4. consider the following equilibrium: hno2(aq) + h2o(l) ⇌ h3o+(aq) + no2-(aq)\nin which direction will the…

Explanation:

Step1: Analyze effect of adding NaOH

NaOH is a strong - base. It will react with (H_3O^+) in the solution. The reaction is (OH^-(aq)+H_3O^+(aq)\rightleftharpoons2H_2O(l)). When (H_3O^+) is consumed, according to Le - Chatelier's principle, the equilibrium (HNO_2(aq)+H_2O(l)\rightleftharpoons H_3O^+(aq)+NO_2^-(aq)) will shift to the right to replenish the (H_3O^+) that has been removed.

Step2: Analyze effect of adding (NaNO_2)

(NaNO_2) dissociates in water as (NaNO_2(s)\rightarrow Na^+(aq)+NO_2^-(aq)). This increases the concentration of (NO_2^-) in the solution. According to Le - Chatelier's principle, the equilibrium will shift to the left to reduce the excess (NO_2^-) concentration.

Step3: Analyze effect of adding HCl

HCl is a strong acid. It dissociates as (HCl(aq)\rightarrow H^+(aq)+Cl^-(aq)), and (H^+) will combine with water to form (H_3O^+). So the concentration of (H_3O^+) in the solution increases. According to Le - Chatelier's principle, the equilibrium will shift to the left to reduce the excess (H_3O^+) concentration.

Step4: Analyze effect of dilution

When the solution is made more dilute, according to Le - Chatelier's principle, the equilibrium will shift in the direction that produces more moles of particles. In this case, the right - hand side has 2 moles of ions ((H_3O^+) and (NO_2^-)) while the left - hand side has 1 mole of solute ((HNO_2)). So the equilibrium will shift to the right.

Answer:

A. The equilibrium will shift to the right because (NaOH) reacts with (H_3O^+), decreasing its concentration and the system tries to replenish it. B. The equilibrium will shift to the left because the addition of (NaNO_2) increases the concentration of (NO_2^-) and the system tries to reduce it. C. The equilibrium will shift to the left because (HCl) increases the concentration of (H_3O^+) and the system tries to reduce it. D. The equilibrium will shift to the right because dilution favors the side with more moles of particles.