Frequently Asked Question

(a) To prepare 500 mL of approximately 0.20 M NaOH using solid NaOH, follow these steps:

1. Calculate the mass of NaOH needed using the formula: mass = moles × molar mass

moles = concentration × volume
moles = 0.20 M × 0.500 L
moles = 0.100 mol

mass = 0.100 mol × 40.00 g/mol
mass = 4.00 g

2. Weigh out 4.00 g of solid NaOH using an analytical balance.

3. Dissolve the NaOH in a small amount of water (e.g., 50 mL) in a beaker.

4. Transfer the solution to a 500-mL volumetric flask and dilute to the mark with water.

5. Mix thoroughly.

(b) To prepare 1 L of 150.0 ppm Cu using Cu metal, follow these steps:

1. Calculate the mass of Cu needed using the formula: mass = concentration × volume × molar mass

concentration = 150.0 ppm = 150.0 mg/L = 0.150 g/L
volume = 1 L
molar mass of Cu = 63.55 g/mol

mass = 0.150 g/L × 1 L × 63.55 g/mol
mass = 9.53 mg

2. Weigh out 9.53 mg of Cu metal using an analytical balance.

3. Dissolve the Cu in a minimum amount of concentrated nitric acid (e.g., 1 mL) in a small beaker.

4. Evaporate the solution to dryness on a hot plate to remove the nitric acid.

5. Dissolve the residue in a small amount of water (e.g., 50 mL) and transfer to a 1-L volumetric flask.

6. Dilute to the mark with water and mix thoroughly.

(c) To prepare 2 L of 4% v/v acetic acid using concentrated glacial acetic acid (99.8% w/w acetic acid), follow these steps:

1. Calculate the volume of glacial acetic acid needed using the formula: volume = (% v/v) × total volume

% v/v = 4%
total volume = 2 L

volume = 4% × 2 L
volume = 80 mL

2. Measure out 80 mL of glacial acetic acid using a graduated cylinder.

3. Transfer the glacial acetic acid to a 2-L volumetric flask.

4. Dilute to the mark with water and mix thoroughly.