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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11
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2answers
21k views

Do coefficients matter in rate law?

For reaction $\ce{2A→B}$ (elementary step), according to the rate law, rate $= k [A]^2$. In some calculations, we use $k[A]^2$ as the production rate of B. Why isn't it ${1 \over 2} k[A]^2$? In this ...
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1answer
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More than one way of balancing a chemical equation

My textbook had this question on balancing chemical reactions Ozone reacts with nitric oxide to give nitrogen dioxide and oxygen gas Here's how I balanced it: $$\ce{O3 + NO -> NO2 + O2}$$ ...
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2answers
36k views

Simplest way to balance any chemical equation

In your opinion, what would be the simplest way to balance any size of the chemical equation? For example here is an equation: $$\ce{C12H26 + O2 -> CO2 + H2O}$$ I saw some ways by putting ...
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2answers
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Would 2 C₂ be 2 moles of diatomic carbon, or 4 moles of carbon?

Would molecules like $\ce{C2, H2}$, etc., be considered 1 mole of diatomic [element] or 2 moles of [element]?
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3answers
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Can a chemical reaction have two balanced equations?

I was recently studying Xenon compounds and read this reaction: $$\ce{6XeF4 + 12H2O -> 4Xe + 2XeO3 + 24HF + 3O2}$$ However this reaction can also be written as the following: $$\ce{4XeF4 + 8H2O ...
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1answer
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How can there be decimal subscripts in a molecular formula?

While learning about how batteries work I have encountered the following notation for a Li-ion cathode: $\ce{Li_{0.5}FePO4}$.[1] According to Wikipedia, the subscript number in a reaction equation ...
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2answers
555 views

Why is the rate of a reaction proportional to the concentrations of reactants raised to their stoichiometric coefficients?

Consider a gaseous state elementary reaction $$\ce{aA(g) + bB(g)} \overset{k_\mathrm{f}}{\underset{k_{\mathrm{b}}}{\ce{<=>}}}\ce{ cC(g) + dD(g)}$$ I know that for this reaction, $$\Delta G = \...
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3answers
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Law of mass action & Collision Theory

I don't understand why the stoichiometric coefficients of reactants and products are expotentialized in law of mass action. So I checked on Wikipedia. And this popped out: In the 1879 paper[9] the ...
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1answer
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Calculating pH in titration of monoprotic weak acid with strong base

$25.0\:\mathrm{ml}$ of $0.10\:\mathrm{M}$ $\ce{CH3COOH}$ is titrated with $0.10\:\mathrm{M}$ $\ce{NaOH}$. What is the $\mathrm{pH}$ after the addition of $30.0\:\mathrm{ml}$ $\ce{NaOH}$? In broad ...
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Why is potassium phosphate KH2PO4 in this reaction?

This is a continuation of this question because the first thing that came in my mind is that why potassium phosphate in this reaction is $\ce{KH2PO4}$ and not $\ce{K3PO4}$? In the wikipedia article ...
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1answer
6k views

What is an equivalent?

I want to know what is an equivalent and how is it different from equivalent mass. How to calculate and why is it used in chemistry for knowing concentration?
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1answer
173 views

Multiple solutions in the balancing of redox reactions

While looking at the reaction between potassium permanganate and hydrogen peroxide in the presence of sulfuric acid a friend and I were attempting to find a general equation to yield the coefficients ...
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1answer
900 views

What is the analogue of “molecule” for ionic compounds?

In a system, if we have $\pu{18 g}$ of $\ce{H2O}$ ($M_\mathrm r = 18$), we can say we have a mole of water molecules or $6 \times 10^{23}$ molecules. But in another system, if we have $\pu{342 g}$ of $...
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1answer
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Proof that Equilibrium Constant is a Ratio of Rate Constants

I have a question about this proof that shows the relationship between the rate constant and the equilibrium constant. In this proof, the assumption is that the reaction is $(a+b)$th order in the ...
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2answers
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How to determine the empirical formula for an unknown iron oxide?

I have to determine the empirical formula of an oxide of iron which has $69.9\%$ iron and $30.1\%$ dioxygen by mass in it. I have started as follows: For our convenience we take $\pu{100 g}$ of that ...
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1answer
210 views

Which ions are accounted for in total and net ionic equations?

There are a number of things I don't understand about ionic equations. First off, when you do net ionic equations, is it correct that you're only focusing on precipitates? The way I understood it, ...
2
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1answer
464 views

Is this definition of mole correct?

