Dilution Calculations: Understanding the Concentration of NaCl in Mixed Solutions
Dilution Calculations: Understanding the Concentration of NaCl in Mixed Solutions
In this article, we will explore a common chemistry problem involving the dilution of sodium chloride (NaCl) in mixed solutions. Specifically, we will calculate the final concentration of NaCl when 5 liters of a 2M NaCl solution is mixed with 2 liters of a 5M HCl solution. Understanding this concept is crucial in chemistry and can be beneficial in a variety of fields, from laboratory experiments to industrial applications.
Key Concepts: Molarity and Volume Addition
Molarity, often denoted by the symbol M, is a unit of concentration. It is defined as the number of moles of solute per liter of solution. Mathematically, this can be expressed as:
[ text{Molarity (M)} frac{text{Moles of solute (mol)}}{text{Volume of solution (L)}} ]
Using this formula, we can solve a wide range of chemistry problems, including dilution calculations. The key is to understand that the volumes of the solutions are additive when they are mixed under ideal laboratory conditions.
Mixing Solutions: A Practical Example
Let's consider the scenario where we have two different solutions of NaCl—one with a concentration of 2M and another with 5M. If we mix these solutions, we need to determine the final concentration of NaCl. The process involves the following steps:
Mixing 5L of 2M NaCl with 2L of 5M HCl
First, we calculate the number of moles of NaCl in the 5L of 2M solution:
[ text{Moles of NaCl} frac{text{Molarity (M)}}{text{Volume (L)}} frac{2 , text{mol/L}}{5 , text{L}} 10 , text{mol} ]
Similarly, we calculate the number of moles of HCl in the 2L of 5M solution (though HCl will not be part of our final NaCl concentration calculation):
[ text{Moles of HCl} frac{5 , text{mol/L}}{2 , text{L}} 10 , text{mol} ]
The volumes of the solutions are additive, so the total volume of the mixture is:
[ text{Total Volume} 5 , text{L} 2 , text{L} 7 , text{L} ]
Calculating the Final Concentration of NaCl
To find the final concentration of NaCl, we use the formula for molarity, but this time the volume of the solution is the total volume of the mixture:
[ text{Final Concentration of NaCl} frac{text{Moles of NaCl}}{text{Total Volume}} frac{10 , text{mol}}{7 , text{L}} approx 1.43 , text{mol/L} ]
Therefore, the final concentration of NaCl in the mixed solution is approximately 1.43 mol/L.
Note: The dilution of HCl serves to distract from the main calculation of NaCl concentration. It is crucial to focus on the appropriate solute and its initial moles when performing these calculations.
Conclusion
Understanding how to perform dilution calculations is an essential skill in chemistry. By applying the principles of molarity and volumes, we can accurately determine the concentrations of solutes in mixed solutions. This knowledge is invaluable in various fields, including pharmaceuticals, chemical engineering, and environmental science. With practice, you will become more adept at solving such problems quickly and efficiently.