Sort the following from weakest to strongest, and explain Why briefly:
1.CFH2CO2H , CClH2CO2H
2.NH3 , CH3NH2 , (CH3)2NH , NF3

Hello 


1) The two acids listed here in order of strongest acid first
(rewritten to show the structures)  :


         O                                O
         ||                               ||
Fl - C - C - O - H        >      Cl - C - C - O - H 

the reason for the order has to do with the stabilization of the
conjugate base:
        O
        ||
R - C - C - O -   (negatively charged)

F is more electrophillic than Cl - therefore F stabilizes the negative
charge On the Carboxyl group through inductive effects through the
carbon backbone (Withdraws negative charge).


2) From strongest base to weakest base : (CH3)2NH, CH3NH2, NH3, NF3

the explanation here is much the same as above - inductive effects
through the backbone allow for stabilization of a positive charge on
the Nitrogen - methyl groups are slightly negative inductive donors
(Stabilizes positive Charge on N), whilst F withdraws electrons from
the N-thereby , making a positive charge on the N less stable.


References: 


Nice section on acids: 
http://www.chemguide.co.uk/basicorg/acidbase/acids.html

Nice Section on bases: 
http://www.chemguide.co.uk/basicorg/acidbase/bases.html#top
http://www.cm.utexas.edu/bauld/teach/acidsbases.html#str  (See section
on inductive effects)


Google search: "organic chemistry acids bases"