Chemical engineers define one mole as the amount of a substance which possess as many entities as $12\ \mathrm g$ of $\ce{^{12}C}$. The number of atoms in $12\ \mathrm g$ of $\ce{^{12}C}$ is $6.022 \...
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1answer
217 views

Maximum amount of P4 [closed]

$\ce{2Ca3(PO4)2 +6SiO2 +10C->6CaSiO3 +P4 +10CO}$ What is the maximum amount of P4 that can be produced from 1.0 kg of phosphorite if the phosphorite sample is 75% $\ce{2Ca3(PO4)2}$ by mass The ...
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1answer
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Are matrices a good way to do stoichiometry?

I was never taught in school to use matrices to balance my equation in stoichiometry. But I recently started to review my chemistry and, as I have taken linear algebra, I was suddenly struck by the ...
6
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1answer
1k views

Rate and order confusion

I just learned about rate and order... I just want to confirm if these three ideas are correct: If the first elementary step is the slow step, will the stoichiometric coefficients of the reactants in ...
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3answers
7k views

Law of Multiple Proportions: What is the significance of small whole numbers?

I'm new to Chemistry and in my textbook, it describes the Law of Definite Proportions (aka Proust's Law) and then goes on to describe the Law of Multiple Proportions. The example they give is carbon ...
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1answer
737 views

How are non-Stoichiometric compounds determined?

For solids where the compound contains defects, the stoichiometric equation deviates from the "pure" one. How are these compounds determined? I am looking in my chemistry book but I do not see ...
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1answer
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Relationship between rate equation and equilibrium constant

I have read mannaia's answer on the question of 'rate order and confusion', as well as Nicolau Saker Neto's answer to a related question. They have both been very helpful. As I understand, the ...
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3answers
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CH4 + O2 => CO2 + 2H2, what's wrong with it?

It says in my textbook that: $$\ce{CH4 + 2 O2 -> CO2 + 2 H2O}$$ which seems like a displacement reaction to me. Shouldn't the reaction be: $$\ce{CH4 + O2 -> CO2 + 2 H2}$$ since $\ce{4H}$ ...
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1answer
385 views

How do I determine whether it is the *ferrous* or *ferric* ion that is implied in this displacement reaction?

I'm supposed to write a balanced equation for: $$\ce{Iron(s) + copper(II) sulfate(aq) -> ?}$$ If I use Iron(II)/ferrous I get $$\ce{Fe + CuSO4 -> FeSO4 + Cu}$$ and if I use Iron(III)/ferric, ...
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2answers
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
25k views

What exactly does the term “gram atoms” mean?

The Wikipedia article on the mole states:  The term gram-atom (abbreviated gat.) has been used for a related but distinct concept, namely a quantity of a substance that contains Avogadro's number ...
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0answers
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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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1answer
317 views

Confusion with Law of Equivalence

Law of equivalence states that One equivalent of an element combines with one equivalent of the other. Equivalent of $\ce{Na}$ is $22.99$ and that of $\ce{O}$ is $8$. By the law of equivalence, $1$...
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3answers
15k views

C + O2 is equal to C + O, how is that possible

C + O = CO2 . This is because carbon has valency of 4 while oxygen has valency of 2. When they react the valencies are criss crossed which means we will get C2O4 but this is simplified to CO2. But ...
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1answer
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Can 1 mole of H2 react partially with one mole of O2?

I am currently studying stoichiometry (high school level) and we came across the following equation in school: $\ce{2H2 + 1O2 -> 2H2O}$ which is clear to me. We learned in school that reactions ...
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1answer
63 views

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. ...
4
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1answer
226 views

Why does multipying a scalar in both sides of a balanced chemical equation, change related quantities?

Stoichiometric coefficients appearing in a balanced chemical equation are unrelated to the actual concentration of reactant/products at any stage of a chemical reaction. They give information only ...
4
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1answer
445 views

Balancing by oxidation numbers method multiple atoms

In my Chemistry textbook, the rules for balancing a chemical equation using the oxidation-Number method are as follows: Assign oxidation numbers to all the atoms in the equation. Identify the atoms ...
4
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1answer
393 views

Dissolving limestone in HCl and then neutralising the solution with NaOH

$15.0~\mathrm{mL}$ of $1.4~\mathrm{M}\ \ce{HCl}$ was mixed with $1.00~\mathrm{g}$ of limestone (impure $\ce{CaCO3}$) until all the solid had dissolved. The solution was then transferred to a conical ...
3
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1answer
775 views

How Many mL of 1.0M HCl Would be Required to Completely Decompose Sucrose into Glucose and Fructose?

