Chem 1106
Law Enforcement Used to prosecute drunk drivers with BAC’s above legal limit of 0.08% Alcohol problems world wide problem 40 % of accidents are Alcohol related BAC=Blood Alcohol Content The ratio of breath alcohol to blood alcohol is 2100 : 1 % BAC = g Ethanol x 2100mL Breath x 100% 52.5 mL Breath 1mL Blood
What Happens to Alcohol in the Body? Absorbed capillaries, tissues and organs Not Metabolized remains a separate component in blood flow Blood flow to alveoli in the lungs, Ethanol evaporates from the blood into the breath since it is volatile, and is released with CO2 upon exhaling
Alcohol in the brain BBB Can cross the BBB Blood brain barrier: barrier that separates the circulating blood from the brain extracellular fluid (BECF) Alters neuronal membranes, ion channels, enzymes, and receptors.
Ethanol reduces Potassium Dichromate turns it into the chromium ion thus you can observe a decrease the yellow color 2 K 2 Cr 2 O CH 3 CH 2 OH + 8 H 2 SO 4 2 Cr 2 (SO 4 ) K 2 SO CH 3 COOH + 11 H 2 O
Use spectrometer in real world application Today they use Infrared detectors Older method is the color Both still apply Beer’s-lambert Law A = bc %ethanol in an unknown sample
Based on Beers Law Concentration proportional to Absorbance A= bC
yellow range 383nm Dichromate is colored yellow with absorbance in yellow range 383nm Beer Law plot. So make it first Then analyze an unknown sample of ethanol Ethanol can only be given by TA Use the stochiometery of the equation Convert to % ALCOHOL (0.1% = 0.25 mg ethanol /mL )
Dichromate is toxic and Corrosive Green pad to protect the bench Goggles, gloves and lab coats Label as directed and prepare area, before coming for Dichromate solution
Add 4 ml Sodium bisulfate solution and 20 ml water rinse the graduated cylinder with 5 mL water and add to beaker Calibrate the spectrometer Get dichromate, ml for stock beaker No solution will be issued If desk is not ready
First need the stock solution concentration = pre-lab Calculate the concentration using the linear regression curve y=mx+b 3. A= 442[Chromate]
Step 1 [ chromate] from the stock solution to calculate how many moles of dichromate are available to react (___mol Cr 2 O 7 -2 /L )* (0.005L )= ___mol Cr 2 O 7 -2 Step 2 Then use the[ Cr 2 O 7 -2] and the volume of the unknown solution ( mL) to calculate the # of moles of the dichromate ion in the unknown. (__mol Cr 2 O 7 -2 /L) *( __L) = __mol Cr 2 O 7 -2 How many moles of dichromate reacted with the ethanol?
Answer 5a- answer 5b= mol Cr 2 O 7 -2 reacted w/ the ethanol Moles Cr 2 O 7 -2 reacted w/ ethanol = _______mol Cr 2 O 7 -2 Next is about the stochimetery 2 moles of dichromate will consume 3 moles of ethanol. Convert to the %BAC 0.10 %BAC = mg ethanol/ mL of any Correct the manual NOT /mL it is g/mol [Answer from 7b]* [______ C 2 H 5 OH g/mole]* [___mg/g] = ____mg C 2 H 5 OH % ERROR known value –experimental known value calculate how many moles of dichromate there were before and after the reaction with ethanol? 2 K 2 Cr 2 O H 2 SO C 2 H 5 OH 2 Cr 2 (SO 4 ) 3 +2K 2 SO CH 3 COOH +11 H 2 O
Dilutions must be accurate (M1V1=M2V2) Take your time here otherwise you are Doomed Timing is critical for Experiment 2 min. and swirl solution Take only the solution you need because waste is toxic Clean station and turn off microlab
waste stock dilution
1 Microlab beer’s law [Stock sol’n] molar concentration from prelab dilutions concentration (M1V1 = M2V2) 2, 3 and 4 equipment ready waste 10 mL NaHSO 4 1 mL Calibrate (water blank) K 2 Cr 2 O 7 ~12mL stock Read abs 9 stock 10
11 Rinse waste dilution 1 mL H 2 O 12 stock 5 mL K 2 Cr 2 O dilution Read abs dilution 17 1 st Dilution M 1 V 1 = M 2 V 2 M stock V stock = M dil V dil M stock (5mL) = M dil (6mL) Prelab ?
dilut nd Dilution M 1 V 1 = M 2 V 2 M stock V stock = M dil V dil M stock (5mL) = M dil (7mL) dilution 1 mL H 2 O 18 dilution 2 Read abs dilut READ Unknown procedure 1-3 dilution 1 mL UNKNOWN 6-7 stock 5 mL K 2 Cr 2 O Unknown dilution Read abs 8-11