Question

1. in what context do the terms hydrophobic and hydrophilic relate to the soulubilites of substance in water?
2. in each of the following pairs of compounds which compound is likely to be more souble in CC14?
(a) Br2 or NaBr
(b) CH3CH2OH or CH3OCH3
(c) Cs2 or KOH
(d) I2 or CaF2
3. which sulfur conpound would you predict to be more souble in nonpolar solvents: SO2 or CS2?
4. methanol has a larger molar mass than water, but boils at a lower temperature. Suggest a reason why?
5. How is it that the dipole moment of HCI(1.08D) is larger than the dipole moment of HBR (0.82D) yet HBR boils at a high temperature?
6. why is methanol miscible with water but methane is not?

Answer 1

1. in what context do the terms hydrophobic and hydrophilic relate to the soulubilites of substance in water?

water is "hydro" therefore, all substance ending in phobic, will not be miscible in water. The "philic" ending means "water loving" molecules, those will be soluble in water

2)

CC14 --- >you probably mean CCl4, since CC14 does not exist or makes sense in chemistry nomenclature

CCl4 is nonpolar, will mix better with nonpolar substances

(a) Br2 or NaBr - Br2 is nonpolar due to both poles canceling each other
(b) CH3CH2OH or CH3OCH3 - oonce again, both poles cancel each other

(c) Cs2 or KOH - CS2 is nonpolar, thereofe expect CCl4 better dissolution here
(d) I2 or CaF2 - As with Br2, I2 is nonpolar

3)

SO2 vs CS2... You need to calculate the electronegativity differences.

SO = 2.5-3.5 = -1 and CS2 = 2.5-2.5 = 0

Expect CS2 to be more NON polar, therefore better mix

4. methanol has a larger molar mass than water, but boils at a lower temperature. Suggest a reason why?

It does not bond strongly as water does with hydrogen bonding.

5. How is it that the dipole moment of HCI(1.08D) is larger than the dipole moment of HBR (0.82D) yet HBR boils at a high temperature?  

HBr boils at higher temperatures because the mass of HBr is way much higher, Br is a very large atom, therefore requires more energy to volatilize

6)

methanol is polar, methane is nonpolar. Water is polar and solubility rules state that polar-polar will mix