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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Why must chemical equations be balanced? [closed]

I said, "A chemical equation needs to be balanced to obey the law of conservation of mass." Let me come to the point, Why does an equation need to be balanced? What's the reason behind the ...
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How is 1 mole hypochlorite ion equivalent to 1 mole chlorine gas?

According to my book, 1 mole ClO- is equivalent to 1 mole Cl2. How is that even possible? 1 mole ClO- contains 1 mole Cl atoms. On the contrary, 1 mole Cl2 gas contains 2 mole Cl atoms. So, how are ...
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1 answer
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Should I write formula for oxalate or oxalic acid while balancing a redox reaction using the ion-electron method?

Problem: Balance the following reaction using the ion-electron method: $$\ce{H2C2O4 + KMnO4 + H2SO4 -> CO2 + MnSO4 + K2SO4 + H2O}$$ My book's solution: Oxidation half-reaction: $$\ce{C2O4^2- -> ...
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1 answer
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Why did my book write S2- if hydrogen sulfide isn't ionic?

Problem: Balance the following reaction using the ion-electron method: $$\ce{KMnO4 + H2SO4 + H2S -> MnSO4 + S + K2SO4 +H2O}$$ My book's solution: Oxidation half-reaction: $$\ce{S^{2-}->S + 2e^{-}...
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1 answer
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Convention for writing concentration units

1st part of my question: Q) The concentration of an NaCl solution is 1M. Express this in percent wt. by vol. unit. Ans: $$\text{In %(w/v) unit}=\frac{58.5\pu g}{1000\pu{mL}}\times \frac{100}{100}=5.85\...
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1 answer
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What will happen if the electrolysis of Brine takes place for a long time?

This is the reaction: $$\ce{2NaCl(aq) + 2H2O(l) -> 2NaOH(aq) + H2(g) + Cl2(g)}$$ If the above reaction goes on for long enough, we will eventually run out of Cl- ions. There will only remain an ...
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1 answer
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Balanced reaction to Cr given H+ [closed]

The troublesome nature of this post, is that I was given very little information to work with: "The metal chromium (Cr) reacts with an acid, to create Cr^+3 ions, and hydrogen gas. Show the ...
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How much Calcium Hydroxide to manufacture calcium formate?

First, I have no experience with stoichiometry. I currently manufacture calcium formate for a specific use because here in my country, it is very difficult to get calcium formate in small quantities. ...
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Creating sodium tetraborate decahydrate from boric acid

I would like to obtain sodium tetraborate decahydrate (borax) from boric acid (note not the other way around that is answered here: Creating Boric Acid from Borax and Hydrochloric Acid) Perhaps use ...
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Atomic formula obtained by mixing given percentages of oxides

Calculate the atomic formula of a compound which is made by $93\,\%$ of $\ce{SnO2}$ and $7\,\%$ of $\ce{Sb2O5}$. The molar mass of $\ce{SnO2}$ is $\pu{150.71 g mol^-1}$ and the molar mass of $\ce{...
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When balancing equations, how do we handle chemicals in different states of matter?

Balancing chemical equations such as $$\mathrm{H_2 + O_2 \to H_2O}$$ or $$\mathrm{NaHCO_3 + H_3C_6H_5O_7 \to Na_3C_6H_5O_7 + H_2O + CO_2}$$ seems to be easy enough by finding the coefficients of each ...
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2 answers
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What does n(Na2CO3) mean?

In my book, $n(\ce{Na2CO3})$ was used to indicate the number of moles of $\ce{Na2CO3}$ without any clarification. Is it common knowledge among chemists that $n(\ce{Na2CO3})$ indicates the number of ...
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1 answer
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How to correctly use the avogadro number? [closed]

Avogadro constant, $N_A$ is equal to $\frac{6.02214076 \cdot 10^{23}}{mol}$. There is no unit of particle or anything in $N_A$ (nothing like $N_A = \frac{6.02214076 \cdot 10^{23} \ce {particles}}{mol}$...
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3 answers
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How can one determine if a chemical reaction is impossible to balance?

