A sample of nickel is to be determined using absorption spectrum analysis.

Question

A sample of nickel is to be determined using absorption spectrum analysis. A 0.286 g sample of nickel ore is crushed and digested in 1M HNO3. The stock solution is then diluted to 250.0 mL in a volumetric flask (assuming the solution has a density = 1.00 g/mL).

The analysis then proceeds as follows:

Sample Solution. Std Ni solution (11.2ppm)

15.0ml. 0.00ml

15.0ml. 5.00ml

Final volume. Transmittance

100.0ml. 54.1%

100.0ml. 19.9%

Calculate the percent nickel in the original ore sample

Answer 1

Certainly! Here's a revised version of the text to make it clearer and correct any errors:

To calculate the percent nickel in the original ore sample, follow the steps based on the data provided for absorption spectrum analysis:

1. Calculate the concentration of Ni in the standard solution:

- Standard Ni solution concentration is 11.2 ppm (parts per million).

- 1 ppm is equivalent to 1 mg/L, which is further equal to 1 mg/1000 mL, i.e., 0.001 mg/mL.

- Therefore, 11.2 ppm equals 11.2 × 0.001 mg/mL, resulting in 0.0112 mg/mL.

2. Determine the amount of Ni in the standard solution used:

- From the given data:

- Volume of standard Ni solution used = 5.00 mL.

- Concentration of standard Ni solution = 0.0112 mg/mL.

- Amount of Ni in standard solution = Volume × Concentration, which equals 5.00 mL × 0.0112 mg/mL, resulting in 0.056 mg Ni.

3. Calculate the absorbance of the sample solutions:

- Absorbance (A) is related to transmittance (T) by the formula: \( A = -\log_{10}(T) \).

- Transmittance values provided:

- For a 15.0 mL sample solution, T = 54.1%, so A = -log(0.541) ≈ 0.266.

- For a 15.0 mL sample solution, T = 19.9%, so A = -log(0.199) ≈ 0.700.

4. Prepare a calibration curve:

- Plot absorbance (A) versus the concentration of Ni for the standard solutions.

- Use the absorbance values and concentrations of Ni from the standard solutions to interpolate the concentration of Ni in the sample solutions.

5. Calculate the concentration of Ni in the sample solutions:

- Use the absorbance values of the sample solutions and the calibration curve to find the concentration of Ni in each sample solution.

6. Determine the concentration of Ni in the original ore sample:

- Since the sample was diluted to 250.0 mL after digestion, the concentration of Ni in the sample solution is related to the dilution factor.

- Calculate the mass of Ni in the sample solution and then relate it to the mass of the original ore sample (0.286 g) to find the percent nickel.

It's important to note that without the exact calibration curve and additional absorbance data, the exact percent of nickel cannot be calculated. Typically, the absorbance values of the sample solutions are compared to the calibration curve to determine their nickel concentrations, which are then used to calculate the percent nickel in the original ore sample.