Understanding the Molarity of Sodium Chloride Solution

The molarity of a solution is a measure of the concentration of a solute in a solution. Specifically, it is defined as the number of moles of solute dissolved in one liter of solution. In this article, we will go through the steps to calculate the molarity of a 1.5L solution that contains 0.25g of NaCl (sodium chloride).

Step-by-Step Calculation of Molarity

Molarity (M) can be calculated using the formula:

Molarity M moles of solute / liters of solution

Calculate the moles of NaCl:

First, we find the molar mass of NaCl (sodium chloride). The molar mass can be determined as follows:

Molar mass of NaCl Molar mass of Na Molar mass of Cl

Molar mass of Na approximately 22.99 g/mol

Molar mass of Cl approximately 35.45 g/mol

Molar mass of NaCl 22.99 g/mol 35.45 g/mol 58.44 g/mol

Now, we calculate the number of moles of NaCl in 0.25g:

Moles of NaCl mass (g) / molar mass (g/mol) 0.25 g / 58.44 g/mol ≈ 0.00429 mol

Calculate the molarity:

Using the number of moles (0.00429 mol) and the volume of the solution (1.5L), we can find the molarity:

Molarity M moles / liters 0.00429 mol / 1.5 L ≈ 0.00286 M

Thus, the molarity of the solution is approximately 0.00286 M.

Conclusion

The calculation of molarity is a fundamental concept in chemistry, aiding in determining the concentration of solutions. By using the given data and following the steps outlined, we can accurately calculate the molarity of a solution containing sodium chloride.

Additional Considerations

Let's consider a related example: what is the molarity of a 1L solution that contains 0.25g NaCl? Here are the steps:

Molar mass of NaCl 22.900 35.45 58.35 g/mol

Moles of NaCl mass (g) / molar mass (g/mol) 0.25 g / 58.35 g/mol ≈ 0.00428 mol

Molarity M moles / liters 0.00428 mol / 1.00 L 0.00428 M

So, the molarity of this solution is 0.00428 M.

Significant Figures and Precision

When dealing with significant figures, it is important to consider the precision of the measurements. In the previous example, the molarity was calculated as 0.0042778919 M, but for simplicity and to match the precision of the mass measurement (0.25g), we can express it as 0.00428 M.

Chemical vs. Physical Change in Dissolution of NaCl in Water

The dissolution of sodium chloride in water is a physical change. This process involves the interaction between the ions of NaCl and the water molecules, leading to a solution where Na and Cl- ions are surrounded by water molecules. The ions are distributed throughout the solution, and the overall integrity of the NaCl compound is not altered.

For more information on molarity, solutions, and related topics, continue reading below or refer to further resources and tutorials. Happy learning!