Question

The absorbance of a \( 5 \times 10^{-4} \, M \) solution of tyrosine at 280 nm wavelength is 0.75. The path length of the cuvette is 1 cm. The molar absorption coefficient at the given wavelength in \( \text{M}^{-1} \text{cm}^{-1} \), correct to the nearest integer, is ______.

Hint:

The molar absorption coefficient can be calculated using Beer-Lambert's law, which relates absorbance, concentration, and path length.

Answer 1

Correct Answer: 1500

The molar absorption coefficient \( \epsilon \) can be calculated using Beer-Lambert's law: \[ A = \epsilon \cdot c \cdot l \] where:
- \( A = 0.75 \) (absorbance),
- \( c = 5 \times 10^{-4} \, M \) (concentration),
- \( l = 1 \, \text{cm} \) (path length).
Rearranging to solve for \( \epsilon \): \[ \epsilon = \frac{A}{c \cdot l} = \frac{0.75}{(5 \times 10^{-4}) \times 1} = 1500 \, \text{M}^{-1} \text{cm}^{-1} \] Thus, the molar absorption coefficient is \( 1500 \, \text{M}^{-1} \text{cm}^{-1} \).