Skip to main content
Ch.13 - Solutions
Chapter 13, Problem 43

A KNO3 solution containing 45 g of KNO3 per 100.0 g of water is cooled from 40 °C to 0 °C. What happens during cooling? (Use Figure 13.11.)

Verified step by step guidance
1
Identify the solubility of KNO3 at the initial and final temperatures using the solubility curve provided in Figure 13.11. Solubility is typically given in grams of solute per 100 grams of solvent.
Calculate the initial concentration of the solution in terms of grams of KNO3 per 100 grams of water at 40 °C.
Compare the initial concentration to the solubility of KNO3 at 40 °C. If the initial concentration exceeds the solubility, the solution is supersaturated. If it is less, it is unsaturated.
Determine the solubility of KNO3 at the final temperature of 0 °C using the same solubility curve.
Compare the initial concentration of KNO3 to the solubility at 0 °C. If the initial concentration exceeds the solubility at 0 °C, precipitation will occur until the concentration matches the solubility at this temperature.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Solubility

Solubility refers to the maximum amount of a solute that can dissolve in a solvent at a given temperature and pressure. In the case of KNO3, its solubility decreases as the temperature drops, meaning that less KNO3 can remain dissolved in water at lower temperatures. Understanding solubility is crucial for predicting whether a solution will remain saturated or if precipitation will occur when cooled.
Recommended video:
Guided course
00:28
Solubility Rules

Saturation and Precipitation

A saturated solution is one where the maximum amount of solute has been dissolved in the solvent at a specific temperature. When a saturated solution is cooled, it may exceed its solubility limit, leading to precipitation, where the excess solute forms solid crystals. This concept is essential for understanding the changes that occur in the KNO3 solution as it cools from 40 °C to 0 °C.
Recommended video:
Guided course
01:53
Selective Precipitation

Cooling Effects on Solutions

Cooling a solution affects the kinetic energy of the molecules, which can lead to changes in solubility and the state of the solute. As temperature decreases, the solute's ability to remain dissolved diminishes, potentially resulting in crystallization. This principle is important for analyzing the behavior of the KNO3 solution as it transitions from a warmer to a cooler state.
Recommended video:
Guided course
01:17
Cooling Curve Example