Question

What is the effect on the concentrations of NO₂⁻, HNO₂, and OH⁻ when the following are added to a solution of KNO₂ in water:

a) Increase in NO₂⁻, increase in HNO₂, decrease in OH⁻
b) Increase in NO₂⁻, decrease in HNO₂, increase in OH⁻
c) Decrease in NO₂⁻, increase in HNO₂, increase in OH⁻
d) Decrease in NO₂⁻, decrease in HNO₂, decrease in OH⁻

Answer 1

Adding substances to a KNO2 solution affects the equilibrium between NO2-, HNO2, and OH-. HCl increases HNO2 while decreasing OH-, HNO2 increases its own concentration, NaOH increases OH- and NO2- while decreasing HNO2, and NaCl has no direct effect. Adding KNO can increase the concentration of NO2-. The correct option is a).

Step-by-step explanation:

When different substances are added to a solution of KNO2 in water, the concentrations of NO2⁻ (nitrite ion), HNO2 (nitrous acid), and OH⁻ (hydroxide ion) will be affected based on the principles of chemical equilibrium and acid-base reactions.

Adding HCl (hydrochloric acid) will increase HNO2 concentration due to the formation of nitrous acid from the reaction between HCl and NO2⁻. Consequently, the concentration of OH⁻ will decrease as H+ from HCl will react with OH⁻ to form water.

Adding HNO2 directly increases the concentration of HNO2 without initially affecting NO2⁻ or OH⁻.

Adding NaOH (sodium hydroxide) will increase the concentration of OH⁻ and thereby shift the equilibrium to produce more NO2⁻ while decreasing the concentration of HNO2.

Adding NaCl (sodium chloride) won't have a significant direct effect on the concentrations of NO2⁻, HNO2, or OH⁻, as NaCl is a neutral salt.

Adding KNO will potentially increase the concentration of NO2⁻, assuming KNO dissociates into K+ and NO2⁻ in solution. Option a) is the correct one.