Selected Ions Forming Aqueous Solutions · Chemistry Reference Tables (2025 Edition)

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The Selected Ions Forming Aqueous Solutions table from the Reference Tables for Physical Science: Chemistry (2025 Edition) lists six ions whose compounds dissolve in water, with their formulas and charges. It primarily supports HS-PS1-10, and it also comes up in HS-PS1-2 (which products stay dissolved), HS-PS1-12 (spectator ions in net ionic equations) and HS-PS3-5 (how ions interact with water molecules).

What the selected ions table shows

These are the ions whose compounds are soluble in water whatever the other ion is: the Group 1 metal ions (Li⁺, Na⁺, K⁺, …), ammonium, acetate, chlorate, hydrogen carbonate and nitrate. A compound containing any of them dissolves to give a solution of mobile ions, and when such a compound is a product of a reaction in solution it stays dissolved rather than precipitating. The table also gives the formula and charge of the four polyatomic ions on it.

The 2011 edition of the Chemistry Reference Tables covered the same ground in more detail: Table F (solubility guidelines) listed these ions as forming soluble compounds and went on to give the halide and sulfate exceptions and the insoluble ions, Table G gave solubility curves, and Table E listed two dozen polyatomic ions. The 2025 edition keeps only this short list, so the formulas of other polyatomic ions (phosphate, sulfate, hydroxide, …) and any solubility data are supplied in the question cluster when they are needed.

Regents Exam Questions

Released Regents questions that cannot be answered without this table, listed by exam. Each link opens the question with its answer key; the standard is the one the question assesses.

Exam	Cluster	Question	Standard
August 2026 Chemistry Regents	Go With the Flow	Question 21	HS-PS3-5
	Pool Water Chemistry	Question 22	HS-PS1-2