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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partially cancelling spectator ions

Is it possible to partially cancel spectator ions? Suppose in the ionic equation the same ion appears on both sides but with different coefficients.
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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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39 views

What is the cause of decrease in volume of gaseous mixture in the following problem? [closed]

I am studying Gaseous State. The problem says: A mixture of gas contains $\ce{N2}$ and $\ce{C2H2}$. $\pu{20 \\mL}$ of this mixture is added to $\pu{70\\mL}$ of $\ce{O2}$ and combustion is allowed to ...
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46 views

Will the volume occupied by a mixture of nitrogen and water be same as the volume occupied by them individually?

I am currently studying gaseous state and I encountered the following problem. A container with a volume 3 liter holds $\ce{N2(g)}$ and $\ce{H2O(l)}$ at $\pu{29 ^\circ C}$. The pressure is found to ...
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2answers
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Proust's law/Laws of definite proportion [closed]

As per laws of constant proportion/Proust's law,Ratio of elements by mass is always constant. But in case of H2+O2 →H2O Here when the chemists might have measured H2 and O2 individually they might ...
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1answer
50 views

Balancing chemical reactions, issues of Gauss's elimination method [duplicate]

I am trying to balance some chemical reactions by using the Gauss' elimination method and I noticed that this method does not work if the creation of a matrix with exactly one degree of freedom is not ...
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2answers
37 views

How do I do stoichiometry for 2 limiting reactants

The Drano reaction produces sodium aluminate along with hydrogen gas. If a typical container of Drano weighs 500 g which is 35% by weight by weight sodium (l) hydroxide and 2.5% by weight aluminum, ...
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1answer
35 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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1answer
40 views

Why are yields of some chemical reactions so dependent on the stoichiometry of the reagents? [closed]

Back in chemistry class in high school I was working with a partner doing a chemical reaction. We measured the amounts of reagents well, but not perfect, and our yield suffered greatly. On the other ...
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Methods and observations that help you achieve complete decomposition of a compound in decomposition analysis [closed]

Different chemicals decompose in different ways to give different observations, but they usually involve heating the compound to high temperatures. My question is that what are your lab techniques ...
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1answer
30 views

What value should I use for P in the ideal gas equation for an unknown molar quantity?

I did a chemistry lab, in which baking soda and vinegar were reacted in a ziplock bag, and I was to calculate the proper quantity of reactants to fill the bag with CO2. The molar quantity of gas was ...
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How to find the molecular formula for a hydrocarbon compound from known combustion products?

What is the molecular formula of a compound containing only carbon and hydrogen if combustion of $1.05~\mathrm{g}$ of the compound produces $3.30~\mathrm{g}~\ce{CO2}$ and $1.35~\mathrm{g}~\ce{H2O}$ ...
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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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1answer
62 views

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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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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1answer
45 views

Why do we use coefficients for RFM (relative formula mass) in atom economy? [closed]

Usually when calculating using moles = mass / RFM, the coefficient is not multiplied by a compound's RFM to calculate RFM. But in calculations for atom economy, the (balanced) coefficient of a ...
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1answer
178 views

Reaction between copper(II) iodate and iodide

I was attempting the following question from IChO 1989, which involved balancing of redox equations. One may just expect this to be a typical iodate-iodide redox reaction, usually employed in ...
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Balancing the reaction equation for the oxidation of lead(II) sulfide with ozone

While I was reading about the chemical reactions of ozone, I came across this reaction. $$\ce{PbS + 4O3 -> PbSO4 + 4O2}$$ Though the reaction seems well balanced, but when I attempted to balance ...
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1answer
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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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Two different answers obtained by balancing this chemical equation!! Somehow [duplicate]

This is the concerned equation: $\ce{ XeF4 + H2O -> Xe + XeO3 + HF + O2}$ This can be balanced as $\ce{6 XeF4 + 12 H2O -> 4 Xe + 2 XeO3 + 24HF + 3 O2}$ or $\ce{5 XeF4 + 10H2O ->3 Xe + ...
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1answer
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Is the kilogram still consistent with the old definition?

My old understanding was that a gram is the amount of mass in a cubic centimeter of water. But then I recently learned that the second was redefined to be some 9 billion cycles of a Caesium atom. ...
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1answer
374 views

What do the half-reactions need to be for balancing a redox reaction in an acidic medium?

Balance the following reaction: $$\ce{CuS + SO4^{2-} -> CuO + SO2}$$ Below, the number mentioned in the parenthesis is the oxidation number of sulfur. I have found out that the oxidation half-...
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817 views

Determine the amount of substance of calcium chloride used

Determine the amount of substance (in moles) of calcium chloride used in this lab. (Hint: $0.20\rm~M$ means $0.20\rm~moles:1~L$) I made $96$ milliliters of $\ce{CaCl2}$ which would be $0.096\rm~L$...
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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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1answer
93 views

How to calculate the equivalent mass of Na2S2O3? [closed]

Let us consider the following reaction $$\ce{I2 + 2 Na2S2O3 -> 2 NaI + Na2S4O6}$$ Now, in order to calculate the equivalent mass of $\ce{Na2S2O3}$, first I need to calculate it's $n$-factor which ...
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Complete combustion of mixtures

I am working on my scholarship exam practice (around high school and first year university level). I could actually solve the problem below but my solution is pretty time consuming. It would be ...
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1answer
122 views

How to calculate the equivalent weight of KMnO4?

Let us consider the following reaction $$\ce{2 KMnO4 + 16 HCl → 2 KCl + 2 MnCl2 + 8 H2O + 5 Cl2}$$ Now, in order to calculate the equivalent mass of $\ce{KMnO4}$, first I need to calculate it's $n$-...
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209 views

Why the concentration with respect to time equation of a first-order reaction does not depend on the stoichiometric coefficient of reactant?

