1. C

    Preparation of Ca/PO4/acetate solution.

    Hi, We need to perform an exploratory study on teeth demineralization. For this purpose, few publications have quoted the use of Ca/PO4/acetate solution containing 2mmol/L calcium, 2 mmol/L phosphate and 0.075 mol/L acetate at pH 4.5. Can anybody help us with the method to prepare such a...
  2. M

    Ammonia/oxygen reaction stoichiometry

    2NH4 +3O2 >> 2NO2 +4H +2H2O - 3.43g O2/g to convert 2NO2 + O2 >> 2NO3 - 1.14g O2/g NO2 oxidized Total oxidation reaction: NH4 + 2O2 >> NO3 +2H -H2O - 4.57g O2/g N oxidized Can someone please explain how the gram of O2 per gram of ammonia/nitrite is calculated? Thanks!
  3. C

    Stoichiometry Problem

    f you reacted 1 mol of aluminum (Al) with 1 mol of iodine gas (I2), what amount of product could be formed? (aluminum’s atomic mass is 26.98 u and the atomic mass for a single iodine atom is 126.90 u). SHOW YOUR CALCULATIONS FOR FULL MARKS (3 points) 2 Al + 3 I2 → 2 Al(I)3 Can someone...
  4. S


    What is STP?
  5. B

    Homework help - gas laws and stoichiometry!

    A candle is burnt inside a sealed container of oxygen gas with a volume of 1500 cm3 at 25oC. Once the reaction is complete and the container has cooled to 25.0oC, what will the pressure be inside the container? Assume the candle has no volume, that all the oxygen is consumed, that candle wax has...
  6. X

    Green Chemistry (Gas Stoichiometry)

    For my chemistry lab, I reacted Mg powder with HCl to create H2 gas. I measured the volume of H2 gas created by salt water displacement by reading off an inverted test tube. I measured 14.0 mL and calculated the percent yield (used PV=nRT to find theoretical volume and divided it by the actual-...
  7. M

    stoichiometry hydroxylamine hydrochloride

    hi forum members, i would really appreciate your assistance with a calculation of the pH adjustment for hydroxylamine hydrochloride: i want to make a 2M solution of HA-HCl in PBS pH7.4 (phosphate-buffered saline) and want to know how much NaOH i have to add to get a solution with pH 8.5 can...
  8. K

    Difficult Stoichiometry Questions?

    Hello, The title really says it all. I was just wondering if anyone could help me by sharing any difficult stoichiometry questions which you may know of. These questions can range from Redox, Solution, Equilibrium constant reactions, Gas-Law problems, Classical-Stoichiometry, Limiting-reagent...
  9. S


    I just started a new chapter on stoichiometry and I'm having some trouble understanding how to proceed on different exercises! Limestone is mostly calcium carbonate, CaCO3, but also contains other minerals. When heated, the CaCO3 decomposes into CaO and CO2. A 1.605g sample of limestone was...
  10. S

    Gas Stoichiometry Question

    Here's the question. A 3.25 gram sample of solid calcium carbide (caC2) reacts with 1.72 mL of water to produce acetylene gas (C2H2) and aqueous calcium hydroxide. If the acetylene was collected at 17.0 degrees C and 740.0 mm Hg, how many milliliters of acetylene were produced? I started off by...
  11. J

    Geochemistry Question

    Hi, I have this problem: Consider a sealed box containing seawater purged with argon gas so that there is no N2 or O2 present. You inject NO3- (to make the initial concentration 100 μmol/L) and CH2O (carbohydrate, to make an initial concentration of 100 μmol/L) into the box. Denitrification...
  12. J


    Hi all. I have this balanced equation: 2FeO3 +6C+ 3O2 => 4Fe +6CO2 The question is "if this process is run until 3940g of Fe is produced, how many grams of CO2 will be produced? This is from my study guide for an upcoming exam, I know the answer is 4644g I just don't know the proper way to...
  13. M

    stoichiometry calculation in organic chemistry

    Hello I need help on caculating this problem that I got stuck on, and couldn't find the exact answer for this, can someone help me solve this? Thank you. Propane will react with molecular bromine to make 2,2-dibromopropane and hydrogen bromide. In this reaction, 6.21 grams of propane react with...
  14. D

    AP Chem/Pre-AP Chem review: Can someone help me with this sol. stoich. question?

    ** We haven't gotten to that part where we take into account that not everything will react completely and we don't subtract the precipitate from the total mL. My class will start taking those things into account after we finish the pre-ap chem review.** Problem: An unknown volume, X of 0.731M...
  15. T

    Can you please check these? (Stoichiometry problems)

    So i'm generally good with Molarity problems but on a few they threw mg/ml into the mix and its throwing me off. I think i did these right but could someone check them? The first problem is, you weigh out exactly 0.250g of CaCo3 (form. weight= 100.09g/mol) and disolve it in exaclty 250 ml of...
  16. D

    stoichiometry problem

    Metal hydroxides react with water to form hydrogen gas and the metal hydroxide. For example, SrH2 (s) + 2H2O (l) --> Sr(OH)2 (s) + 2H2 (g) (Can't figure out how to do subscripts) You wish to calculate the mass of hydrogen gas that can be prepared from 5.70 g of SrH2 and 4.75 g of H2O. a. How...
  17. A

    Stoichiometry Lab Prep

    We are doing a lab in class where we are given 1.24g of iron and need to figure out if it's Fe(III) or Fe(III). We are also given copper(II) sulfate (pentahydrous). The procedure is clear, but we have to figure out what stoich work needs to be done before we start and do the work. My teacher...
  18. E

    Stoichiometry help needed asap!

    52.8kg of sand is reacted w/ 25.8kg of C to produce 22.4kg of pure silicon. Determine the limiting reactant,theoretical yield, and percent yield for this process. I'm not necessarily asking for the answer here, just help as far as setting up the reaction map , it'll be greatly appreciated...
  19. B

    Stoichiometry question

    Homework Question: An experiment often used in highschool chemistry, students react solid copper wire with a solution of silver nitrate to produce pure silver and copper (II) nitrate. Calculate the mass in grams of each product if 3.5 g of copper wire is placed in the solution. How many grams of...
  20. B

    Manufacture of phosphoric acid

    Phosphoric acid is made by reacting the rock phosphate with Hcl. The components of phosphate rock is: Components weight% P2O5 34.55 CaO 48.67 Al2O3+Fe2O3 3.76 MgO 1.29 SiO2 5.58 CaF2 2.50...