What is Stoichiometry: Definition and 164 Discussions

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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  1. mishima

    High School Chemistry: Stoichiometry Readings?

    Hi there, I've taught high school stoichiometry (limiting reactant, theoretical yield, etc) for about a decade now focusing on both math (such as mol reactant to grams product) and related lab techniques (maximizing percent yield). I would like to expand my curriculum with some good readings...
  2. Hamiltonian

    Chemistry Calculating the empirical formula from a percentage composition

    Let the empirical formula be ##Na_x S_y O_z## then we can concude $$\frac {29.11}{100} = \frac{xM_{Na}}{xM_{Na} + yM_S + z M_O}$$ $$\frac {40.51}{100} = \frac{yM_S}{xM_{Na} + yM_S + z M_O}$$ $$\frac {30.38}{100} = \frac{zM_O}{xM_{Na} + yM_S + z M_O}$$ where ##M_{Na} = 23, M_S = 32,M_O = 16##...
  3. WMDhamnekar

    MHB Stoichiometry: Comparing Ion Numbers in Different Sample Solutions

    Which sample contains the greater number of ions? 1) $100cm^3$ of 0.05 mol $dm^{-3} CuS$(cupric sulfide) 2)$100 cm^3$ of 0.20 mol $dm^{-3} MgSO_4$ magnesium sulfate 3)$50 cm^3$ of 0.40 mol $dm^{-3} RbCl$ rubidium chloride 4)$100 cm^3$ of 0.20 mol $dm^{-3} CaCl_2$ calcium chlorideHow to...
  4. WMDhamnekar

    MHB Stoichiometry question in chemistry

    Hi, 10.0 dm³ of sulfur dioxide is reacted with 6.0 dm³ of oxygen according to equation below. 2SO₂(g) + O₂ → 2SO₃(g) What volume of sulfur trioxide in dm³ is formed? If any member knows the correct answer to this question may answer to this question. Please answer with your...
  5. U

    Chemistry Why does the solution divide by two in Mole Stoichiometry?

    So essentially I followed pretty much what is in the picture here in this solution. https://www.slader.com/textbook/9780134162430-chemistry-a-molecular-approach-4th-edition/242/exercises/79/ My question is essentially why does he do the 0.07XXX mol f2 * 2mol clf3/3mol f2 * 92xx g/2mol f2 =...
  6. WMDhamnekar

    MHB Stoichiometry Question: Seeking Correct Answer | Website Name

    Hi, If any member knows the correct answer to the following question on stoichiometry, may reply to this question.
  7. David Cameron

    How About Booger Problems in Reaction Stoichiometry

    I have taught introductory general chemistry to engineering majors for over 30 years. Upon one occasion, a student told me "I sort of like the homework ... except the booger problems that I can't do." But it is exactly those problems, the more difficult type of problems, that give the student...
  8. K

    Investigating the Stoichiometry of Reactions 1 & 2

    Cl2(g) + 2I–(aq) -->I2(aq) + 2Cl–(aq) (reaction 1) [2S2O3^(2-)(aq) + I2(aq) --> S4O6(2-)(aq) + 2I–(aq) (reaction 2) Why isn't n(I2)(reaction 2)=2n(S2O3^(2-))(reaction 2). I don't see why this is wrong. <edit: remove size and italics>
  9. dRic2

    Question about simple kinetics and stoichiometry

    Hi, I'm having trouble with this simple reaction (1): $$A + A → I$$ with ##R = kC^2_A## I'm assuming it takes place in a Batch reactor so the mass balance should yield: $$\frac {dC_A} {dt} = -2R = -2kC^2_A$$ But, as I recall (I should be wrong though)...
  10. C

    Finding volume of one compound using Stoichiometry equation

    Homework Statement I am having a problem finding the volume of one compound while having the molarity and volume for another using a balanced equation. This is the problem statement: What volume in mL of ammonium carbonate is needed to react completely with 200.0 mL of 1.500 M silver (I)...
  11. L

    Can I Use Stoichiometry to Predict the Products of a Reaction?