I asked this question on Math Stackexchange, but thought I'd get a more chemical view: https://math.stackexchange.com/questions/4326904/determining-whether-or-not-a-system-of-equations-has-nonzero-...
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1 answer
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Using the mole ratio to figure out the molecular formula [closed]

It takes $\pu{8.0 cm^3}$ of aqueous sodium phosphate to fully react with $\pu{12.0 cm^3}$ of an aqueous solution of the nitrate of metal $\ce{T}$. If both solutions have a concentration of $\pu{1 mol ...
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How is formula for mean ionic activity derived from its constituent activities?

I spent hours in order to understand the following - but without success: At many places the mean ionic activity coefficient for the reaction $$\ldots \rightarrow \nu_A A^{z_A+} + \nu_B B^{z_B-}$$ ...
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Novalucol back titration lab calculations

I had a lab today where we had the goal of figuring out how many moles of HCl were neutralized by one tablet of Novalucol. Novalucol is an antacid tablet containing magnesium hydroxide and calcium ...
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2 answers
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What is the correct molecular, total ionic, and net ionic reaction equation of reaction between magnesium nitrate and sodium chromate? [closed]

From the question, I think that the reactants are $$\ce{Mg(NO3)2(aq) + Na2CrO4(aq)}$$ But the problem is, I am confused about the result of the reaction. Is it $$\ce{MgCrO4}$$ and/or $$\ce{NaNO3}$$? ...
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1 answer
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Confusion with when is asking about impure mass of the component and pure mass [closed]

I've had this problem just to illustrate my confusion better: An impure mixture of $Fe_2O_3$ that reacts with commercial $HCl$ with a density of $1.19 g/mL$, that contains a 35% of mass of the pure ...
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-2 votes
1 answer
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stoichiometric crystal

I wonder if there is something like a "stoichiometric crystal"? In other words: Is it possible to have a crystal that is non-stoichiometric? I'm not interested in crystal defects but don't ...
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Why does/doesn't sodium carbide exist?

(Here, I quote a question from an Indonesian undergraduate Chemistry competition: "sodium carbide reacts with water to form ethyne gas." This is the problem that caused me to ask this ...
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Why we are dividing rate of reaction with respect to a species by its stoichiometry coefficient to find rate of that particular reaction

If there is a reaction like this $$\ce{ H2 + Cl2 -> 2HCl}$$ I can understand that each individual species (reactant or product) can have different rates and we can compare them like this, $$-\frac{...
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Aqueous glucose solution concentration computation

The question in my worksheet is as follows: You dissolve $\pu{1.451 mol}$ of glucose in water to a volume of $\pu{250 mL}$. The mass of the glucose is $\pu{261 g}$ and the molecular weight $\pu{180....
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2 answers
59 views

Looking for volume [closed]

The question in my assignment is as follows. You have 5.5 M $\ce{NaOH}$. The volume of $\ce{NaOH}$ is 0.5 L. How many mL of the 5.5 M $\ce{NaOH}$ solution do you need if you would like to make 300 mL ...
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1 answer
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Need good aproximation to the atomic composition of late 1980's expanded polystyrene foam

I'm not a chemist and what little I know about expanded polystyrene (EPS) foam has been found by looking at articles on the internet. At work I need an approximation to the atomic composition (at %) ...
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2 answers
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How much Na2O (from NaOH) do I add to sodium silicate with a weight ratio of SiO2/Na2O = 2.34 to get the solution to a weight ratio SiO2/Na2O = 1.9?

