Questions tagged [stoichiometry]

Stoichiometry refers to the relationship between the amounts of substances of the reactants and the amount of substances of the formed products. This tag should be used for specific questions about chemical reaction equations.

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On what factors does the true reaction Stoichiometry depend when there are multiple valid options?

Consider the following unbalanced reaction: $$\ce{XeF4 + H2O -> Xe + XeO2 + HF + O2}$$ There are six variables to be solved, but only four equations linking them. I solved the set of equations ...
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59 views

What does “at%” mean and how it differs from “mol%”?

Sorry if my question is a bit obvious, but for some reason I'm getting confused with the percentages in this question: Concentration of $\ce{A}$ is $\pu{80 at\%}$ and concentration of $\ce{B}$ is $...
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Molar ratios not leading to complete reaction in Schweizer's reagent production

In my home lab, I've reacted $\ce{Cu(OH)2}$ with aqueous ammonia to produce Schweizer's reagent. However, I'm surprised by the amount of ammonia required to react with this amount of $\ce{Cu(OH)2}$. ...
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Mass of H2 in a balloon

Question A balloon of diameter $\pu{2 m}$ has a volume of $\pu{4190 dm^3}.$ It floats since it is given an up thrust equal to the mass of air it displaces. (Given: average $M_\mathrm{r}$ of ...
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134 views

Using Avogadro's law to find gas volumes

An important step in the preparation of sulfuric acid involves the production of sulfur trioxide ($\ce{SO3}$) from sulfur dioxide ($\ce{SO2}$) and oxygen. $$\ce{2 SO2 (g) + O2 (g) -> 2 SO3 (g)}...
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172 views

Why does my eudiometer have this excess volume at the top?

It looks like this: The measurements start at 2 mL and the volume remaining in the top seems to be greater than 1 mL. What is the purpose? I am trying to measure hydrogen gas.
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Stoichiometry based on addition of simultaneous equilibria

I read on another equilibrium question that if two equilibria occur at the same time, then it is not accurate with actual stoichiometry to add the two equations and multiply the equilibrium constants $...
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Chain reaction vs single reaction

I am considering the following chain reaction: $$\begin{align} \ce{A_0 + B <=>[$N\cdot k_+$][$k_-$]A_1\\ A_1 + B <=>[$(N-1)\cdot k_+$][$2\cdot k_-$]A_2\\ A_2 + B <=>[$(N-2)\cdot k_+$]...
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224 views

Where to find good worksheets for balancing chemical equations

I am preparing for the Chemistry SAT in a couple of weeks. I am looking for worksheets like this that will give me practice balancing complex chemical equations with lots of compounds. Is there any ...
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Problem regarding failure of equivalence concept

Chile salt peter, a source of $\ce{NaNO3}$ also contains $\ce{NaIO3}$. The $\ce{NaIO3}$ can be used as a source of iodine, produced in the following reactions. \begin{align} \ce{IO3- + 3 HSO3- &...
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223 views

Calculating a theoretical degree of polymerisation of ethylene oxide

This is the problem: Researchers add 88 grams of ethylene oxide. This reacts fully to 92 grams of poly ethylene oxide. Calculate the degree of polymerisation. I thought: molecular weight of ethylene ...
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905 views

Why are the stoichiometric coefficients used as exponents in the chemical equilibrium constant?

From what I can ascertain, the formulation of the chemical equilibrium constant is somewhat arbitrary. I don't understand the motivation for putting the stoichiometric coefficients in the exponents. ...
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701 views

Variation in pressure for a gas phase reaction

Predict how the total pressure varies during the gas-phase reaction $\ce{N_2}(g)+ 3 \ce{H2}(g) \rightarrow 2 \ce{NH3} (g) $ in a constant volume container. Reference: Atkin's Physical Chemistry, ...
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Application of limiting reagents and acid-base stoichiometry

I'm having a bit of trouble with the latter questions of this problem. $\pu{15.0 mL}$ of $\pu{1.4 M}$ $\ce{HCl}$ was mixed with $\pu{1.00 g}$ of $\ce{CaCO3}$ until all the solid had dissolved. The ...
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Balancing molecular and net ionic equations for reactions

Source:'Chemistry: The Central Science 11th edition' by Brown. Ch.4, 4.53: Question: Write balanced molecular and net ionic equations for the reactions of: chromium with hydrobromic acid; ...
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452 views

Degree of Hardness Numerical

To remove the temporary hardness from $5\ \mathrm L$ of $\ce{H2O}$ $5.6\ \mathrm{mg}$ of lime is required. Calculate the degree of hardness due to $\ce{Ca(HCO3)2}$ present in water. My attempt: $$ \...
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94 views

What is the point of POAC? Why can't one just balance?

