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Different Properties of Solutions Study Guide

How do solutes affect the properties of solvents? By lowering the freezing point and increasing their boiling point.

INTRODUCTION

When we dissolve a soluble solute in a solvent, the molecules of the solute move apart and become surrounded by the solvent molecules before entering into a solution. We can ensure complete solubility only when the intermolecular forces of solute and solvent are similar.

There are some ionic solutes that separate to form cations and anions when dissolved. This imparts an electric nature to the solution, and it starts behaving like a battery when supplied with an anode and cathode.

EFFECT OF SOLUTE ON THE SOLVENT

A solute is the substance that dissolves completely in another substance known as a solvent. When we add a solute to the solvent, it alters general properties of the solvent such as its freezing or boiling point.

These changes in property are respectively called freezing point depression and boiling point elevation. We know that the freezing point of pure water is 0°C. If you add salt to the water, you’ll notice that when allowing the water to freeze, it forms ice at a temperature lower than 0°C. Similarly, the water boils at a temperature higher than 100°C.

FREEZING POINT DEPRESSION

Freezing Point Depression Source

As discussed earlier, the boiling and freezing points of a solution change when we add a solute to it. This is why freshwater lakes freeze at 0°C, while the ocean water freezing point is -2.2°C.

We apply the principle of freezing point depression to melt ice during winters and clear roads. By adding salt over ice, we expedite the melting process. Similarly, those living in extremely cold conditions put a certain liquid known as antifreeze in their radiator to keep the engine running. The antifreeze lowers the temperature of the liquid present in the radiator.

As a result, the liquid doesn't freeze when the temperature drops to 0°C. Some antifreeze liquids don't allow the liquid to freeze even when the temperature goes below -37°C.

BOILING POINT ELEVATION

The property of boiling elevation has its advantages in certain situations. For example, people add salt to meat to cook it perfectly at higher temperatures. People who live in hot, dry climates experience extreme heat, and when they run their vehicle in such conditions, the temperature of the liquid in the engine rises above 100°C and starts boiling. This damages the engine and leads to a breakdown. Adding antifreeze helps with this too by ensuring that the liquid in the engine doesn't boil at 100°C and keeps the engine running, even when the temperature goes beyond 129°C.

CONCLUSION

  • When a solute comes in contact with a solvent, it alters the general properties of the solvent.
  • The observable change in property is that the freezing point of the solvent goes down, and the boiling point increases. These phenomena are known as freezing point depression and boiling point elevation, respectively.
  • Freezing point depression is also why freshwater lakes freeze at 0°C while the seas and the oceans freeze at -2.2°C.

FAQs

1. What is the relationship between solutes and solvents?

A solute alters the general properties of the solvent when it interacts with the solvent.

2. What are the effects of solute on a solution?

A solute generally lowers the freezing point of the solution or raises its boiling point. The phenomenon is termed freezing point depression and boiling point elevation, respectively. This is why the ocean freezing point is -2.2 degrees Celsius.

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SOURCES:

  1. Properties of Solutions: https://www.ck12.org/c/chemistry/freezing-point-depression/lesson/Properties-of-Solutions-MS-PS/. Accessed 5th March 2022.
  2. Properties of Solutions: https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Chemistry_-_The_Central_Science_(Brown_et_al.)/13%3A_Properties_of_Solutions.Accessed 5th March 2022.