Question

Write your answer to each of the following questions, on the blanks at the left. C. Consider HN_O2 Its conjugate base is _____ HNO_2 is a _____ acid (strong or weak). In the reaction between HNO_2 and HCN: HNO_2(aq) + CN^-(aq) HCN(aq) + NO^-_2(aq) K = 1 times 10^6. The predominant species after the reaction reaches equilibrium are _____. (Write both species.) When HNO_2 is titrated with NaOH to the equivalence point, the pH of the resulting solution is _____ than, less than, equal to).

Answer 1

1) The conjugate base is the species which is formed by removal of H+. Thus conjugate base of HNO2 is NO2- .

2) HNO2 is a weak acid

3)since equilibrium constant is ratio of concentration of products to reactants. Since K= 10^6 . Thus products concentration is very high compared to reactants.

Thus predominant species at equilibrium are

HCN and NO2-

4) the reaction is:

HNO2 + NaOH -------> Na+ + NO2- + H2O

NO2- will undergo hydrolysis as follows

NO2- + H2O------> HNO2+ OH-

Thus OH- ions are produced, thus solution will be basic.

Thus pH will be greater than 7.