The analysis of lead (Pb) in a sample of solder was carried out using atomic absorption spectroscopy as follows.

1.013 g of solder was completely dissolved in a small volume of nitric acid and the solution made up to 1.000 L with distilled water. A 50.0 μL aliquot of this was then diluted to 100.0 mL with distilled water, and when analysed by atomic absorption in an air/acetylene flame it gave an absorbance of 0.215 at 283.3 nm. The instrument was calibrated, after zeroing with distilled water, with standard solutions of lead containing 0.100 and 0.300 ppm Pb which gave absorbances of 0.120 and 0.360 respectively.
Calculate the wt % of Pb in the solder.

To calculate the weight percentage of Pb in the solder, we need to follow these steps:

Step 1: Calculate the concentration of the diluted solder solution:
To do this, we need to use Beer's Law, which states that the absorbance (A) is directly proportional to the concentration (C) of the absorbing species in the solution.

From the given information, the diluted solder solution has an absorbance of 0.215.

Using the calibration standards, we can determine the concentration of Pb in the diluted solder solution.

At an absorbance of 0.120, the standard solution has a concentration of 0.100 ppm (parts per million).
At an absorbance of 0.360, the standard solution has a concentration of 0.300 ppm.

We can use a linear interpolation to calculate the concentration of Pb in the diluted solder solution.

Absorbance of diluted solder solution = 0.215
Concentration of diluted solder solution = (0.215 - 0.120) / (0.360 - 0.120) * (0.300 - 0.100) + 0.100 = 0.203 ppm (parts per million)

Step 2: Calculate the number of moles of Pb in the diluted solder solution:
To do this, we need to convert the concentration from ppm to mol/L by using the molecular weight of Pb (207.2 g/mol).

Concentration of Pb in the diluted solder solution = 0.203 ppm = 0.000203 g/L = 0.000203 g/1000 mL

Moles of Pb in the diluted solder solution = (0.000203 g/1000 mL) * (1 L / 1000 mL) * (1 mol / 207.2 g) * 1000 mL = 0.000000980 mol

Step 3: Calculate the weight of Pb in the diluted solder solution:
To do this, we multiply the moles of Pb by the molar mass of Pb (207.2 g/mol).

Weight of Pb in the diluted solder solution = 0.000000980 mol * 207.2 g/mol = 0.000203 g

Step 4: Calculate the weight percentage of Pb in the solder:
Now, we need to take into account the dilution factor.

The diluted solder solution was obtained by diluting a 50 μL aliquot to 100.0 mL. Thus, the dilution factor is 100.0 mL / 50 μL x 1000 µL/mL = 2000.

Weight of Pb in the solder = Weight of Pb in the diluted solder solution * Dilution factor
Weight of Pb in the solder = 0.000203 g * 2000 = 0.406 g

Weight percentage of Pb in the solder = (Weight of Pb in the solder / Weight of the solder) * 100
Weight percentage of Pb in the solder = (0.406 g / 1.013 g) * 100 = 40.11%

Therefore, the weight percentage of Pb in the solder is approximately 40.11%.