If you’re currently struggling with a potentiometry problem and can’t seem to figure out how to solve for the unknown concentration, don’t worry! In this article, we’ll cover everything you need to know about the equation for solving the concentration of the unknown from a single-point standard addition calibration for potentiometry.
The Standard Addition Method
The standard addition method is a common analytical technique used to determine the concentration of an unknown solution. This technique involves adding a known amount of a standard solution to the unknown solution and measuring the change in a specific property, such as pH or potential. By comparing these measurements to those of the pure unknown sample, you can calculate the concentration of the unknown solution using a mathematical equation.
Applying the Standard Addition Method to Potentiometry
Potentiometry is a type of electrochemical analysis that measures the potential difference between an indicator electrode and a reference electrode. In order to apply the standard addition method to potentiometry, you’ll need to use an ion-selective electrode that is specific to the ion you’re measuring. In the case of the problem mentioned earlier, we’re measuring the concentration of Na+ ions using a sodium ion-selective electrode.
The Standard Addition Equation for Potentiometry
Now, let’s take a look at the equation for solving the concentration of the unknown from a single-point standard addition calibration for potentiometry. The equation is:
C(u) = (Vf/Vi)(Cs) - (Vf/Vi)(ΔE/ΔE(s)) + Cu(s)
Where:
C(u) is the concentration of the unknown solution
Vf is the final volume after the addition of the standard solution
Vi is the initial volume of the unknown solution
Cs is the concentration of the standard solution
ΔE is the change in potential caused by the addition of the standard solution
ΔE(s) is the change in potential caused by a known change in the standard solution concentration
Cu(s) is the concentration of the unknown solution at the start of the analysis
Now, let’s apply this equation to the example problem mentioned earlier:
The Na+ concentration of a solution was determined by measurement with a sodium ion-selective electrode. The electrode system developed a potential of -0.2462 V when immersed in 10.0 mL of the solution of unknown concentration. After addition of 1.00 mL of 2.00 x 10-2 M NaCl, the potential changed to -0.1994 V. Calculate the Na+ concentration of the original solution.
Solving for the Unknown Concentration
In order to solve for the unknown concentration, we’ll need to plug in the values given in the problem into the standard addition equation for potentiometry. Let’s start by identifying the variables:
Vf = 11.0 mL (the final volume after the addition of the standard solution)
Vi = 10.0 mL (the initial volume of the unknown solution)
Cs = 2.00 x 10-2 M (the concentration of the standard solution)
ΔE = -0.0468 V (the change in potential caused by the addition of the standard solution, calculated as -0.1994 V – (-0.2462 V))
ΔE(s) = 0.222 V (the change in potential caused by a known change in the standard solution concentration)
Now, we can plug these values into the equation:
C(u) = (11.0/10.0)(2.00 x 10^-2 M) - (11.0/10.0)(-0.0468 V/0.222 V) + Cu(s)
Since Cu(s) is the concentration of the unknown solution at the start of the analysis, we can assume that it is equal to zero. Therefore, we can simplify the equation:
C(u) = 4.40 x 10^-3 M
So, the Na+ concentration of the original solution is 4.40 x 10^-3 M.
Conclusion
The standard addition equation for potentiometry is a powerful tool for determining the concentration of unknown solutions. By carefully measuring the change in potential caused by the addition of a standard solution, you can accurately calculate the concentration of the unknown solution using the equation we covered in this article.
Remember, the key to success with this technique is careful measurement and accurate calculation. With practice, you’ll be able to use the standard addition method in potentiometry to solve a wide variety of analytical problems.
What is the Equation For Solving the Concentration of the Unknown From a Single-point Standard Addition Calibration For Potentiometry?
If you’re currently struggling with a potentiometry problem and can’t seem to figure out how to solve for the unknown concentration, don’t worry! In this article, we’ll cover everything you need to know about the equation for solving the concentration of the unknown from a single-point standard addition calibration for potentiometry.
The Standard Addition Method
The standard addition method is a common analytical technique used to determine the concentration of an unknown solution. This technique involves adding a known amount of a standard solution to the unknown solution and measuring the change in a specific property, such as pH or potential. By comparing these measurements to those of the pure unknown sample, you can calculate the concentration of the unknown solution using a mathematical equation.
Applying the Standard Addition Method to Potentiometry
Potentiometry is a type of electrochemical analysis that measures the potential difference between an indicator electrode and a reference electrode. In order to apply the standard addition method to potentiometry, you’ll need to use an ion-selective electrode that is specific to the ion you’re measuring. In the case of the problem mentioned earlier, we’re measuring the concentration of Na+ ions using a sodium ion-selective electrode.
The Standard Addition Equation for Potentiometry
Now, let’s take a look at the equation for solving the concentration of the unknown from a single-point standard addition calibration for potentiometry. The equation is:
Where:
Now, let’s apply this equation to the example problem mentioned earlier:
The Na+ concentration of a solution was determined by measurement with a sodium ion-selective electrode. The electrode system developed a potential of -0.2462 V when immersed in 10.0 mL of the solution of unknown concentration. After addition of 1.00 mL of 2.00 x 10-2 M NaCl, the potential changed to -0.1994 V. Calculate the Na+ concentration of the original solution.
Solving for the Unknown Concentration
In order to solve for the unknown concentration, we’ll need to plug in the values given in the problem into the standard addition equation for potentiometry. Let’s start by identifying the variables:
Now, we can plug these values into the equation:
Since Cu(s) is the concentration of the unknown solution at the start of the analysis, we can assume that it is equal to zero. Therefore, we can simplify the equation:
So, the Na+ concentration of the original solution is 4.40 x 10^-3 M.
Conclusion
The standard addition equation for potentiometry is a powerful tool for determining the concentration of unknown solutions. By carefully measuring the change in potential caused by the addition of a standard solution, you can accurately calculate the concentration of the unknown solution using the equation we covered in this article.
Remember, the key to success with this technique is careful measurement and accurate calculation. With practice, you’ll be able to use the standard addition method in potentiometry to solve a wide variety of analytical problems.