Silver nitrate (AgNO₃) combines first with chloride ions (Cl⁻) in water because silver chloride (AgCl) is much less soluble than silver chromate (Ag₂CrO₄).

Here's why:

* Solubility: Solubility refers to the maximum amount of a substance that can dissolve in a given solvent at a specific temperature.

* Formation of Precipitates: When a substance's solubility is exceeded, it precipitates out of solution as a solid.

* Relative Solubilities: AgCl is practically insoluble in water (very low solubility), while Ag₂CrO₄ is slightly soluble (meaning a small amount dissolves).

In a solution containing both Cl⁻ and CrO₄²⁻ ions, the following happens:

1. AgNO₃ dissociates: AgNO₃ dissolves in water, releasing Ag⁺ and NO₃⁻ ions.

2. AgCl formation: The Ag⁺ ions immediately react with Cl⁻ ions, forming solid AgCl, which precipitates out of solution due to its extremely low solubility.

3. Ag₂CrO₄ formation: The remaining Ag⁺ ions will then react with CrO₄²⁻ ions to form Ag₂CrO₄. However, since Ag₂CrO₄ is slightly soluble, a small amount will dissolve and remain in solution, while the rest precipitates out.

Therefore, AgCl forms first because its low solubility drives the reaction to completion, effectively removing Ag⁺ ions from the solution and preventing the formation of significant amounts of Ag₂CrO₄.