signment Attempts Score 2/1/2017 06:00 AM 17.7/20 G 1/24/2017 08:16 PM Gradebook

Question

signment Attempts Score 2/1/2017 06:00 AM 17.7/20 G 1/24/2017 08:16 PM Gradebook Print calculator Periodic Table 100 Sapling Learning Oxybenzone is used in sunscreen because it offers protection in the UVA and UVB regions. Use Beers Law and data provided in the table to determine how many milligrams of oxybenzone are present in 2.5 mL sunscreen. Molar mass of oxybenzone 228.2 g/mol Absorbance Wavelength Molar Extinction Pathength of UV cell Volume of Sample Coefficient Sunscreen 10 14365 M cm 1 1.0 cm 2.5 mL Incorrect. Use the Beer Lambert equation to are calculate the concentration of oxybenzone. resent in 2.5 mL of sunscreen? 0.04 mg Concentration can then be converted to mass. moles concentration x liters The answer contains mass as moles x molar mass two significant figures. A Previous Try Again Next Exit

Explanation / Answer

Beer lambert's law can be defined as

A = abc

where

A = absorbance
a = molar absorptivity,
b = pathlength, and c = molar concentration

here given,

A= .85
a = 14365 M-1cm-1
b = 1 cm
c = to be found

c = 5.917*10-5 M or 5.917*10-5 mol/L

given 1 mole has mass of 228.2 g ie. 228.2g/mol

to get in mg per ml we have to multiply with molar mass

5.917*10-5 mol/L * 228.2g/mol = 1.35*10-2 g/L = 13.5mg/L = 13.5mg/1000mL

13.5mg in 1000mL

13.5mg/1000 in 1mL

(13.5mg/1000)*2.5mL = .03375mg

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