1. H

    Internal standard calculations..

    I would like to confirm the volume of internal standard (theophylline) and 5 standard solutions (caffeine) I have calculated to analyze caffeine levels in unknown samples... Final total volume = 10ml Stock concentration(caffeine) = 0.4% ; Stock concentration (thophylline) = 0.4% Standard...
  2. JayneDoe

    Standard Sample Size

    Sometimes, when repeated assays are to be performed, the sample size is standardized and chosen such that the ultimately measured quantity is numerically equivalent to some other desired proportionate quantity. Suppose the sulfur content of a mineral sample is determined by complete conversion...
  3. O

    preparation of standard EDTA

    How can I prepare 0.01m of EDTA solution from EDTA powder?
  4. H

    Calculate the volumes of solution III required to make up the standard solutions?

    I.60 mL of Fe(NO3)3 (0.20 M in 0.50M HNO3) for standard solutions II. 70 mL of Fe(NO3)3 (2.0 x 10^-3 M in 0.50 M HNO3) for unknown solutions III. 60 mL of KSCN (2.0 x 10^-3 M in 0.50 M HNO3) for both standard and unknown solutions IV. 100 mL of HNO3 (0.50 M) as solvent Find the volume of...
  5. S

    standard cell potential

    I am using NiSO4 aqueous solution, Pt anode, Cu cathode coated with Au for Ni electroplating (at 3 V DC) on Au. Cu is not exposed to solution. To calculate cell potential should I consider Cu/Pt or Au/Pt. If I replace Pt with graphite, whether for same 3 V DC supply Ni plating would be...
  6. N

    Standard hydrogen electrode

    Is hydrogen used as standard because its best to accept electrons ?
  7. S

    Calculating Standard Enthalpy Change

    Hello! :) I have honestly no idea on how to approach this seemingly easy question, can somebody please provide me with some assistance? I'm adding the enthalpy values up and then entering that as the answer (along with numerous other attempts that have been unsuccessful) and I just don't know...
  8. R

    Looking for a disinfectant testing standard!

    Hello, I am a Chemical Engineering student. Currently, I'm involved in a research meant to determine the potential of Eucalyptus and Rosemary essential oils to be used as disinfectants. We pretend to compare their antibacterial capacity against common quaternary ammonium based products...
  9. R

    Please help - How to calculate the dilution factor for the standard and sample prepar

    Standard : 10 mg of std. sample dissolved in 100 ml MeOH, 2 ml from this 100 ml is diluted to 50 ml MeOH. Sample : To 100 gm of the sample add 50 ml dimethyl sulphoxide, shake & keep at 40'C for 20 mins. Cool & add 50 ml of 50% MeOH. Add 100 ml n-hexane and pass through anhydrous sodium...
  10. D

    Standard Heat of Formation Problem

    Can someone please explain to me how to do this problem: In winemaking, the sugars and grapes undergo fermentation by yeast to yield CH3CH2OH and CO2. During cellular respiration, sugar and ethanol are burned to water vapor and CO2. a. Using C6H12O6 for sugar, calculate deltaH(reaction)...
  11. S

    Standard enthalpy question

    The choice highlighted and the fourth choice is wrong. I know the formula is 2CO+ O2===> 2CO2. Is choice 5 correct? I dont think so since they both have two as a coefficient that the answer would be choice 2 since the formula is products - reactants and itt would be CO2- CO not CO - CO2...
  12. H

    Finding mass of glucose in standard solutions

    his is for an experiment that separates sugars in a sample using TLC. We are given a glucose standard solution with a concentration of 1mg/ml as well as 3 standard sugar solutions (glucose, fructose and maltose) all with the same concentration (10mg/ml) in 10% v/v isopropanol) We are asked to...
  13. S

    Standard enthalpy

    I am given: 2Fe+(3/2)->Fe2O3 ΔHf° =-824 kJ mol^-1 and also: 2FeO+(1/2)O2->Fe2O3 ΔH°=-280 kJ per mol I have to find the standard enthalpy of formation ΔHf° of FeO Can someone show me how to do this? I keep getting -544, but that was marked wrong.
  14. S

    Chemistry, Standard deviation questions, HELP!!!

    In the standard deviation, the decimal place of the first non-zero digit indicates where the precision of the average ends (decimal place where the individual results deviate from each other). All your mass readings have 5-6 significant figures, so one might expect a standard deviation of...