Question

Suppose you are given the volume (in liters) of a salt (NaCl) solution and its molarity. Explain how you would determine the moles of salt in this solution.

Short answer

Multiply the molarity by the volume to find moles of salt.

Step-by-step solution

Understanding Molarity

Molarity (M) is defined as the number of moles of solute per liter of solution. So, if you know the molarity of a solution, it tells you how many moles of the solute are present in one liter of that solution.

Using the Molarity Formula

The formula for molarity is: \[ M = \frac{n}{V} \]where \( M \) is the molarity, \( n \) is the number of moles of the solute, and \( V \) is the volume of the solution in liters.

Rearranging the Molarity Formula

To find the number of moles \( n \), rearrange the equation to solve for \( n \):\[ n = M \times V \]Here, \( n \) will be in moles, \( M \) is the molarity in moles per liter, and \( V \) is the volume in liters.

Applying the Formula

Plug in the values you have for molarity (M) and volume (V) into the formula:\[ n = M \times V \]Multiply the given molarity by the volume in liters to find the moles of salt.

Key concepts

Moles of Solute

Determining the moles of a solute in a solution is a fundamental task in chemistry. The moles of solute indicate how much of a specific substance is present within a solution. The concept of moles provides a bridge between the molecular scale and the macroscopic scale in chemistry. It allows chemists to count molecules or atoms by weighing them. To calculate the moles of a solute, you need to use the concept of molarity. Molarity, denoted as \( M \), is defined as moles of solute per liter of solution. If you have the molarity of a solution and its volume, you can easily find the number of moles present using the formula \( n = M \times V \), where:

• \( n \) is the moles of solute
• \( M \) is the molarity in moles per liter
• \( V \) is the volume in liters

Imagine you have a bottle of salt solution: knowing how salty it is and how much solution you have lets you know precisely how much salt (measured in moles) is there. This is vital in reactions that require precise amounts of a substance. Through this formula, chemists can scale their recipes for chemical reactions, whether they are working on a tiny lab bench or a sprawling industrial plant.

Volume of Solution

Understanding the volume of a solution is crucial when working with chemical solutions. The volume typically measured in liters is a critical component of calculating molarity. When dealing with solutions, the volume tells you how much liquid is present in your container. By knowing the volume, especially in conjunction with molarity, you gain insights into how much solute is dispersed in that solution. The typical units for expressing volume in chemistry are:

• Liters (L)
• Milliliters (mL)

Volume measurements often start from mililiters, but in chemical calculations involving molarity, it's important to convert milliliters into liters, because molarity is expressed in moles per liter. This conversion is crucial:

• 1 Liter (L) = 1000 Milliliters (mL)

Example: If you have 250 mL of solution, you would convert it to 0.25 L for molarity calculations. By understanding and correctly measuring volume, you ensure accuracy in your chemical experiments and in the preparation of solutions with specific concentrations.

Chemical Solutions

Chemical solutions are mixtures of two or more substances where one is dissolved in the other. They are a cornerstone of many scientific and engineering processes. In a typical solution, there are two main parts:

• The solute: the substance being dissolved, like sugar in water.
• The solvent: the substance doing the dissolving, typically a liquid like water.

Solutions can be described by their concentration, which tells you how much solute is present in a certain volume of solvent. Molarity is one way to express concentration; it states the number of moles of solute per liter of solution. Understanding chemical solutions involves recognizing how solvents dissolve solutes and how factors such as temperature and pressure can influence the dissolving process. For instance, a hot solution often dissolves more solute than a cold one because increased temperature generally allows the solvent to hold more dissolved particles, thus potentially increasing molarity without changing the solvent volume. Chemical solutions have diverse applications ranging from household cleaning agents to complex industrial processes. Accurately preparing these solutions involves precise measurements and understanding the interactions between solutes and solvents.