Unknown Determination 1. Sample Mass: 0.10g Volume of Soultion 50.0mL Absorbance

Question

Unknown Determination

1. Sample Mass: 0.10g    Volume of Soultion 50.0mL

Absorbance or %T                Concentration of Fe (mg Fe/mL)

Trial 1: 0.77                            _______________

Trial 2: 0.73                            _______________

Trial 3: 0.74                            _______________

Mean: 0.7467                        _______________

2. Concentration of Fe in mg/mL __________ +/- ___________

3. Standard Deviation? (show calculations)

4. Percent Fe in original sample (show calculations) _________ +/-__________

I need the blanks filled in for #1 and calulations done for #2,3,4.

Explanation / Answer

Units of Concentration

Once you have identified the solute and solvent in a solution, you are ready to determine its concentration. Concentration may be expressed several different ways, using percent composition by mass, volume percent, mole fraction, molarity, molality, or normality.

This is the mass of the solute divided by the mass of the solution (mass of solute plus mass of solvent), multiplied by 100.

Example:
Determine the percent composition by mass of a 100 g salt solution which contains 20 g salt.

Solution:
20 g NaCl / 100 g solution x 100 = 20% NaCl solution

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