How can the conductivity of a salt solution be decreased

The conductivity of a salt solution is fundamentally related to the concentration of ions present in the solution. To decrease the conductivity, it is necessary to reduce the number of freely moving ions.

Method to Decrease Conductivity

The most effective way to accomplish this is by diluting the solution. This involves adding more water to the existing solution, which increases the volume and spreads out the ions, thereby reducing their concentration.

Mathematical Explanation

The relationship between conductivity ($\sigma$) and concentration ($c$) can be expressed as:

Where $\lambda$ is the molar conductivity. By adding more water, the concentration $c$ decreases, which in turn lowers the conductivity $\sigma$.

Practical Approach

To achieve this:

1. Measure the initial volume $V_i$ and concentration $c_i$ of the salt solution.
2. Determine the desired final concentration $c_f$.
3. Calculate the final volume $V_f$ required to achieve this concentration: $$V_f = \frac{c_i \times V_i}{c_f}$$
4. Add the difference in volumes $V_{add}$, calculated as: $$V_{add} = V_f - V_i$$ which is the amount of water to be added to decrease the conductivity.

Example Calculation

Suppose we have 1 L of salt solution with an initial concentration of 1 M. To dilute it to a 0.1 M solution:

Adding 9 liters of water will decrease the concentration, thereby reducing the conductivity.

Conclusion

Decreasing the conductivity of a salt solution is effectively achieved by adding more water, which dilutes the solution and reduces the concentration of ions. This straightforward method is supported both practically and mathematically, ensuring a lower conductivity for the solution.

Explanation

Dilution involves reducing the concentration of a solute in a solution, typically by adding more solvent. This process is essential in various scientific and industrial applications.

Concentration and Dilution

When you have a solution, its concentration can be described as the amount of solute per unit volume. During dilution, the amount of solute stays constant, but the volume of the solution increases, leading to a lower concentration.

Important Formulas

The dilution process can be described mathematically. The key formula for dilution is:

Where:

• $C_1$ is the initial concentration
• $V_1$ is the initial volume
• $C_2$ is the final concentration
• $V_2$ is the final volume

Practical Example

Suppose you have a 1 M (molar) solution and you want to dilute it to a 0.5 M solution. If you start with 100 mL of the 1 M solution:

Given:

• $C_1 = 1 \, \text{M}$
• $V_1 = 100 \, \text{mL}$
• $C_2 = 0.5 \, \text{M}$

We need to find $V_2$:

Solving for $V_2$:

Thus, you would need to add sufficient water to bring the total volume to 200 mL. Starting with 100 mL of the original solution, you would add 100 mL of water.

Conclusion

Dilution of solution is a fundamental concept used to achieve desired concentrations in various applications by adding more solvent to a solution, thereby reducing the concentration of the solute. The primary formula $C_1 V_1 = C_2 V_2$ helps ensure accurate and precise calculations.

Explanation

The relationship between conductivity and ion concentration is fundamental in the field of chemistry, particularly in the study of electrolytes and their behavior in solutions. Here, we'll discuss how conductivity is influenced by ion concentration and the principles behind this relationship.

Electrical Conductivity

Electrical conductivity is a measure of a material's ability to conduct an electric current. In solutions, particularly aqueous solutions, this conductivity is due to the movement of ions.

Ion Concentration

Ion concentration refers to the number of ions in a given volume of solution. The more ions present, the higher the likelihood that the solution can conduct electricity because ions act as charge carriers.

Relationship

The conductivity $\kappa$ (kappa) of an ionic solution is directly proportional to the concentration of ions in the solution. This relationship can be described by the following formula:

Where:

• $\kappa$ is the conductivity.
• $\lambda_i$ is the molar conductivity of ion $i$.
• $c_i$ is the concentration of ion $i$.

Molar Conductivity

Molar conductivity ($\Lambda_m$) of an ion is the conductivity of a solution containing 1 mole of the ion per liter and varies with concentration. At infinite dilution, the ions are far apart and do not interact with each other, thus, the molar conductivity reaches a maximum value, $\Lambda_m^\circ$, which is a constant for each ion.

Variability with Concentration

For strong electrolytes, the conductivity increases with concentration up to a point, after which it starts to decrease due to ion pairing and other interactions. For weak electrolytes, the degree of ionization increases with dilution, affecting the conductivity differently.

Important Formulas

The conductivity can be broken down into its contributions from individual ions:

Where:

• $\lambda_+$ and $\lambda_-$ are the molar conductivities of the positive and negative ions, respectively.
• $c_+$ and $c_-$ are the concentrations of the positive and negative ions, respectively.

Conclusion

Understanding this relationship is crucial for applications ranging from industrial processes to biological systems, as it helps in determining the purity and composition of solutions. The higher the ion concentration, typically, the greater the electrical conductivity, as long as the system adheres to ideal behavior.