41. Using the following table of prominent absorption wavelengths and molar abso

Question

41. Using the following table of prominent absorption wavelengths and molar absorptivities for napthalene and Molar Absorption Compound wavelength, nmabsorptivity 221 286 312 375 130000 9300 290 0 napthalene 221 312 375 15000 1200 9000 anthracene anthracene, suggest a wavelength at which anthracene can in the presence of an unknown amount of napthalene and calculate the minimum detectable concentration (MDC) of anthracene (in M) at its optimum wavelength. Assume a cell path length of 1.00 cm and the MDC yields a %T of 97.0. Molar Mass anthracene 166 g.mol- (A) 221 nm, 6.7 × 10-6 (C) 375 nm, 1.8 × 10-4 (B) 286 nm, 1.4 x 10-6 (D) 375 nm, 1.5 × 10-6

Explanation / Answer

Napthalene and anthracene both absorb at 221 nm. So in presence of napthalene, anthracene can't be determined at 221 nm. Next strong absorption for anthracene is at 375 nm. So suggestable wavelength to detect anthracene in presence of napthalene is 375nm.

MDC = A/ (Molar absorptivity) *l

= [2- (log(%T)) ]/ [ 9000*1 cm]

= 1.5*10^-6 M

Hence the answer is D) 375, 1.5*10^-6  

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