Question

Consider the following equilibrium system: Evaluate each stress to determine if it will will result in an increase or decrease in the concentration of chromate ion, CrO42−​, as equilibrium is re-established Cr2​O72−​(aq)+3H2​O(l)⇌2CrO42−​(aq)+3H3​O+(aq) a) Addition of OH−ion. b) Concentrating the solution by allowing water to evaporate.

Answer 1

The addition of OH− ion to the equilibrium system will result in an increased concentration of CrO4−, while concentrating the solution by evaporation will decrease its concentration, according to Le Chatelier's principle.

Step-by-step explanation:

The addition of OH− ion and concentrating the solution by allowing water to evaporate are two stresses on an equilibrium system involving chromate ions. For the chemical equilibrium:

Cr2O7−​(aq) + 3H2O(l) ⇌ 2CrO4−​(aq) + 3H3O⁺(aq),

• a) Addition of OH− ion: The addition of OH− ion will remove H3O⁺ from the system by neutralizing it into water. According to Le Chatelier's principle, the equilibrium will shift to the right to compensate for the decrease in H3O⁺ concentration, resulting in an increase in the concentration of chromate ion, CrO4−.
• b) Concentrating the solution by evaporation: By concentrating the solution, you effectively increase the concentration of the dissolved species. Equilibrium will shift to the left, favoring the formation of reactants in this case, which will result in a decrease in the concentration of CrO4− ion.

This analysis relies on the principles of Le Chatelier, which predict how a system at equilibrium responds to disturbances or stresses.