Stoichiometry Definition and 164 Threads

Stoichiometry is the calculation of reactants and products in chemical reactions in chemistry.
Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products, leading to the insight that the relations among quantities of reactants and products typically form a ratio of positive integers. This means that if the amounts of the separate reactants are known, then the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of the products can be empirically determined, then the amount of the other reactants can also be calculated.
This is illustrated in the image here, where the balanced equation is:

Here, one molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water. This particular chemical equation is an example of complete combustion. Stoichiometry measures these quantitative relationships, and is used to determine the amount of products and reactants that are produced or needed in a given reaction. Describing the quantitative relationships among substances as they participate in chemical reactions is known as reaction stoichiometry. In the example above, reaction stoichiometry measures the relationship between the quantities of methane and oxygen that react to form carbon dioxide and water.
Because of the well known relationship of moles to atomic weights, the ratios that are arrived at by stoichiometry can be used to determine quantities by weight in a reaction described by a balanced equation. This is called composition stoichiometry.
Gas stoichiometry deals with reactions involving gases, where the gases are at a known temperature, pressure, and volume and can be assumed to be ideal gases. For gases, the volume ratio is ideally the same by the ideal gas law, but the mass ratio of a single reaction has to be calculated from the molecular masses of the reactants and products. In practice, due to the existence of isotopes, molar masses are used instead when calculating the mass ratio.

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    How Many Moles of Aluminum Are Needed to Form 3.4 Moles of Aluminum Oxide?

    Aluminum oxide is formed from the reaction of metallic aluminum with oxygen gas. How many moles of Aluminum are needed to form 3.4 moles of Aluminum oxide? I don't necessarily need help solving the problem itself (I want to try to do it on my own) but I don't understand how to set the...
  2. G

    Stoichiometry in dimensional analysis

    Anyone here knows what or even how to do stoichiometry what i need is the set up to do stoichiometry in dimensional analysis. i thank you if you can find any info on this matter i would like to know the steps thanks.
  3. Q

    Organic Chemistry Lab: Calculate NaBH4 Needed to Reduce Acetophenone

    Im taking an organic chemistry lab, must calculate the following: NaBH4 is normally prepared for use in basic aqueous solution. Calculate the mass of a 12% NaBH4 aqueous solution required theoretically to reduce 5.00 g of acetophenone. I am can probably have a go at this question if I can get...
  4. U

    Chemistry - Stoichiometry - Some limiting reactants

    Did I answer these questions correctly? 5. In the reaction N2 + 3H2 -> 2NH3, if 20.0g of hydrogen reacts: ...a. How many grams of ammonia are produced? ...20.0g H2...|1 mol H2..|2 mol NH3.|...17.04g NH3 ......|2.02g H2.| 3 mol H2..|...1 mol NH3 112.5 grams of ammonia are produced...
  5. V

    Bunch of Equations and Stoichiometry

    I'm totally stuck; please if you could get any of these solved so that i can go ahead with the hints and help myself out... It's tragic! -A cube of redwood 3.00 cm on an edge weighs 11.8 g. What's its density? -A beaker containing 4.00 x 10^2 cm^3 of a liquid having a density of 1.85 gcm^3 is...
  6. S

    Stoichiometry, Part II (and Percentage Yield)

    Please (pretty please) check all of my work! 1) In an oxidation reaction, ethanol (C2H5OH) is converted to a ethanoic acid (C2H4O2) with a percentage yield of 70%. If you start the reaction with 360g of ethanol, how many grams of ethanoic acid would you expect to produce? Stoichiometry is...
  7. S

    Calculate CaCO3 Mass: Stoichiometry Help for Decomposition Reaction

    a. A sample of CaCO3 decomposes when heated to form calcium oxide and carbon dioxide. 1.5432 g of CO2 are released in the reaction. Find g of CaCO3 in the original sample. CaCO3 --> CO2 + CaO 1.5432 g CO2*(1 mol of CO2/44.01 g) = 0.035065 mol of CO2*(1 mol CaCO3/1 mol CO2) = 0.035065 mol...
  8. D

    Solve Stoichiometry Problems with HCl and Marble

    A little stoichiometry... Here's all that was given: A container of HCl spilled on a marble table surface. The marble contains calcium carbonate, which reacts with the acid to produce calcium chloride, carbon dioxide and water. a) If 500ml of 0.2 M acid spilled, what mass of calcium...
  9. G

    Stoichiometry Help: Calculating Moles & Grams of O

    Hey could you guys tell me whether I am on the right track with this or not. First Problem: A tablespoon of sugar, C_1_2H_2_2O_1_1, weighs 2.85g. A.) How many moles of sugar are there in a tablespoon? Do I calculate the molar mass of sugar in grams and then divide 2.85g by the molar...
  10. S

    Stoichiometry practice questions

    Does anyone know any sites with stoichiometry. I need to practice some questions.Site with practice problems and example that are easy to follow?
  11. S

    How to Calculate Mass in Stoichiometry Problems?

    1. Aluminum chloride (15.0g) + sodium hydroxide (15g) = double displacement reaction.Predict mass of aluminum hydroxide produced. What mass of the excess reagent remains unreacted? 2. What mass of copper(II) sulfate pentahydrate is needed to prepare 150.0 mL of a 0.125mol/L solution...
  12. E

    Moles 0_2_(g) React to Produce H_2O_(g)

    How many moles of H_{2}O_{(g)} are produced when 9.6 mol of 0_{2}_{(g)} react?
  13. D

    Two unknwon factors in this stoichiometry problem

    Can someone help me with this? What volume, cm³, would 36.25g of C_4H_1_0 occupy at 85.20 kPa and 108 celsius? So I am assuming i should use the ideal gas equation, PV = nRT, and isolate V so i get: V=\frac{nRT}{P} heres where I am stuck, how do i solve for "n" when only...
  14. A

    What Is Stoichiometry in Chemistry?

    I have to define stoichiometry. Any one know a good definition for it? I'm reading a sentence it was used in "Many combinations of mono and trivalent cations yield crystals of the same stoichiometry and structure" As well does anyone know a good definition of synthesis. Is it simply the...
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