Harr: Clinical Chemistry Questions And Answers With Complete Solutions

Which formula correctly describes the relationship between absorbance and %T ? A. A = 2 - log %T B. A = log 1/T C. A = -log T D. All of these options correct answer: D. All of these options D Absorbance is proportional to the inverse log of transmittance. A = -log T = log 1/T Multiplying the numerator and denominator by 100 gives: A = log (100/100 X T) 100 X T = %T, substituting %T for 100 X T gives: A = log 100/%T A = log 100 - log %T A = 2.0 - log %T For example, if %T = 10.0, then: A = 2.0 - log 10.0 log 10.0 = 1.0 A = 2.0-1.0 = 1.0 A solution that has a transmittance of 1.0 %T would have an absorbance of: A. 1.0 B. 2.0 C. 1% D. 99% correct answer: B. 2.0 B A = 2.0 - log %T A = 2.0 - log 1.0 The log of 1.0 = 0 A = 2.0 In absorption spectrophotometry: A. Absorbance is directly proportional to transmittance B. Percent transmittance is directly proportional to concentration C. Percent transmittance is directly proportional to the light path length D. Absorbance is directly proportional to concentration correct answer: D. Absorbance is directly proportional to concentration D Beer's law states that A = a × b × c, where a is the absorptivity coefficient (a constant), b is the path length, and c is concentration. Absorbance is directly proportional to both b and c. Doubling the path length results in incident light contacting twice the number of molecules in solution. This causes