Question

Please answer these question:

_ H2S is a stronger acid than phosphene ,PH3. What may you conclude about the strengths of their conjugate bases? Explain.

_Give examples of ions which can act as an acid or as a base, writing net ionic equations for each. Are they Amphiprotic or Amphoteric? Explain.

Answer 1

The conjugate base of weak acid is strong and the conjugate base of strong acid weak.

Therefore, The conjugate base(PH2-) of weak acid phosphene ,PH3 is strong

The conjugate base(SH-) of strong acid H2S, is weak

The examples of ions which can act as an acid or as a base are H2PO4^-, HPO4^2-, HSO4^-  

A pair of substances which differ by H+ ion are called conjugate acid -base pair.

The net ionic equations are

i) H2PO4^- -------> H+ + HPO4^{2-    acid base}

H2PO4^- + H+     ---------------> H3PO4              base    acid                                                               

ii) HPO4^2- ----------> H+ + PO4^{3-     
   acid base}                                                                                                                                                                                 

HPO4^2- + H+ ---------> H2PO4^-              

      base    acid                                                                                                                                                   

iii) HSO4^- + H+ ---------> H2SO4

   ^{acid base}            

    HSO4^- ---------------> H+ + SO4^2-

       base    acid           

Amphiprotic and Amphoteric are same

Amphiprotic solvents act both as protophilic or protogenic, e.g., water, ammonia, ethyl alcohol etc

H2O + H+ ---------------> H3O+                               H2O ------------------>   OH- + H+

base    acid              acid    base