I have been studying the principle of atomic conservation, but have not understood why it even exists. For example: What mass of $\ce{O2}$ is produced by 1.23 g of $\ce{KClO3}$? Couldn't this ...
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51 views

Stoichiometry yielding negative volume

$15~ \textrm{mL}$ of $4 ~\textrm{N}$ hydrochloric acid, $ 25~ \textrm{mL}$ of $2~ \textrm{M}$ $\textrm{H}_3\textrm{PO}_3$ and a certain volume of $2.5~\textrm{M}$ sulphuric acid are mixed together and ...
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204 views

Validity of Law of Equivalence

Is law of equivalence valid for partial displacement reactions? 【I found this in my textbooks: According to the law of equivalence, whenever two substances react, the equivalents of one will be equal ...
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51 views

Can I approximate the CO concentration of a combustion product, if I know the CO2 and O2 concentration?

Assume I have the product (exhaust gas) from a combusted air/petrol mix. The mixing ratio was richer than stoichiometric (i.e., air:fuel < 14.67 in this case), so there was no excess of oxygen. I ...
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Do we use volumes of both solutions if they have different densities to find cocentration of ions

So essentially lets say I am given a mixture of hexane, water and nickel chloride(masses also given) in a beaker, and am asked to find the concentration of the chloride ions in the aqueous layer of ...
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904 views

Moles of Sodium Peroxoborate

The question involves the addition of $\pu{0.15 g}$ of an already prepared sample of sodium peroxoborate which is added to $\pu{100 mL}$ of $\pu{1 M}$ $\ce{H2SO4}$ and $\pu{2 g}$ of $\ce{KI}$. The ...
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253 views

Parts Per Million

I am trying to calculate how many milliliters of a solution I cannot exceed to create $\pu{200ppm}$ in the air of isopropyl alcohol. The $\pu{26ml}$ bottle of solution is 70% isopropyl alcohol. Using ...
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63 views

Molar ratio of two oxides of the same metal

A certain "metal oxide" is made of the oxides $A$ and $B$ of the same metal. In the oxide $A$, the metal is divalent, and in B, the metal is tetravalent. By reduction with hydrogen of a quantity $a$ ...
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76 views

Can equivalent mass be more than the molecular mass? Can it be applied to radical reactions?

Consider a reaction involving radicals: $$\ce{CH3^. + Cl^. -> CH3Cl}$$ Is the definition of equivalent mass applicable here? If yes, how? Are there reactions where equivalent mass of a reagent ...
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45 views

Why are there so many reactions for the discharge of LiCoO2?

I've just managed to understand a bit the meaning of having the notation of 0.5 in a molecular formula, when I found a set of multiple notations for the same discharge process that started to confuse ...
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I'm not sure I understand the stoichiometry of this mechanism

I was going through the experimental mechanism of nickelocene synthesis, and I looked through the notes and it said that there would be $\frac12$ $\ce{NiCl2}$. I'm sort of confused by the $\frac12$. ...
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76 views

Stoichiometry in Gas-Solid Flow System

I am a bit confused on how to account for the stoichiometry of a reaction as follows: $$\ce{A}(s) + \delta \ce{B}(g) \ce{->} \ce{C}(s) + \delta \ce{D}(g)$$ The solid $\ce{A}$ is stationary in the ...
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702 views

Molar heat of reaction for water in a neutralization reaction

I have a simple lab problem: $30\ \mathrm{mL}$ of $1\ \mathrm{mol/L}$ $\ce{H2SO4}$ reacts with $50\ \mathrm{mL}$ of $1\ \mathrm{mol/L}$ $\ce{NaOH}$ in a neutralization reaction as per the following ...
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3k views

Explanation of the law of equivalence

According to the law of equivalence, the number of equivalents of each reactant and product in a reaction are equal. Why is this the case?
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Stoichiometry reactions for water clarification

If ferric chloride was added to a water sample which had calcium bicarbonate alkalinity present, would the reaction be a ‘stoichiometry reaction’ or a ‘limiting reagent reaction’? For example, if 1 g ...
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Calculate the percent composition of a sodium carbonate/sodium bicarbonate mixture

In a lab, we titrated a solid mixture of sodium carbonate and sodium bicarbonate with $\pu{0.1 M}\ \ce{ HCl}$. We are asked to calculate the percent composition by mass of sodium carbonate and sodium ...
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39 views

Balanced equation for Schweizer's reagent production?

