Question

A student performed an experiment in which she combined potassium iodide with lead A student performed an experiment in which she combined potassium iodide with lead nitrate. She observed a yellow precipitate in the reaction. Formulate a possible inference that the student could make from the experiment.

A. A precipitate is an indicator of a chemical reaction and lead iodide is yellow, so a chemical reaction has occurred.
B. A precipitate is an indicator of a chemical reaction, so a physical change could have occurred.
C. A color change and a precipitate is an indicator that lead nitrate has rearranged its atoms, so lead nitrate is the only substance that has experienced a chemical reaction.
D. A color change is an indicator that a substance has changed state, so a change in state has occurred.

Answer 1

A yellow precipitate formed from the reaction of potassium iodide and lead nitrate indicates the chemical formation of solid lead iodide, demonstrating a double-replacement reaction.

Step-by-step explanation:

When a student combines a solution of potassium iodide with lead nitrate, the formation of a yellow precipitate indicates a chemical reaction. A precipitate is a solid that forms and settles out of a liquid mixture. Since lead iodide is known to be yellow in color, we can infer that lead iodide is the precipitate formed from the reaction between potassium iodide and lead nitrate. This is a result of a double-replacement reaction where the cations and anions from the two reactants combine to form an insoluble compound, lead iodide, and a soluble compound, potassium nitrate, which remains in solution.