Calculate The Molarity of Each of The Following Solutions Chegg

Molarity is a fundamental concept in chemistry that measures the concentration of a solute in a solution. It's expressed as moles of solute per liter of solution (mol/L). This calculator helps you determine the molarity of solutions quickly and accurately.

What is molarity?

Molarity (M) is a measure of the concentration of a solution, defined as the number of moles of solute dissolved in one liter of solution. It's one of the most common ways to express solution concentration in chemistry.

The molarity formula is:

Molarity (M) = Moles of Solute / Volume of Solution (L)

Where:

Moles of Solute - The amount of substance in grams divided by its molar mass
Volume of Solution - The total volume of the solution in liters

Molarity formula

The molarity formula is straightforward but essential for accurate calculations:

M = n / V

Where:

M = Molarity (mol/L)
n = Number of moles of solute (mol)
V = Volume of solution (L)

To calculate the number of moles from mass, you can use the formula:

n = mass / molar mass

How to calculate molarity

Calculating molarity involves these steps:

Determine the mass of the solute in grams
Find the molar mass of the solute (from a periodic table or chemistry reference)
Calculate the number of moles using n = mass / molar mass
Determine the total volume of the solution in liters
Divide the number of moles by the volume to get molarity

Tip: Always ensure your units are consistent. Convert grams to kilograms if needed, and milliliters to liters if working with small volumes.

Example calculations

Let's work through an example calculation:

Example 1: Sodium Chloride Solution

You have 5.85 grams of NaCl dissolved in 100 mL of water. What is the molarity?

Molar mass of NaCl = 58.44 g/mol
Moles of NaCl = 5.85 g / 58.44 g/mol ≈ 0.1001 mol
Volume = 100 mL = 0.100 L
Molarity = 0.1001 mol / 0.100 L ≈ 1.001 M

The molarity is approximately 1.00 M.

Example 2: Sugar Solution

You dissolve 10 grams of sucrose (C₁₂H₂₂O₁₁) in 500 mL of water. What is the molarity?

Molar mass of sucrose = 342.3 g/mol
Moles of sucrose = 10 g / 342.3 g/mol ≈ 0.0292 mol
Volume = 500 mL = 0.500 L
Molarity = 0.0292 mol / 0.500 L ≈ 0.0584 M

The molarity is approximately 0.0584 M.

Common mistakes

When calculating molarity, these common errors can occur:

Incorrect unit conversion - Forgetting to convert milliliters to liters or grams to moles
Using the wrong molar mass - Using the wrong value for the solute's molar mass
Volume measurement errors - Not accounting for the total volume including the solute
Significant figures - Reporting more decimal places than justified by the input data

Remember: Always double-check your units and significant figures in your calculations.

FAQ

What is the difference between molarity and molality?

Molarity measures moles of solute per liter of solution, while molality measures moles of solute per kilogram of solvent. Molarity changes with temperature because volume changes, while molality remains constant.

How do I convert molarity to molality?

You need to know the density of the solution. The formula is: Molality = (Molarity × Density of Solution) / Density of Solvent.

What is the molarity of a 1 M solution?

A 1 M solution contains 1 mole of solute dissolved in 1 liter of solution. This is the standard concentration unit in chemistry.