---
title: "A student dissolves a sample of solid ammonium nitrate, \\(\\text{NH}_4\\text{NO}_3\\text{(s)}\\), in \\(100.0\\text{ g}\\) of distilled water in an insulated coffee-cup calorimeter. The initial temperature of the water is \\(22.0\\text{ }^\\circ\\text{C}\\), and the final temperature of the solution is \\(15.5\\text{ }^\\circ\\text{C}\\). Assuming the calorimeter absorbs negligible heat, which of the following correctly classifies the dissolution process and provides the correct justification?"
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/119663/"
date_modified: "2026-08-21T08:11:58+00:00"
---

# A student dissolves a sample of solid ammonium nitrate, \(\text{NH}_4\text{NO}_3\text{(s)}\), in \(100.0\text{ g}\) of distilled water in an insulated coffee-cup calorimeter. The initial temperature of the water is \(22.0\text{ }^\circ\text{C}\), and the final temperature of the solution is \(15.5\text{ }^\circ\text{C}\). Assuming the calorimeter absorbs negligible heat, which of the following correctly classifies the dissolution process and provides the correct justification?

A student dissolves a sample of solid ammonium nitrate, \(\text{NH}_4\text{NO}_3\text{(s)}\), in \(100.0\text{ g}\) of distilled water in an insulated coffee-cup calorimeter. The initial temperature of the water is \(22.0\text{ }^\circ\text{C}\), and the final temperature of the solution is \(15.5\text{ }^\circ\text{C}\). Assuming the calorimeter absorbs negligible heat, which of the following correctly classifies the dissolution process and provides the correct justification?

- **A.** It is exothermic because thermal energy is transferred from the system to the surroundings, causing the temperature of the solution to decrease.
- **B.** It is exothermic because thermal energy is absorbed by the surroundings from the system, resulting in a negative enthalpy change (\(\Delta H_{\text{soln}} < 0\)).
- **C.** It is endothermic because thermal energy is transferred from the surroundings to the system, causing the temperature of the solution to decrease.
- **D.** It is endothermic because thermal energy is transferred from the system to the surroundings, resulting in a positive enthalpy change (\(\Delta H_{\text{soln}} > 0\)).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119663/*