I am currently conducting an experiment into the glucose content of certain sports drinks. However, I have hit a roadblock. A majority of the drinks that I intend to test contain sucrose. I am ...
3
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1answer
4k views

Balancing the redox disproportionation of chlorine by half-reactions

I am having some difficulty balancing the following reaction using the half-reaction method: $$\ce{Cl2(g) -> Cl^{-}(aq) + ClO3^{-}(aq)}$$ My attempt at the problem: By determining oxidation ...
2
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2answers
273 views

Does a stoichiometric coefficient represent molecules or moles of a substance?

I understand that the one mole of atoms is equal to $6.02\times10^{23}$ atoms. However, when I used various resources to learn about stoichiometry, they showed me a balanced equation: $$\ce{2H2O->...
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2answers
419 views

Why is there an increasing solubility in water for chlorides, chlorates, perchlorates in that order?

According to Wikipedia $\pu{100 mL}$ of water dissolve at $\pu{25 ^\circ{}C}$ about $\pu{35 g}$ of $\ce{NaCl}$ (1), but about $\pu{79 g}$ of $\ce{NaClO3}$ (2), and around $\pu{210 g}$ for $\ce{NaClO4}$...
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1answer
6k views

Equation for reaction of tin(IV) and iodine to produce tin(IV) iodide

Tin(IV) iodide is prepared by direct combination of the elements. Add 2.00 g of granulated tin to a solution of 6.35 g of iodine. Write an equation for this reaction. Attempt: 1. Determine the ...
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4answers
5k views

How to find the empirical formula for an nitrogen oxygen compound from the given mass of nitrogen and the product?

$5.00~\mathrm{g}$ of nitrogen is completely converted into an oxide of nitrogen. The mass of the oxide formed is $19.3~\mathrm{g}$. The empirical formula of the oxide would be? My working: $$\ce{...
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1answer
2k views

Calculating n factor of SO2

I'm having a hard time trying to figure out n factor of $\ce{SO2}$ in the reaction $$\ce{FeS2 + O2 → Fe2O3 + SO2}\qquad \text{(unbalanced)}$$ To balance it, I saw that in 1 mole of $\ce{FeS2}$, it ...
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1answer
767 views

Brackets in chemical formulas

When you have brackets such as $\ce{Zn(NO3)2}$, if there is a coefficient around the formula such as $\ce{2Zn(NO3)2}$, how would you read this? Would there be 2 zinc atoms, 4 nitrogen and 12 oxygen ...
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0answers
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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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1answer
4k views

Attempting to balance a redox reaction using half reactions leaves an unbalanced component

I have this redox reaction that I can't balance using half reaction method. $$\ce{Mg + HNO3 -> Mg(NO3)2 + N2O + H2O}$$ What I get at the end is $$\ce{2Mg + 6HNO3 -> 2Mg(NO3)2 + 3N2O +3H2O}$$...
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1answer
5k views

Help balancing reaction between Iron (II) chloride and potassium phosphate

Very rusty with chemistry and looking to review some basics. Came across the following: Iron(II) chloride and potassium phosphate react. Write and balance the molecular, ionic, and net ionic ...
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2answers
747 views

How to calculate the amount of substances product produces from the masses and amounts of starting materials?

Calculate the amount of carbon dioxide formed when we burn 1 mole of carbon in the presence of 16 g of dioxygen. $$\ce{C + O2 -> CO2}$$ 1 mole of carbon means 12 g. Therefore amount of ...
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1answer
176 views

Why not to consider hydrogen and oxygen moles to determine an empirical formula

A question says: Find the empirical formula of an organic compound from the following composition: 34.62% C, 3.88% H, 61.50% O. The answer is $\ce{C3H4O4}$. It was found by using the mass (...
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1answer
14k views

Calculate water hardness from grams of CaCO3

We have to figure out what the water hardness in mg/L or ppm is for a $\pu{20ml}$ solution of $\pu{0.400M}$ $\ce{CaCl2}$. We learned that the formula for hardness is mg/L of calcium carbonate per ...
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6answers
4k views

Why convert to moles for stoichiometry calculations? [closed]

Why do you have to convert the reactants and products of an equation to moles when doing stoichiometry problems? Why can't you just convert straight to grams to solve the problem?