Objective: Determine the mass of Copper in a single copper screw via spectroscopy.
Overview: React the brass screw with nitric acid. Nitric acid is very corrosive and will be done in the fume hood.
Cu (s) + H+ (aq) + NO3- (aq) —> Cu2+ (aq) + NO (g) + H2O(l)
Copper (II) is blue. We can then use this property to determine the concentration of Copper ions and thus the mass of copper in a single screw. In order to determine the concentration of a specific blue color we will need to make known copper(II) nitrate solutions. We are starting with a stock solution of Copper (II) nitrate and each group will make a known solution. These known solutions will be tested to determine %T of the correlating concentrations. A Beer's law plot will be made after which we will be able to convert any %T copper(II) nitrate solution to concentration.
Procedure:
- Collect a sample of brass screws.
- In the fume hood add 20 mL of 6M HNO3. Leave it in the fume hood to react.
- Create a known copper (II) nitrate solution. You will be assigned a dilution to make of the stock copper (II) nitrate.
- Test your known for %T.
- Put your value on the board.
- Collect your copper from your brass screws. Dilute your sample to 50ml using distilled water. Then add to a 100mL volumetric flask.
- Fill this flask to exactly 100mL.
- Test your unknown for %T.
- Create a Beer's Law plot with entire classroom data.
- Calculate your concentration of Cu2+.
Determine the mass of copper in a penny.
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