    Homework Statement Homework Equations M = n/L[/B]The Attempt at a Solution My answer is A) 1.02 M but I am not sure if i did this right. Can someone explain why this might be right or wrong? I got moles of Al(NO3)3 =0.0393 moles I got moles of Ca(NO3)2 = 0.0426 moles by multiplying...
  12. L

    What error did i make? (stoichiometry)

    So my answer is off by about 1.16 grams and am wondering if i did something wrong? Question: What mass of silver iodide precipitates when 25.0 ml of 2.30 M silver acetate solution is mixed with 10.0 ml of 2.35 M calcium iodide solution? Given: 0.025 L of 2.30 M AgC2H3O2 = 0.0575 mols acetate...
  13. C

    Question Related To Volume Strength Of H2O2.

    1. Question Statement and details : 500 mL of 56V H2O2 is kept in an open container due to which some H2O2 is decomposed and evolves 8gm O2 simultaneously, during the process some H2O also vapourizes.Due to all these changes final volume is reduced by 20%. Find final volume strength of H2O2...
  14. T

    What is the percentage of Fool's Gold in the original sample?

    Homework Statement Joshua has been gold panning and extracts a mixture of silicate stone and shiny gold-like particles. However Nkosi says these are Fool's Gold i.e Chalcopyrities (Cu Fe S2). They decide to find out how much iron is in the sample by: -Grinding a 30.00g sample to a fine powder...
  15. Aafia

    Calculating Volume in dm³: Solving the Equation 2KClO3 -----> 2KCl + 3O2

    Homework Statement What volume in dm³ of KCl is obtained in the following equation 2KClO3-----> 2KCl + 3O2? Homework Equations None The Attempt at a Solution I suppose there is not enough data and according to equation it is 44.8dm³. But my book says 2 dm³, I don't understand how?
  16. K

    MHB How Long to Empty Lake Erie with a Cone Cup?

    Lake Erie holds 116 cubic miles of water. Suppose you start dumping out the entire volume of Lake Erie using a cone cup. A typical cone cup has a diameter of 2.75 inches and a height of 4 inches. About how long would it take you to empty the lake if you could dump out one cup per 2 seconds? Use...
  17. S

    Stoichiometry: Identify the metal and formula of it

    Homework Statement All of the lanthanide metals (La through Lu) react with HCL to form compounds having eithe the formula MCl2, MCl3, MCl4, (where M represents the metallic element). Each metal forms a single compound. A chemist has a 0.250g sample of a lanthanide metal, and she wishes to...
  18. Aafia

    Mg metal reacts with HCl to produce hydrogen gas?

    1. The problem statement, all variables and given/known Mg metal reacts with HCl to produce hydrogen gas. What is the minimum volume of HCl solution (27% by weight) required to produce 12.1 g of H2? Density of HCl solution is 1.14 g/cm3Homework Equations [/B] This question...
  19. T

    Calculating combustion temperature of mixture

    Hey guys, I'm trying to write a small article that very simply explains some of the math involved with a rocket engine. I'm not looking for a very accurate answer so I tried the following method 1) Stoichiometry on the fuel which was sugar and saltpeter and their respective enthalpies of...
  20. T

    Elementary reaction's order of reaction

    According to textbook, elementary reactions have an order of reaction equal to the summation of the stoichiometric coefficients. why is this so? And there is another problem, we can balance an equation in different ways and get different stoichiometric coefficient sets, for rates, which set is...
  21. Jefffff

    Best Method of Analyzing Experimental Percent Error

    Homework Statement I have performed a chemistry experiment where I analyzed how the diluting of two reactants with the same volume and initial concentration impacts the percent yield of a precipitate product. Thus my IV was concentration and my DV was percent yield. My question is what is the...
  22. H

    Easy Stoichiometry Concentration Problem

    1. A piece of iron was added to a beaker that contained 0.585 mol/L copper(II) sulfate, CuSO4(aq). The solid copper that precipitated was dried, and its mass was found to be 5.02 g. Some unreacted iron remained in the beaker. Calculate the minimum volume of the copper(II) sulfate solution. I...
  23. gfd43tg

    How Do You Modify the Stoichiometry for Sulfur-Included Food Waste Degradation?

