Standard Addition Chemistry problem

In summary, the problem involves finding the initial concentration of lead in a sample using standard addition. The equation used is Cx = bCs/mVx, where Cx is the concentration of the sample, b is the y-intercept, Cs is the concentration of the standard, m is the slope, and Vx is the volume of the sample. The attempt at a solution involved plotting the data on a graph and using the equation y=.209x+2.211, where x represents the added lead in mg/mL and y represents the absorbance. However, the necessary information for the variables in the equation (volume and concentration of standard) were not given in the problem statement, leaving the student unsure of how to proceed.
  • #1
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Homework Statement


hw10.jpg



Homework Equations


Not completely sure, but I believe equation is:
Cx = bCs/mVx
cx = concentration of sample
b= y-intercept
cs= concentration of standard
m=slope
Vx=volume of sample


The Attempt at a Solution


I plotted the values on a graph with Absorbance on the Y-axis and [Pb] added on the X-axis, and put a trendline extending through the X axis. Eqn I came up with is y=.209x+2.211

My teacher was very vague with standard addition and through searching the web it said the best way to figure out the initial concentration is through spiking the samples. I am really not sure where to else to go with this problem since my equation above has several variables that aren't given in the problem statement (volume, concentration of standard).
 
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  • #2
Well? X in this case represents the added lead in mg/mL. What would the value of y represent when x=0?
 

Related to Standard Addition Chemistry problem

1. What is a standard addition chemistry problem?

A standard addition chemistry problem is a method used in analytical chemistry to determine the concentration of an unknown substance in a sample. This is done by adding a known amount of the substance to the sample and measuring the resulting change in concentration. This allows for a more accurate determination of the unknown substance's concentration, especially in complex sample matrices.

2. How does the standard addition method work?

The standard addition method involves adding a known amount of a standard solution to a sample, followed by measuring the resulting change in concentration. This is then used to calculate the concentration of the unknown substance in the sample. The key principle behind this method is that the added standard solution must react with the unknown substance in the sample in the same manner as it would in a pure solution, allowing for accurate determination of the unknown substance's concentration.

3. When is the standard addition method used?

The standard addition method is commonly used in situations where the sample matrix is complex and may interfere with traditional analytical methods. It is also useful when the concentration of the unknown substance is low and difficult to measure accurately. Additionally, this method is often used in the analysis of biological samples, as they tend to have high levels of matrix interference.

4. What are the advantages of using the standard addition method?

The standard addition method has several advantages over traditional analytical methods. Firstly, it eliminates the need for a calibration curve, which can be time-consuming and prone to error. Additionally, it can account for matrix interference, leading to more accurate results. This method also allows for a more accurate determination of low concentrations of an unknown substance.

5. Are there any limitations to the standard addition method?

While the standard addition method has many advantages, it also has some limitations. It can be time-consuming and requires a larger sample size compared to other methods. Additionally, this method may not be suitable for samples with high concentrations of the unknown substance, as it may lead to an excessive increase in concentration and skew the results. It also requires careful preparation and handling of the standard solution to ensure accurate results.

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