Question

Describe solvents and solutes in an aqueous solution.

Short answer

In an aqueous solution, water acts as the solvent, which is a substance that dissolves another substance called the solute, forming a homogenous mixture. Solutes can be gases, liquids, or solids, and their solubility in aqueous solutions depends on factors such as polarity, temperature, and pressure. Polar solutes generally dissolve better in aqueous solutions due to the "like dissolves like" principle, where they interact with the polar water molecules. The concentration of an aqueous solution describes the amount of solute present in a given volume or mass of the solvent, and can be expressed in units such as molarity, molality, or mass percent.

Step-by-step solution

Definition of Solvent

A solvent is a substance that dissolves another substance, called the solute, to form a solution. In the case of an aqueous solution, the solvent is always water.

Definition of Solute

A solute is a substance that is dissolved by a solvent to form a homogenous mixture, called the solution. Solutes can be gases, liquids, or solids.

Characteristics of Aqueous Solutions

An aqueous solution is a type of solution in which water acts as the solvent. Water is considered a universal solvent due to its polar nature, which allows it to dissolve a wide variety of substances. The solutes in an aqueous solution can include gases (e.g., oxygen, carbon dioxide), liquids (e.g., ethanol, acetic acid), and solids (e.g., table salt, sugar).

Polar and Nonpolar Solutes

In aqueous solutions, polar solutes typically dissolve better than nonpolar solutes. This is because of the "like dissolves like" principle, where polar solutes will interact with the polar water molecules, and nonpolar solutes will not interact as strongly with the water molecules.

Factors Affecting Solubility

There are several factors that affect the solubility of a solute in an aqueous solution, including temperature, pressure, and the presence of other solutes. In general, an increase in temperature will increase the solubility of a solid solute in an aqueous solution and decrease the solubility of a gaseous solute.

Concentration of Aqueous Solutions

The concentration of an aqueous solution describes the amount of solute present in a given volume of the solvent (water). Common units of concentration include molarity (moles of solute per liter of solution), molality (moles of solute per kilogram of solvent), and mass percent (mass of solute per mass of the solution).

Key concepts

Solvent and Solute

When you mix salt into water to make a salty solution, you're bringing together two important components: the solvent and the solute. The solvent is like a host at a party, where water is usually the one throwing the shindig in an aqueous solution. It's welcoming and ready to bring others into the mix. The solute, like salt, is the guest, dissolving into the host to create a new, uniform substance.

Key Roles in Solutions

Think of solvents as the space where solutes can mingle and interact. In the realm of chemistry, this host-guest relationship is crucial for reactions to take place and for substances to be transported within biological systems. Without a good solvent, a solute is just a passive bystander, but once dissolved, it turns into an active participant in whatever process is going on.

Polarity and Solubility

Polarity is like the personality of a molecule and is directly linked to solubility. It's the trait that dictates who will get along well in the solution mixer. Water's polar personality makes it a social butterfly, able to dissolve many different kinds of solutes. Polar molecules have regions with slight electrical charges, allowing them to form attractions, just like magnets.

'Like Dissolves Like'

This catchy phrase sums up the social scene: polar solutes, which also have that magnetic charm, can easily mix into polar water. Nonpolar solutes, lacking this charm, often find it hard to blend into the water crowd because they don’t share the same electric vibe. This is why oil (nonpolar) and water (polar) don't mix; they're like people with opposite personalities at a party, sticking to their corners.

Factors Affecting Solubility

Solubility, the measure of how much solute can dissolve in a solvent, isn't just about who gets along with who. It's also about the conditions of the party – the temperature and pressure all play a part.

Temperature's Role

Just like how some people are more likely to dance when it's warm, solid solutes typically dissolve better in warm water. On the flip side, gassy solutes are party poopers in the heat, preferring the chill vibes of a cooler setting where they’re more soluble.

Pressure and Presence of Others

For gases, increased pressure is like a loud music beat, encouraging them to dissolve faster. Meanwhile, if the party's already packed with different solutes, newcomers might find it hard to find a space, affecting the solubility of additional solute.

Concentration of Solutions

Concentration is all about the headcount at the solvent-solute party. It measures just how much solute is thrown into the mix in relation to the amount of water. Keeping track of how crowded the party is can be done in different ways.

Counting Guests

Chemists do a roll-call by measuring the molarity, which is like a list of all the moles of solute guests per liter of the solution. Molality is similar, but it pays attention to how many moles are hanging out with a kilogram of our friendly host, water.

Percentage of the Party

And sometimes, it’s all about the size and not the number, where mass percent comes into play – calculating the weight of the solute guests compared to the total weight of the party. Understanding these numbers doesn't just help with homework—it's crucial for chemists to predict how the substances will act and react.