    Homework Statement There's no problem statement, I'm doing this as part of my project For degradation of food wastes to methane, the general formula is given for food waste (without sulfur) ##C_{n}H_{a}O_{b}N_{c} + (n - \frac {a}{4} - \frac {b}{2} + \frac {3c}{4})H_{2}O \rightarrow (\frac...
  24. gfd43tg

    Modeling a reaction in SuperPro without stoichiometry

    Hello, I'm working on modeling a biological reaction with SuperPro. Right now, all I know about the reaction is the conversion. I don't have data on the stoichiometry, and I don't even think the stoichiometry of the reaction is known. Any idea how I might be able to model this kind of reaction...
  25. ptownbro

    Calculate mass of NaHCO3 when losing CO2 in experiement

    We have a homework problem that we are not sure is right. Need some help. Homework Statement The class ran an experiment where they were given 1.99 grams of NaHCO3 and 10.13 grams of HCl to create NaCl, H2O, and CO2. Before starting the experiment, what they were given weighed 12.12 grams...
  26. ptownbro

    Help w/ Molarity Question Related to a CuSO4 Solution

    We have a question on my daughter's homework I'm trying to help with and there is a part of it we have not been able to find support for to get to the answer. See below. We believe we've been able to answer parts "a" and "b" correctly, however, we're having trouble answering part "c" and were...
  27. ptownbro

    Stoichiometric relationship between liters and grams

    My daughter stump me on a question related to liters and grams in stoichiometry. Wondering if someone could help explain. First we know that 1 mole always eqauls 22.4 liters at STP. And 1 mole also always equals the selected element's atomic mass in grams on the periodic table. So... Let's...
  28. S

    Stoichiometry, find the mass of the product

    Homework Statement [/B] If 1.20 grams of salicylic acid is reacted with excess methanol, what mass of ester should you expect to achieve theoretically? Molar masses of.. salicylic acid is 138.13g/mol methanol is 32.05g/mol ester (methyl salicylate) is 152.16g/mol Mole ratio...
  29. Ameer Bux

    Struggling with Stoichiometry in High School Chemistry? Here's How to Master it!

    I am experiencing some difficulty grasping some chemistry concepts pertaining to stoichometry calculations. What are the best tips for studying this section of chemistry and how can i get an intuitive feeling for these concepts? Tips on high school chemistry in general are also welcome.
  30. Prashasti

    What is the mass of NH3 per cc in a solution of ammonia gas passed into water?

    Ammonia gas is passed into water, yielding a solution of density 0.93 g/cm^3 and containing 18.6% NH3 by weight. The mass of NH3 per cc of the solution is 1) 0.17 2) 0.51 3) 0.34 4) 0.68I solved it using the molarity equation. Molarity = 10xd/MM where, x - % by weight d - density MM -...
  31. L

    Calculating Mass in a Gas Stoichiometry Problem

    Hi all, While studying for my exam (and doing review questions) I came across a problem that I couldn't solve: 5. Zirconium metal and chlorine gas react to form zirconium (IV) chloride Zr + 2Cl2 = ZrCl4 a) What volume of chlorine gas must be used at 350 degrees Celsius and 50 kPa to produce...
  32. M

    How to Determine Mole Fraction and Mass Percent from Osmotic Pressure Data?

    Homework Statement When 0.32 weight/volume% of sucrose, MgSO4 and KNO3 mixture is dissolved in 997 g of H2O, the osmotic pressure at 25 deg Celsius is 1.25 atm. Calculate the mole fraction and mass percent composition of the original mixture if it contains 15% weight/weight KNO3. 2. Homework...
  33. A

    Find the Molarity of a Solution Using Concentrated Ammonia (28% by Mass)

    Homework Statement Calculate the molarity of a solution made by adding 35.5 mL of concentrated ammonia (28.0 % by mass, density 0.880 g/mL) to some water in a volumetric flask, then adding water to the mark to make exactly 250 mL of solution. (It is important to add concentrated acid or base...
  34. T

    Non-Stoichiometry & Partial Occupancies Explained

    Hello, I'd like to understand better the relation between non-stoichiometry and partial occupancies. Let's suppose for example that after an Xray analysys I find that in a material a site can be occupied by an atom of type 1 or an atom of type 2 with 50 % probability. Does it usually mean that...
  35. A

    How do you solve this stoichiometry problem? Is it possible?

    10.25g of a compound, including chlorine is then diluted. So there is 10.25g in the original compound, which is then diluted. 30mL of that solution is combined with an excess of AgNO3 to create 35.5g of AgCl. What is the mass percent of chlorine in the original compound/sample. I got 8.78g for...
  36. Illuvitar

    How Do You Calculate the Mass Percent of Fe3+ in Iron Ore Using Stoichiometry?

