---
title: "A student investigates three chemical processes used to treat different laboratory wastewater samples. The balanced chemical equations for the reactions are shown in the table below.  | Process | Balanced chemical equation | | :— | :— | | 1 | \\(\\text{Pb(NO}_3\\text{)}_2\\text{(aq)} + 2\\,\\text{KI(aq)} \\rightarrow \\text{PbI}_2\\text{(s)} + 2\\,\\text{KNO}_3\\text{(aq)}\\) | | 2 | \\(\\text{HNO}_3\\text{(aq)} + \\text{KOH(aq)} \\rightarrow \\text{KNO}_3\\text{(aq)} + \\text{H}_2\\text{O(l)}\\) | | 3 | \\(\\text{Zn(s)} + 2\\,\\text{HCl(aq)} \\rightarrow \\text{ZnCl}_2\\text{(aq)} + \\text{H}_2\\text{(g)}\\) |  Which species acts as the reducing agent in the oxidation-reduction reaction?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/119692/"
date_modified: "2026-08-21T08:12:03+00:00"
---

# A student investigates three chemical processes used to treat different laboratory wastewater samples. The balanced chemical equations for the reactions are shown in the table below.

| Process | Balanced chemical equation |
| :— | :— |
| 1 | \(\text{Pb(NO}_3\text{)}_2\text{(aq)} + 2\,\text{KI(aq)} \rightarrow \text{PbI}_2\text{(s)} + 2\,\text{KNO}_3\text{(aq)}\) |
| 2 | \(\text{HNO}_3\text{(aq)} + \text{KOH(aq)} \rightarrow \text{KNO}_3\text{(aq)} + \text{H}_2\text{O(l)}\) |
| 3 | \(\text{Zn(s)} + 2\,\text{HCl(aq)} \rightarrow \text{ZnCl}_2\text{(aq)} + \text{H}_2\text{(g)}\) |

Which species acts as the reducing agent in the oxidation-reduction reaction?

A student investigates three chemical processes used to treat different laboratory wastewater samples. The balanced chemical equations for the reactions are shown in the table below.

| Process | Balanced chemical equation |
| :--- | :--- |
| 1 | \(\text{Pb(NO}_3\text{)}_2\text{(aq)} + 2\,\text{KI(aq)} \rightarrow \text{PbI}_2\text{(s)} + 2\,\text{KNO}_3\text{(aq)}\) |
| 2 | \(\text{HNO}_3\text{(aq)} + \text{KOH(aq)} \rightarrow \text{KNO}_3\text{(aq)} + \text{H}_2\text{O(l)}\) |
| 3 | \(\text{Zn(s)} + 2\,\text{HCl(aq)} \rightarrow \text{ZnCl}_2\text{(aq)} + \text{H}_2\text{(g)}\) |

Which species acts as the reducing agent in the oxidation-reduction reaction?

- **A.** \(\text{Pb}^{2+}\text{(aq)}\) in Process \(1\)
- **B.** \(\text{OH}^-\text{(aq)}\) in Process \(2\)
- **C.** \(\text{H}^+\text{(aq)}\) in Process \(3\)
- **D.** \(\text{Zn(s)}\) in Process \(3\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119692/*