According to my Chemistry textbook (Chemistry by Raymond Chang 10th edition, pg 570), for a first-order reaction of the type $$\ce{A->product}$$ the rate is $$rate=-\frac{[\Delta A]}{\Delta t}$$ ...
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50 views

Finding the sum of coefficients of the reaction

What is the sum of the coefficients $(a + b + c)$ in the following reaction? $$\ce{x Zn + y HNO3} -> {a Zn(NO3)2 + b H2O + c NH4NO3}$$ Here if the equation is balanced we get 1 mol of $\ce{Zn}...
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Shouldn't the “law of conservation of mass” prevent equations from being unbalanced in the first place? [closed]

How is it that a chemical reaction produces an equation, that is essentially an impossibility, according to the law of conservation of mass? If the law is true, shouldn't all chemical reactions ...
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123 views

Weight of sodium acetate required to get to certain pH

How many grams of $\ce{CH3COONa}$ we need to dissolve in $\pu{2.50 L}$ of water to get a solution with $\mathrm{pH} = 9.00$? Given $K_\mathrm{a}(\ce{CH3COOH}) = 1.75\cdot 10^{-5}$ Like solving a ...
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1answer
110 views

How does the pH of solutions of salts in which the cation is acidic and anion basic, depend only on the relation of their constants?

My book is not very explanative about it, I'm trying to get the equation: $$[\ce{H^+}]=\sqrt{K_\mathrm{w}\times\frac{K_\mathrm{a}}{K_\mathrm{b}}}$$ but I didn't succeed, can someone explain the ...
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Equivalents of Oxalic acid

In this question the answer key given is A and C. But i think that D should also be wrong because equivalents = molecular mass / n factor = $\frac{90}{2} = 45 \neq 40 $ I believe I am correct but I ...
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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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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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58 views

Determining amounts of product and excess reagent remaining post reaction

$$\ce{2FeS2 + 11/2 O2 -> Fe2O3 + 4 SO2}$$ Mass of $\ce{FeS2}$ is $\pu{600 g}$ and mass of $\ce{O2}$ is $\pu{800 g}$. Find the amounts of $\ce{Fe2O3}$ and $\ce{SO2}$ and the remaining amount of ...
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Is there a specific chemical reaction between capsaicin and casein? Is there a stoichiometric relationship between them? [closed]

I am trying to establish the reaction between capsaicin and casein in order to neutralize the effects of the capsaicin. Therefore, I must determine if there is a reaction and a stoichiometric relation....
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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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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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1answer
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Finding simplest formula of a compound with following specifications

I ran into the following problem, wherein I'm asked to find the simplest formula of a compound containing $50 \%$ of element $X$ (atomic wt. 10) and $50\%$ of element $Y$ (atomic wt. 20). I know ...
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1answer
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Help with question about mols in reactions

Consider the following reaction $$\ce{4H2O + 5I2O4 -> 8HIO3 + I2}$$ If 0.167 mol of $\ce{H2O}$ is added to 0.200 mol of $\ce{I2O4}$ what amount (moles) of $\ce{HIO3}$ can be formed, it ...
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How to deterime the number of equivalents of Grignard reagent used for this reaction?

I know that the amount of substance of Grignard reagent used is 5 moles. But the answer given is 2. Is this anything to do with 'equivalents'?
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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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What does it mean to calculate hardness in terms of ppm of calcium carbonate? [closed]

PPM means per part million or milligram per litre of solution.Calculation of ppm for a given compound say $x \pu{gms}$ of $\ce{Ca(HCO_3)}$ in 1 liter of water would be done like $$ppm= \frac{1000\...
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439 views

Finding all Chemical Reactions Given Products and Reactants

Suppose only a set of chemical formulas is given. How can you find all mathematically possible chemical equations whose educts and products are only from this set? Take e.g. the set $\{ \ce{C, H2, O2,...
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1answer
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Why coefficient doesn't change amount of substance

$\ce{3Mg + 2As -> Mg3As2}$ ($10\ \mathrm g$ of $\ce{Mg}$ and $10\ \mathrm g$ of $\ce{As}$) I don't understand why coefficient doesn't change the amount of substance, here's what I did: $n_{\ce{Mg}...
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2answers
101 views

Derivation of Gibbs free energy formula

Okay, so I'm trying to derive an important formula which states that - ∆G(r) = ∆G° + RTln( RQ ) where ∆G(r) is the instantaneous rate of change of Gibbs energy with ...
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How to calculate the equilibrium constant for nitrogen, hydrogen, and ammonia?

$\pu{2 mol}$ of $\ce{N2}$ is mixed with $\pu{6 mol}$ of $\ce{H2}$ in a closed vessel of $\pu{1 L}$ capacity. If $50\%$ of $\ce{N2}$ is converted into $\ce{NH3}$ at equilibrium, what is the value of $...
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How many liters of hydrogen gas is produced per gram of aluminium?

How many liters of $\ce{H2(g)}$ at STP is produced per gram of $\ce{Al(s)}$ consumed in the following reaction? $$\ce{2Al(s) + 6HCl(aq) -> 2AlCl3(aq) + 3H2(g)}$$ Express your answer to four ...
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1answer
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How to balance the reaction equation of potassium permanganate, calcium oxalate, and sulfuric acid step by step?

I have been desperately trying to balance the following equation, and finally (ultima ratio) used an online program to get it done (posted the same question there as well). $$\ce{KMnO4 + CaC2O4 + ...