Question

Identify the solute and the solvent in each solution composed of the following: a. \(10.0 \mathrm{~g}\) of \(\mathrm{NaCl}\) and \(100.0 \mathrm{~g}\) of \(\mathrm{H}_{2} \mathrm{O}\) b. \(50.0 \mathrm{~mL}\) of ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), and \(10.0 \mathrm{~mL}\) of \(\mathrm{H}_{2} \mathrm{O}\) c. \(0.20 \mathrm{~L}\) of \(\mathrm{O}_{2}\) and \(0.80 \mathrm{~L}\) of \(\mathrm{N}_{2}\)

Short answer

a) NaCl is the solute, H2O is the solvent. b) H2O is the solute, ethanol is the solvent. c) O2 is the solute, N2 is the solvent.

Step-by-step solution

Define solute and solvent

A solution is a homogeneous mixture of two or more substances. The substance present in a greater amount is usually called the solvent, and the substance present in a lesser amount is the solute.

Identify solute and solvent in case (a)

In case (a), there is 10.0 grams of \(\text{NaCl}\) and 100.0 grams of \(\text{H}_{2} \text{O}\). Since \(\text{H}_{2} \text{O}\) is present in a larger amount, it is the solvent, and \(\text{NaCl}\) is the solute.

Identify solute and solvent in case (b)

In case (b), there is 50.0 mL of ethanol \(\text{C}_{2} \text{H}_{5} \text{OH}\) and 10.0 mL of \(\text{H}_{2} \text{O}\). Since ethanol is present in a larger amount, it is the solvent, and \(\text{H}_{2} \text{O}\) is the solute.

Identify solute and solvent in case (c)

In case (c), there is 0.20 L of \(\text{O}_{2}\) and 0.80 L of \(\text{N}_{2}\). Since \(\text{N}_{2}\) is present in a larger amount, it is the solvent, and \(\text{O}_{2}\) is the solute.

Key concepts

Solute

The solute is the substance that gets dissolved in a solution. Think of it as the 'minor ingredient' in the mixture. Let's compare it to making lemonade. If you mix sugar into the lemon water, the sugar is the solute. It gets spread out evenly throughout the liquid.
In everyday life, you see solutes in many forms. For example:

• Sugar in tea
• Salt in seawater
• Carbon dioxide in soda

Solutes are typically found in a smaller amount compared to the solvent. This brings us to our next topic, the solvent.

Solvent

The solvent is the substance that dissolves the solute. It is often present in a larger amount and serves as the 'main ingredient' of a solution. Using the lemonade example, the lemon water is the solvent where the sugar (solute) gets dissolved.
Common examples of solvents include:

• Water, often called the 'universal solvent'
• Alcohol, used in tinctures and solutions
• Acetone, used in nail polish remover

Solvents can be liquids, gases, or solids but liquids are the most common. The nature of the solvent determines many properties of the solution, such as its boiling and freezing points.

Homogeneous mixture

A solution is also known as a homogeneous mixture. This means that the mixture is uniform throughout. Once the solute is dissolved, you cannot easily separate it from the solvent. Going back to our lemonade example, after the sugar dissolves in the lemon water, it forms a homogeneous mixture.
These mixtures have consistent properties and appearance throughout. Some everyday examples include:

• Tea sweetened with sugar
• Air, which is a mixture of various gases
• Alloy metals like steel, which is a mix of iron and carbon

In homogeneous mixtures, every sample taken from the mixture will have the same proportion of components.

Solute Identification

Identifying the solute in a solution is straightforward. It's the component that is present in the lesser amount and gets dissolved. Let's look at some practice problems to see how this works:

a. In a mixture of 10.0 grams of NaCl and 100.0 grams of H₂O, the NaCl (salt) is the solute because it is present in a smaller quantity.
b. For a mixture of 50.0 mL of ethanol and 10.0 mL of H₂O, the H₂O (water) is the solute for this particular solution.
c. In a combination of 0.20 L of O₂ and 0.80 L of N₂, the O₂ (oxygen) is the solute since it is present in a lesser volume.
Knowing the solute helps us understand the solution's properties and behavior.

Solvent Identification

Identifying the solvent in a solution follows similar principles. The solvent is the substance that is present in a larger amount, and it dissolves the solute. Let's revisit our practice problems:

a. With 10.0 grams of NaCl and 100.0 grams of H₂O, the H₂O (water) is the solvent because it is abundant.
b. For a solution with 50.0 mL of ethanol and 10.0 mL of H₂O, the ethanol is the solvent as it is in a greater amount.
c. In a mix of 0.20 L of O₂ and 0.80 L of N₂, the N₂ (nitrogen) is the solvent because it is present in more volume.
Identifying the solvent helps predict the solubility and interactions of the solution components.