# 4.1 Day 3 Prelab

Questions

1. What is the transmittance?

2. What is the Absorbance?

3. Pure hexane has negligible ultraviolet absorbance above a wavelength of 200 nm. A solution prepared by dissolving 25.8 mg of benzene ($$C_6H_6$$, FM 78.11) in hexane and diluting to 250.0 mL had an absorption peak at 256 nm and an absorbance of 0.266 in a 1.000-cm cell. Find the molar absorptivity of benzene at this wavelength.

EXTRA

4. A compound with molecular mass 292.16 g/mol was dissolved in a 5-mL volumetric flask. A 1.00- mL aliquot was withdrawn, placed in a 10 mL volumetric flask, and diluted to the mark. The absorbance

at 340 nm was 0.427 in a 1.000-cm cuvet. The molar absorptivity at 340 nm is $$\epsilon_{340}$$= 6130M (a) Calculate the concentration of the compound in the cuvet.
(b) What was the concentration of compound in the 5-mL flask?
(c) How many milligrams of compound were used to make the 5-mL solution?