    Hello, I am in desperate need of help with setting up this problem and I would very much appreciate being steered in the right direction. 1. Homework Statement Find the mass percent of Fe3+ in a 0.0293g sample of iron ore if 13.25 ml of a .200 M stannous chloride solution is required to...
  37. P

    Exploring Equilibrium Constants & Kinetics: A Closer Look

    Consider the following generic equilibrium: aM + bN ⇌ cO + dP An equilibrium constant, K, can be defined as: $$K = \frac{[O]^c [P]^d}{[M]^a [N]^b}$$ But couldn't we also define another equilibrium constant similarly with coefficients that are in the same ratio as our original equation? For...
  38. D

    Ascorbic Acid Amount Calculation (stoichiometry/)

    1. Ascorbic acid in vitamin tablet Vitamin tablets with advertised contents including 750 mg ascorbic acid were analysed. A student took a whole tablet, crushed and dissolved all of it in water. He then diluted the tablet solution to a final volume of 250.0 mL. The student analysed 20.0 mL...
  39. S

    How much air does Sarah inhale while running?

    Homework Statement (The chemical equation is attached) Problem: Just before running, Sarah eats two oranges. Oranges provide her body with 25 grams of glucose which allows it to produce energy. The external temperature is 27 C, and atmospheric pressure is 102.3 kPa. While 21% of the air...
  40. R

    Stoichiometry terminology/chemical formula

    Hello All, Is it correct to write the compound U(As1-xSx)2 as UAs2-2xS2x?. So for x=0.5 the compound is UAs1S1. Thanks, Rajini.
  41. C

    What is the Molecular Weight of Each Compound in Moles/Grams for BaCl2 and NaF?

    Homework Statement BaCl2+ 2NaF -->BaF2 + 2NaCl Homework Equations See above...how to get 100g of the BaF2 product? The Attempt at a Solution Did molecular weight of each compound in moles/g
  42. P

    Stoichiometry: Calculating Reactant Mass from Product Mass

    I just wrote a test and will try to remember the question and how I answered it to the best of my ability.It was basically asking the find the mass of reactants from the mass of one of the products formed. My first step was calculate the moles of the product with known mass. Once I had the...
  43. L

    Using stoichiometry to determine empirical formula

    Homework Statement 1.000 g of vanadium is mixed with 8.000 g of bromine. After the elements react, some bromine is left over, along with a single compound that contains the two elements. The excess bromine is removed and allowed to react with excess sodium sulfite and excess sodium hydroxide...
  44. P

    Confusing Stoichiometry Question

    I got this question as an example question and I have no clue on how to solve part B Chlorine can be produced by the reaction: 2KMnO4 + 16HCl ->2KCl + 2MnCl2 + 5Cl2 + 8H2O (a)What mass of KMnO4 is required to produce 2.5 L of Cl2 gas measured at STP? For part A I got 7.05 g ( 0.044615...
  45. M

    Stoichiometry and other questions

    First of all I hope this is the right section of the forums My other was deleted because i posted at the wrong forum.
  46. z.js

    Is Stoichiometry Opposite of Avogadro's Number?

    Ever since I started stoichiometry I have had a silly idea that 6.02 * 1023 and 1.66 * 10-24 were opposites, so I tried it out: 1 amu g = (1 g) / (1 mol) amu = mol-1 amu*mol = 1 Is this correct? :smile:
  47. A

    How to Solve Simple Stoichiometry Problems Involving Solvents?

    Hey guys, I have two stoichiometry questions to do with solvents. Both of them are very simple and I am unable to complete them at the moment because of some silly error in my method, I am sure. Can you please explain the method and how to do the question in some detail? I really appreciate...
  48. C

    Solving Stoichiometry Problems: Titrating Fe(NH4)2(SO4)2*6H2O with KMnO4

    3) how many mL of the 0.10M KMnO4 are needed to titrate 0.5g of Fe(NH4)2(SO4)2*6H2O 4) Using half reactions, write the balanced Net Ionic Equation for the following in a basicls solution: KMnO4(aq) + Na2SO3(aq) + H2O(l) -> MnO2(s) + Na2SO4(aq) + KOH (aq) Reduction: ?? Oxidation: ?? 5)...
  49. T

    Stoichiometry reaction of FeCr2O4 with K2CO3

    1) K2CrO4 is produced by the reaction of FeCr2O4 with K2CO3 and O2 in a high temperature. This reaction also produces Fe2O3 and CO2. If 169 kg FeCr2O4 reacts with 298 kg K2CO3 and 75 kg O2 and so it produces 194kg K2CrO4 then calculate the efficiency of this reaction.2) The equations is: 4...
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