There is some confusion in industry as sodium silicate is made with NaOH but given a ratio with respect to Na2O (i.e. SiO2/Na2O not SiO2/NaOH). I presume it follows from this equation: 2NaOH -> ...
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1 answer
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Sodium acetate stoichiometry from baking soda and vinegar

I want to make sodium acetate from sodium bicarbonate and vinegar. I'm a bit stumped at calculating amounts of each reagent. I'm starting with 8% acetic acid vinegar. I was going to add, to 1 L of the ...
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1 answer
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NaOH + atmospheric CO2: Unexpected results troubleshooting

I've conducted an experiment where a solution of $\pu{4.2 M}$ $\ce{NaOH}$ was left exposed to atmospheric $\ce{CO2}$ for a period of time and titrated using potentiometric titration and potassium ...
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1 vote
0 answers
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Regarding the reaction of xenon with fluorine gas

In my textbook, under the topic about xenon-fluorine compounds, the following three equations are mentioned: $\ce{Xe(g) + F_2(g) -> XeF2(s)}$ (Xenon in excess / 2:1 ratio) $\ce{Xe(g) + 2F_2(g) -&...
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1 answer
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How is the equilibrium constant for the water-gas shift reaction calculated after it is disturbed?

Consider the following equilibrium process at $\pu{686 ^\circ C}$: $$\ce{CO2(g) + H2(g) <=> CO(g) + H2O(g)}$$ The equilibrium concentrations of the reacting species are $[\ce{CO}] = \pu{0.050 M}$...
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-1 votes
2 answers
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Balancing octane combustion reaction for internal combustion engine

I am trying to balance out the equation for combustion of octane in $120\,\%$ of excess air with products $\ce{CO2},$ $\ce{H2O},$ $\ce{N2},$ and $\ce{O2}$: $$\ce{C8H18 + 1.2$a$(O2 + 3.76 N2) -> $b$ ...
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Calculating molecular formulas of a combustion reaction

The Question In an experiment, 10 cm$^3$ of an organic compound in the gaseous state was sparked with an excess of oxygen. 20 cm$^3$ of carbon dioxide and 5 cm$^3$ of nitrogen were obtained among the ...
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4 votes
1 answer
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What is the n-factor for reduction of chromate(VI) to chromium?

Here a reaction is given: $$\ce{CrO4^2- -> Cr}$$ I don't know the full reaction, but I made some estimates. One estimate was that on balancing charges we get two electrons on right-hand side. I ...
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1 vote
1 answer
867 views

The definition of n-factor, what was it when it was introduced?

I realize that n-factor is an outdated concept however I am interested in its formal definition when it was introduced. We have many definitions now on how to calculate n-factor depending on the type ...
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1 vote
0 answers
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Calculating the molecular mass of an element using relative molecular mass in several compounds [closed]

The relative molecular masses of A, B, and C were found to be $101.30$, $87.30$ and $144.90$ respectively, compared to an assigned value of exactly $2.00$ for $\ce{H2}$. Subsequently, these substances ...
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2 votes
1 answer
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How to balance the reaction equation between copper (I) sulfide and nitric acid?

What is the sum of stoichiometric coefficients of redox reaction: $\ce{Cu2S + HNO3 -> S + NO2 + Cu(NO3)2 + H2O}$? This exercise is from a multiple choice exam. I have balanced the equation: $$\ce{...
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2 votes
0 answers
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What products are formed when KMnO4 and KI react with each other in "weakly basic" medium?

While solving JEE Advanced 2020 (Paper 2) questions, I came across this particular question: According to the final answer key, its answer is 6. In my chemistry book (NCERT Chemistry), the following ...
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1 answer
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Ratio of carbon monoxide and carbon dioxide when carbon and oxygen are made to react [duplicate]

$\pu{12 g}$ of $\ce{C}$ reacts with $\pu{64 g}$ of $\ce{O2}$ to give a mixture of $\ce{CO}$ and $\ce{CO2}$. Find amount of $\ce{CO}$ and $\ce{CO2}$ at the end of reaction. What I tried was to let x ...
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6 votes
2 answers
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Balancing reaction between copper and nitric acid given the ratio of formed nitrogen oxides

