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Unformatted text preview: CH455 Exam 1 Prof. J. A. Holcombe June 10,2009 Name X6Y (Also write your mIme in the upper right hand corner ofthe back side ofthe last page ofthis exam.) 1. You receive the analysis results from the lab on the plant's effluent stream. You are told that the average concentration ofa manufacturing byproduct is 4.40 ppb with a sample standard deviation, s, of 0.3 ppb for their triplicate analysis. You are also infonned by the analyst that the method (which they us~ quite often) has a known precision (a) of±0.2 ppb. 1'\-:::- 3 a) Briefly explain the relationship between s and a and when you might expect them to have the same numerical value. (10 piS) S i, 11011 ~sl,-tttt., .-( er ~6"'1 ~ .f'::".k .... L4~"-'.p~. b) You explain all this to your boss who gets upset and explains, "All I want is the answer with a statement of the uncertainty so 1can feel confident that there's less than a 5% chance that the real value is outside the range of values we report!". What do you report? (Show your work) (10 piS) P;O_!:._O._Z_3_ td c) If you use a standard reference material with a known concentration of 4.5 ppb, what are the chances that a single detennination using this method would give a value greater than 5.0 ppb? (10 piS) ~-= ~- X 1 _ '-- 0 Cl~= 0.5"- O. tff(ft= t .').>c' oj-- 2. You construct a calibration curve for a spectrophotometric technique that fits the linear equation:...
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- Summer '08
- Chemistry, numerical value, Standard Reference Material