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. U

    Molar calculations - making CuCl2

    I am making CuCl2 - Cu (s) + 2 HCl (aq) -> CuCl2 + H2 My calculation is this: Molar weight of copper is ~63 g/mol thus I have 10/63= ~ 0.16 mol of copper. Making CuCl2 from it should take 2*0.16 ~ 0.32 mol of acid. 32% solution HCl ~ 10 mol which means 1mol ~ 100ml so I need 0.32*100ml ~...
  3. T

    Calculations involving moles and percentage yield

    Hello all! I'm just starting out on chemistry and I don't even know where I would begin with these questions: What volume of a 2.40 mol/L magnesium bromide solution would contain 3.40 x 10^23 atoms of bromine? The reaction of 2.0g of Br2 with 4.0g of F2 produced BeF5 in 45% yield. How many...
  4. S

    Equilibrium calculations

    Hi! Need help with this: In order to study the following reaction: NO+NO2+H2O ==> 2HNO2 a mixture of NO, NO2 and H2O was prepared in a 10.0 L glass bulb at 20*C with the following initial concentrations: [NO]=[NO2] = 2.9*10^-3 M [H2O] = 9.44*10^-4 M [HNO2] = 0.0 M When equilibrium was...
  5. E

    Mole calculations confusion (please help!)

    Hello guys! Im really confused with this one part of calculating the number of moles in 1.00 gram the last part in bold is confusing me. why is the 2 negative? can someone please explain finding a number of moles in a certain number of grams? im really confused : ( this is what the teacher...
  6. F

    More Grav. Analysis & Mole Calculations

    Q1: Kyotorphin (mole mass = 337.4 g/mol) is a small molecule, which has a role in pain regulation. A sample of cerebrospinal fluid taken from a patient has a kyrotorphin concentration of 280 ng/L. Find the number of kyrotorphin molecules in one millilitre of cerebrospinal fluid. n = CV = (2.8 x...
  7. F

    Gravimetric Analysis and Mole Calculations

    Q1: The amount of nickel in a sample of steel was determined by the following method. 3.18 g of the steel was dissolved in a mixture of hydrochloric and nitric acids. This converted all of the nickel into Ni{2+} ions. The solution was neutralised with dilute ammonia and a solution of...
  8. H

    Pharmacy calculations, thermodynamics and tonicity

    Hey guys any help with answering these questions and maybe some explanation would be greatly appreciated: 1. A first order reaction has a half-life of 1.98 days. The rate constant for the reaction is (a) 1.37 days-1 (b) 1972.80 minutes-1 (c) 0.35 days-1 (d) 0.35 mol days 2. The enzyme-catalysed...
  9. S

    Acid-Base and Buffer Calculations

    Hello :) I honestly have NO idea on how to go about this calculation, it appears simple but I'm struggling, can somebody kindly go through the steps with me as I REALLY want to learn this!! What is the Ratio of [Base]/[Acid] in the following Buffer system? Information: Target pH = 9.89 AB...
  10. S

    pH Buffer Calculations

    Hello :o Can somebody PLEASE provide me with a sense on how I answer these two questions? My maths skill is not the best and I although it provides me with an equation I don't know how to use it? :confused: Q1) Refer to the attached image. The acid is Acetic Acid (CH3COOH) and the Conjugate...
  11. S

    Mass-Mass Calculations Practice Help???

    1. 2 N2H4 + N2O4 -----> 3 N2 + 4 H2O If 47.82 g of N2H4 is reacted with 200. g of N2O4, how many g of N2 form? 2. 4 HCl + MnO2 ==> MnCl2 + 2 H2O + Cl2 How many grams of MnCl2 are formed when 36.0 grams of water are also formed? 3.Ca + O2 ==> CaO How many grams of oxygen gas are required to...
  12. W

    Please review my calculations for my titration lab and correct me where I'm wrong.

    DON'T BOTHER GUISE, I HAVE FOUND MY MISTAKES. HOW THE HECK DO I DELETE THIS ALTOGETHER? Aim: To determine the amount of Fe2+ in a dissolved wire solution. Method: 25cm^3 of a sol. Of iron wire in dilute sulphuric acid(some in the form of Fe3+ and some in the form of Fe2+) was pipetted and...
  13. C

    Electromagnetic Radiation Calculations

    Hey everyone, I am having trouble with electromagnetic radiation calculations, and am looking for some help. I know how to do the basic which would be something like: Given a wave with v=6.0x10^14Hz. Find the wavelength of the wave. Now, I need help with a two step problem. So something along...
  14. L


    need help to calculate the # of oxygen molecules in 38.1 g O2
  15. S

    Buffer solutions calculations

    This the question: Q) You need 100 ml of 200 mM phosphate buffer and you have two stock solutions from which you can make the buffer; 0.8 M NaH2PO4 (the acid form) and 0.8 M Na2HPO4 (the base form). You need to add 3 times more of the acid form than the base form to achieve the desired pH. How...
  16. Y

    chemistry calculations

    I don't understand the electrical current part and how it can effect the number of moles, we haven't done anything about it in class.
  17. Y

    chemistry calculations

    A solution was prepared by mixing dilute sulfuric acid and dilute tartaric acid(HOOCCHOHCHOHCOOH). In acid-base reactions releases two prptpms amd forms the tartrate ion : OOCCHOHCHOHCOO(2-)(AQ) The mixture of the two acids was analysed as follows: (i) 25.00 mL of the mixture was taken, and...