).

2. for boiling point we have ch3br having higher than ch3f.

3. reason :-

CH3Br is quite much more heavy molecule compared to CH3F. As CH3F does not form hydrogen bonds and a slight increase in polarity does not really have that large effect in the intermolecular forces. So the weight is the main factor.

Dipole-dipole is not as strong as you think, Br has a lot more electrons than F making the dispersion forces a LOT stronger..

FOR 2ND

CH3CH2CH2OH AND CH3CH2OCH3

1.CH3CH2CH2OH(h bonding) AND CH3CH2OCH3(dipole-dipole interactions,)

2.boiling point is higher in case of ch3ch2oh than ch3ch2och3 beacuse 1st having h bonding is quite higher than ether group having dipole dipole ineraction.

FOR 3RD

we have mgcl2 and srcl2 (both are ionic bond)

mgcl2 boiling point 1412` C AND Boiling point of srcl2 1250`c

beacuse mgcl2 having less electronic crowding than crcl2.