Question

Beryllium(II) forms a complex with acetylacetone (166.2 g/mol). Calculate the molar absorptivity of the complex, given that a 2.25 ppm solution has a transmittance of 37.5% when measured in a 1.00-cm cell at 295 nm, the wavelength of maximum absorption

Answer 1

Solution.

$2.25 \ ppm = 2.25 \times 10^{-3} \ g/L$

$Cm = \frac{m}{M \times V}$

$Cm = \frac{2.25 \times 10^{-3}}{166.2} = 1.35 \times 10^{-5} M$

$A = \xi \times l \times Cm$

$\xi = \frac{A}{l \times Cm}$

$A = lg[\frac{I0}{I}]$

$A = lg[\frac{100}{37.5}] = 0.426$

$\xi = \frac{0.426}{1 \times 1.35 \times 10^{-5}} = 3.16 \times 10^4 \ \frac{L}{mol \times cm}$

Answer:

$\xi = 3.16 \times 10^4 \ \frac{L}{mol \times cm}$