Question

In a 10.0 mL sample of potassium iodide solution, silver nitrate solution is added to produce silver iodide crystals. What is the purpose of adding an excess of silver nitrate solution?

a) Increase Reaction Rate
b) Precipitate Formation
c) Neutralization
d) Color Change

Answer 1

Adding an excess of silver nitrate solution to the potassium iodide solution ensures precipitate formation.

Step-by-step explanation:

The purpose of adding an excess of silver nitrate solution to the potassium iodide solution is to ensure precipitate formation. When silver nitrate reacts with potassium iodide, silver iodide crystals are formed, which are a yellow solid precipitate. Adding an excess of silver nitrate ensures that all of the iodide ions in the solution react with the silver ions, resulting in the maximum amount of silver iodide precipitate.

Answer 2

The purpose of adding an excess of silver nitrate solution is to ensure complete precipitation of silver iodide during the reaction. (option b)

Step-by-step explanation:

When silver nitrate is added to a potassium iodide solution, a precipitation reaction occurs, forming silver iodide. The balanced chemical equation for this reaction is:

`\[2AgNO_3 + 2KI \rightarrow 2AgI + 2KNO_3.\]`

Silver iodide (AgI) is sparingly soluble in water, meaning it can form a solid precipitate. To ensure that all the potassium iodide has reacted and that the maximum amount of silver iodide is formed, an excess of silver nitrate is added.

The stoichiometry of the reaction indicates that two moles of silver nitrate react with two moles of potassium iodide to produce two moles of silver iodide. By adding an excess of silver nitrate, we ensure that there are more than enough silver ions available to react with all the iodide ions, preventing the formation of any residual potassium iodide.

In analytical chemistry and qualitative analysis, this technique is employed to confirm the presence of certain ions in a solution, and the excess reagent ensures the completeness of the reaction, allowing for accurate determination.(option b)