Identify the yellow crystals seen in the first two videos. Lead nitratePotassium iodideLead iodidePotassium nitrate

The yellow crystals identified in the videos are most likely lead iodide. Lead iodide (PbI₂) is known for its distinct yellow color, especially when precipitated from a reaction involving lead ions and iodide ions. The formation of lead iodide typically occurs when solutions of lead(II) nitrate and potassium iodide are mixed. The reaction can be represented as:

$\text{Pb(NO}_3\text{)}_2 + 2\text{KI} \rightarrow \text{PbI}_2 (s) + 2\text{KNO}_3$

In contrast, lead nitrate and potassium nitrate are both soluble and do not form yellow crystals, while potassium iodide does not produce yellow crystals itself. Therefore, based on the description of yellow crystals seen in the videos, the most plausible identification is indeed lead iodide.