Problem $\ce{Cu}$ reacts with $\ce{HNO3}$ according to the equation $$\ce{Cu + HNO3 -> Cu(NO3)2 + NO + NO2 + H2O}$$ If $\ce{NO}$ and $\ce{NO2}$ are formed in 2:3 ratio, what is coefficient of $\ce{...
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1 answer
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Adjusting redox reactions

$$\ce{KCl + KMnO4 + H2SO4 -> K2SO4 + MnSO4 + H2O + Cl2}$$ Attempt. I want to adjust this redox reaction, I've figured out that Chlorine and Manganese are the 2 elements that change thier oxidation ...
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1 vote
0 answers
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Calculate concentrations of ions after acid-base reaction given volumes and concentrations

A $\pu{35.0 mL}$ of $\pu{4000 ppm}$ $\ce{HCl}$ solution is mixed with $\pu{45.0 mL}$ of $\pu{0.1025M}$ $\ce{NaOH}$ solution. Assume volumes are additive. $$\ce{NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(...
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1 answer
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Calculating atomic mass of unknown element in given compound (gas) at STP

A gas $\ce{X2O5}$ has the density of $\pu{5 g L-1}$ at STP. What is the atomic mass of $\ce{X}$ given $A_\mathrm{r}(\ce{O}) = 16?$ Note: The problem is my homework for school and has been translated ...
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1 vote
1 answer
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Finding formula of reduced scandium oxide using its mass and mass of obtained metal

An oxide of scandium, with a mass of $\pu{1.423 g},$ is chemically reduced with $\ce{H2}$ to give $\ce{H2O}$ and $\pu{0.929 g}$ of $\ce{Sc}$ metal. What is the formula of scandium oxide? How much ...
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1 vote
1 answer
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Reaction stoichiometry for calculation of Kp

NH$_2$CO$_2$NH$_4$(s)⇌$2$ NH$_3$(g)+ CO$_2$(g) I want to calculate K$_p$ for the reaction above, given that the total pressure is $0.63$ bar. My calculations: $0.63$ = p(CO$_2$) + p(NH$_3$) , where ...
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10 votes
7 answers
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What is the mathematical meaning of the plus sign (+) in chemical reaction equations?

Reactants and products are connected with plus signs in a chemical reaction equation, e.g. $$\ce{CH4 + 2 O2 -> CO2 + 2 H2O}.$$ Is there a strict mathematical interpretation of what looks like sums ...
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1 vote
0 answers
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How to calculate non-stoichiometric ratio [closed]

I'm reading a paper "Photocatalysis-mediated drug-free sustainable cancer therapy using nanocatalyst." Here, the authors synthetise nanoplates of $\ce{SnS_{1.68}}$ with nanodots of $\ce{WO_{...
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1 vote
1 answer
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Using PV = nRT to solve an electrolysis problem

Question: Two electrolytic cells are connected in series (the same current passes through each cell). One cell for the electrolysis of water produces $\pu{100 cm^3}$ of oxygen, measured at $\pu{273 K}$...
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-2 votes
1 answer
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Why do we only take into account the first product while calculating a limiting reactant?

High school chemistry student here. Currently, we are learning stoichiometry and I noticed that when we calculate the limiting reactant of a reaction with multiple products, we almost always just take ...
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2 answers
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Writing a chemical equation with a reactant of unspecified chain length [closed]

Would appreciate it if I got some general tips and hints and not the solution cause I'm trying to learn from this question :) The question is as follows: FA1 is a solution containing $\pu{5.00 g dm-3}...
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0 votes
1 answer
131 views

Converting w/v to mole fraction

If I have 10 mL 0.9% w/v $\ce{NaCl}$ solution, I can deduce that the solution contains 0.09 g of $\ce{NaCl}$. Imagine that this is standard laboratory conditions and 1 ml = 1 g is acceptable. Is the ...
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