In Thompson's Illustrated Guide to Home Chemistry Experiments the chemical formula for Schweizer's reagent is represented as $\ce{[Cu(NH3)4](OH)2}$ (although Wikipedia represents it as $\ce{[Cu(NH3)4(...
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Question based on finding impurity of a sample of Sodium bicarbonate

12.5g of commercial sodium bicarbonate gives 3 g of carbon dioxide. What is the percentage in purity in the sample? $$\ce{2NaHCO_3 -> Na_2CO_3 + CO_2 + H_2O}$$ I have solved this question, but I ...
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How do you find the heat capacity ratio of combustion products?

For example, if gaseous oxygen $(O_2)$ and paraffin wax $(C_{32}H_{66})$ were to stoichiometrically combust at STP, how would one go about finding the heat capacity ratio ($\gamma={c_p \over c_v}$) of ...
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73 views

Finding initial mole fraction of ammonia in ammonia-hydrazine mixture using thermodynamic parameters before and after thermal decomposition

A mixture of $\ce{NH3}$ and $\ce{N2H4}$ is placed in a sealed container at $\pu{300 K}$. The pressure within the the container is $\pu{0.6 atm}$. The container is heated to $\pu{1000 K}$ where the ...
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Why decanted solution should be colorless when determining formula of unknown chloride?

I was following the guide “Stoichiometric Determination: Empirical Formula of Copper Chloride”. Under the Procedure section the following reaction is given: Producing solid $\ce{Cu}$ from a $\ce{Cu(...
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101 views

Equivant mass of double salt

What is the equivalent mass of double salt like dolomite? And what if the double salt is hydrated? Is a double salt taken as a single unit while equating the gram equivalent in any reaction? For ...
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Finding molarity of hyposulfite solution used in titration

$\pu{0.1 g}$ of $\ce{KIO3}$ is treated with excess $\ce{KI}$ solution. The liberated iodine required $\pu{44 ml}$ of $x$ molar hypo solution. Calculate the value of $x$. I have used the equivalent ...
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58 views

How can normalities be interchangeably used?

So I was doing the following question on stoichiometry . The part $\pu{1.80N}\ \ce{HCl}$ can also be written as $\pu{0.9 N}\ \ce{ H_2SO_4}$ but I don't understand why . $\pu{10 g}$ sample of 'gas ...
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What type of acid (and how much) needed to generate Chlorine Dioxide gas when added to Sodium Chlorite (for odor removal)?

I have several lbs of Sodium Chlorite (flakes), which I would like to use to generate Chlorine Dioxide gas in order to remove odors from rooms, autos, boats, etc. There are commercial products sold ...
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About the percentage yield and purity

I was wondering why all of the percentages like mass percent composition, percentage yield and percentage purity are calculated using masses. Wouldn't it make more sense to use number of moles of the ...
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Gravimetric analysis

In a gravimetric determination of phosphorus an aqueous solution of dihydrogen phosphate ion is treated with the mixture of ammonium and magnesium ions to precipitate magnesium Ammonium Phosphate. ...
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Theoritical amount of Sodium Bicarbonate

I have to find the theoretical amount of sodium bicarbonate. The steps I followed in order to produce it are: 15g $\ce{NaCl}$ are added to a beaker. Then we add 87.5 mL of $\ce{NH3}(12M)$ We add 115g ...
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38 views

Is this problem doable with the information given?

Can I solve this problem without knowing any starting amounts? An element $\ce{X}$ forms iodide ($\ce{XI3}$) and chloride ($\ce{XCl3}$). The iodide is quantitatively converted to the chloride when it ...
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2k views

Stoichiometry consumed/generated

NaHCO3(aq) + H3C6H5O7(aq) = H2O(l) + CO2(g) + NaC6H5O7(aq) 9 NaHCO3(aq) + 8 H3C6H5O7(aq) = 14 H2O(l) + 3 CO2(g) + 9 NaC6H5O7(aq) List at least 2 types of reactions that the equation in question #2 ...
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240 views

'Rate' in the rate law

I am slightly confused about what the rate is that is given by the rate law. Is it the rate of reaction (I.e. the rate of loss of reactant or formation of product divided by its stoichiometric ...
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Recycling Reactor

Given the synthesis reaction of methanol: $$\ce{CO2 + CO + 5H2 -> CH3OH + H2O}$$ In a reactor with a recycle stream contains all 4 components. When calculating the energy of reactants, do we ...
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Do you divide by 16, or by 32 when finding the amount of moles in Oxygen gas (magnesium oxide experiment)?

Magnesium + oxygen gas makes magnesium oxide. The formula for this is 2Mg + O2 --> 2MgO. If we had 0.18g of Magnesium and 0.18g Oxygen, to find the moles of both masses you divide by the molar mass. ...
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318 views

Finding the percent by mass of an unknown substance

I'm doing some chemistry homework and a the problem in question goes as follows: "A student performs an experiment to determine the percentage by mass of $\ce{MgCl2}$ in a $\pu{2.94g}$ sample of a ...