Question

Nitric acid (hno3) is a strong acid that is completely ionized in aqueous solutions of concentrations ranging from 1% to 10% (1.50 m ). however, in more concentrated solutions, part of the nitric acid is present as un-ionized molecules of hno3. for example, in a 50% solution (7.50 m ) at 25°c, only 33% of the molecules of hno3 dissociate into h+ and no3–. what is the value of ka for hno3?

Answer 1

[HNO3]....... [H+] ........% ionization 
10.0 ........... 7.77 ....... 77.7% 
7.00............ 5.77 ....... 82.4% 
3.00 ........... 2.72 ....... 90.7% 
1.00 ........... 0.965...... 96.5% 
0.100 ......... 0.0996.... 99.6% 
0.0100........ 0.00999.. 99.9% 
0.00100...... 0.00100..100.0% 

HNO3(aq) <==> H+ + NO3^- ... Ka = ??? 
7.50M .............. 0....... 0 ........... initial 
3.02M .............. 2.48...2.48 ...... equilibrium, assuming that there is 33% ionization 

Ka = [H+][NO3-] / [HNO3] 
Ka = (2.48)² / 3.02 
Ka = 2.04