---
title: "A student models a selective precipitation step used to remove ions from a water sample. Solutions \\(\\text{X}\\) and \\(\\text{Y}\\) are prepared as shown.  | Solution | Composition | |———-|————-| | \\(\\text{X}\\) | \\(0.100\\ \\text{M KCl(aq)}\\) and \\(0.100\\ \\text{M Na}_2\\text{SO}_4\\text{(aq)}\\) | | \\(\\text{Y}\\) | \\(0.100\\ \\text{M Ba(NO}_3\\text{)}_2\\text{(aq)}\\) and \\(0.100\\ \\text{M Mg(NO}_3\\text{)}_2\\text{(aq)}\\) |  All compounds listed are soluble before mixing. At the experimental temperature, nitrate salts and salts containing alkali-metal cations are soluble. The chlorides of the cations present are soluble, and \\(\\text{BaSO}_4\\text{(s)}\\) is insoluble whereas \\(\\text{MgSO}_4\\text{(aq)}\\) is soluble. The student combines \\(25.0\\ \\text{mL}\\) of solution \\(\\text{X}\\) with \\(25.0\\ \\text{mL}\\) of solution \\(\\text{Y}\\). Assuming precipitation goes to completion, which precipitate is collected, and which ions are spectators in the net ionic equation?"
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url: "https://nerd-notes.com/ubq/120103/"
date_modified: "2026-08-21T08:41:37+00:00"
---

# A student models a selective precipitation step used to remove ions from a water sample. Solutions \(\text{X}\) and \(\text{Y}\) are prepared as shown.

| Solution | Composition |
|———-|————-|
| \(\text{X}\) | \(0.100\ \text{M KCl(aq)}\) and \(0.100\ \text{M Na}_2\text{SO}_4\text{(aq)}\) |
| \(\text{Y}\) | \(0.100\ \text{M Ba(NO}_3\text{)}_2\text{(aq)}\) and \(0.100\ \text{M Mg(NO}_3\text{)}_2\text{(aq)}\) |

All compounds listed are soluble before mixing. At the experimental temperature, nitrate salts and salts containing alkali-metal cations are soluble. The chlorides of the cations present are soluble, and \(\text{BaSO}_4\text{(s)}\) is insoluble whereas \(\text{MgSO}_4\text{(aq)}\) is soluble. The student combines \(25.0\ \text{mL}\) of solution \(\text{X}\) with \(25.0\ \text{mL}\) of solution \(\text{Y}\). Assuming precipitation goes to completion, which precipitate is collected, and which ions are spectators in the net ionic equation?

A student models a selective precipitation step used to remove ions from a water sample. Solutions \(\text{X}\) and \(\text{Y}\) are prepared as shown.

| Solution | Composition |
|----------|-------------|
| \(\text{X}\) | \(0.100\ \text{M KCl(aq)}\) and \(0.100\ \text{M Na}_2\text{SO}_4\text{(aq)}\) |
| \(\text{Y}\) | \(0.100\ \text{M Ba(NO}_3\text{)}_2\text{(aq)}\) and \(0.100\ \text{M Mg(NO}_3\text{)}_2\text{(aq)}\) |

All compounds listed are soluble before mixing. At the experimental temperature, nitrate salts and salts containing alkali-metal cations are soluble. The chlorides of the cations present are soluble, and \(\text{BaSO}_4\text{(s)}\) is insoluble whereas \(\text{MgSO}_4\text{(aq)}\) is soluble. The student combines \(25.0\ \text{mL}\) of solution \(\text{X}\) with \(25.0\ \text{mL}\) of solution \(\text{Y}\). Assuming precipitation goes to completion, which precipitate is collected, and which ions are spectators in the net ionic equation?

- **A.** \(\text{BaCl}_2\text{(s)}\) is collected; the spectator ions are \(\text{K}^+\text{(aq)}\), \(\text{Na}^+\text{(aq)}\), \(\text{Mg}^{2+}\text{(aq)}\), \(\text{SO}_4^{2-}\text{(aq)}\), and \(\text{NO}_3^-\text{(aq)}\).
- **B.** \(\text{BaSO}_4\text{(s)}\) is collected; the spectator ions are \(\text{K}^+\text{(aq)}\), \(\text{Na}^+\text{(aq)}\), \(\text{Mg}^{2+}\text{(aq)}\), \(\text{Cl}^-\text{(aq)}\), \(\text{NO}_3^-\text{(aq)}\), and \(\text{SO}_4^{2-}\text{(aq)}\).
- **C.** \(\text{BaSO}_4\text{(s)}\) is collected; the spectator ions are \(\text{K}^+\text{(aq)}\), \(\text{Na}^+\text{(aq)}\), \(\text{Mg}^{2+}\text{(aq)}\), \(\text{Cl}^-\text{(aq)}\), and \(\text{NO}_3^-\text{(aq)}\).
- **D.** \(\text{MgSO}_4\text{(s)}\) is collected; the spectator ions are \(\text{K}^+\text{(aq)}\), \(\text{Na}^+\text{(aq)}\), \(\text{Ba}^{2+}\text{(aq)}\), \(\text{Cl}^-\text{(aq)}\), and \(\text{NO}_3^-\text{(aq)}\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120103/*