A student prepares five aqueous CuSO4 standard solutions by dilution from a 0.500 M stock and measures their absorbance at 635 nm in a 1.00 cm cuvette. The blank is distilled water. Concentrations and absorbances are: 0.050 M (A=0.105), 0.100 M (A=0.210), 0.200 M (A=0.420), 0.300 M (A=0.630), 0.400 M (A=0.840). An unknown CuSO4 solution gives A=0.525 in the same cuvette.
What is the concentration of the unknown CuSO4 solution?
- A
0.105 M
- B
1.10 M
- C
0.525 M
- Dcheck_circle
0.250 M
Explanation
The slope is 2.10 M^-1 (e.g., 0.840/0.400). Using A = slope * c, c = 0.525 / 2.10 = 0.250 M.