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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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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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0answers
11 views

What is the percent of Fe that exists as Fe3+ in iron oxide Fe0.94O? [on hold]

What is the percent of Fe that exists as Fe3+ in iron oxide Fe0.94O? This is a question in BITSAT sample mock test. I want to know the answer. Can anyone help me?
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0answers
22 views

Mass percentage prblem from chang chemestry book [on hold]

I need help with a exercise from Raymond Chag chemistry book (11th edition): If for each $\ce{N}$ atom from $\ce{C3H5N3O9}$ (Nitroglycerin) forms one $\ce{NO}$ (nitric oxid) what is the percentage ...
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1answer
32 views

Calculating the percentage purity of CaCO$_3$ in a sample of chalk [on hold]

$\pu{1.5 g}$ of chalk were treated with $\pu{10 mL}$ of $\pu{4 N} \; \ce{HCl}$. The chalk was dissolved and the solution made to $\pu{100 mL}$. $\pu{25 mL}$ of this solution required $\pu{18.75mL}$ ...
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1answer
35 views

A question in stiochiometry [closed]

How many moles of $\ce{NH3}$ are there in $\pu{90 L}$ of it at STP? $4$ $32\times 10^{23} $ $23$ $3.2$ Please explain your answer as much as possible.
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0answers
23 views

Calculating Volume of CO2 produced [closed]

The question states "What volume of CO2 will be produced if you react 1.5 g of Li2CO3 with an excess of 6.0 M HCl at room temperature?" Which fundamental equations could be used to solve such a ...
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0answers
22 views

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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0answers
12 views

Calculate the amount of substance in 2.7 gram of aluminium [closed]

Calculate the amount of substance in 2.7 gram of aluminium.
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1answer
31 views

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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1answer
27 views

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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2answers
32 views

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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0answers
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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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2answers
55 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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1answer
52 views

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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1answer
74 views

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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0answers
41 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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2answers
261 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
71 views

Stoichiometry of the redox reaction with crystallohydrate [closed]

Consider the following balanced equation: $\ce{2 Al(s) + 3 CuCl2 . 2 H2O (aq) → 3 Cu (s) + 2 AlCl3 (aq) + 6 H2O (l)}$ If we began the experiment with 0.99 g of Al, according to the ...
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1answer
43 views

Important Stoichiometry question, just need formula or help and answer checking [closed]

How many grams of Cobalt(II) chloride $\ce{CoCl2}$ is needed to make $\pu{0.645 L}$ with a concentration of $\pu{1.25 mol\:L^{-1}}$? (the molar mass of anhydrous $\ce{CoCl2}$ is $\pu{129.839 g\: mol^...
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1answer
72 views

What are the limitations of a waters of hydration experiment? [closed]

When a hydrated salt such as $\ce{CuSO4.5H2O}$ is subjected to heat, an anhydrous salt ($\ce{CuSO4}$) is produced. However the theoretical molar ratio of $\ce{H2O:CuSO4}$ and experimental molar ratio ...
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1answer
46 views

Calculate the empirical formula of the compound containing nitrogen and oxygen [closed]

Calculate the empirical formulas of the compounds containing: nitrogen 47% and oxygen 53%. My guess was to get the molar mass of N and O and divide that by 47 and 53 and continue from there because ...
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3answers
79 views

An aqueous solution of NaCl has a mole fraction of 0.21. What is the mass of NaCl dissolved in 100.0 mL of solution? [closed]

Work mole fraction of NaCl = 0.21/0.21+0.79 If there is 1 mol of total solution, there will be 0.21 mol NaCl and 0.79 mol H2O 0.21 mol NaCl = 12.27 g 0.79 mol H2O = 14.23 g this would yield a ...
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2answers
92 views

How much of Ag has formed on the Cu tile?

$\pu{9.547 g}$ $\ce{Cu}$ tile is added to an $\ce{AgNO3}$ solution. After some time, $\ce{Cu}$ was taken out of the solution, washed, dried and weighed. The mass appeared to be $\pu{9.983 g}$. How ...
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1answer
35 views

Mass fraction in a mixture of metal salts given the total mass of the metal

I am trying to solve a question in my study and I don't get the answer required. A mixture of $\ce{NaNO3}$ and $\ce{Na2SO4}$ weight $5.37$ grams, the $\ce{Na}$ = $1.61$ grams. What is the ...
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2answers
49 views

Determining the formula of zirconium oxide

I am doing the following question (from the 1988 HSC Chemistry paper): In the 19th Century the atomic weight of zirconium (Zr) was known but there was considerable doubt about the formula of ...
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2answers
55 views

Percent hydrogen and carbon [closed]

A 1 g sample of an organic compound was burned in a combustion analyzer and yielded 1.42 g carbon dioxide and 0.872 g of water. Calculate the percent carbon and hydrogen in the sample. From the ...
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2answers
313 views

Finding mole fraction from molality

Calculate the mole fraction of ammonia in a $\pu{2.00 m}$ solution of $\ce{NH3}$ in water. What I know is that the formula for mole fraction is $$X = \frac{\text{no.-of-moles-of-solute}}{\text{(no.-...
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1answer
98 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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1answer
148 views

What exactly is a reducing equivalent and what does it do?

I've encountered this term in the context of cellular metabolism, but I can't seem to find an explanation of what a reducing equivalent is or why it is named this way. Wikipedia was not really helpful,...
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1answer
37 views

Evaluate mass of salt needed to add to a buffer solution knowing only pH

This is an exercise taken from an old exam, I'm struggling with the resolution. To a solution of a generic weak acid $\ce{HA}$ were added $\pu{2.40 g}$ of a potassium salt of the $\ce{KA}$. The ...
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1answer
60 views

Determination of molecular formula of hydrocarbons by combustion analysis

So, I've this question in my textbook: $\pu{20 mL}$ of unknown gaseous hydrocarbon reacts with excess oxygen gas. It decreases by $\pu{30 mL}$ upon cooling down. It decreases farther $\pu{40 mL}$ ...
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1answer
48 views

If the net ionic equation and complete equation balance differently, which one do you use? [closed]

Sometimes the full equation of a reaction and the net ionic equation balance out differently. If that is the case, which is the correct one to use? For instance, in the reaction between a solution of ...
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1answer
36 views

finding out fractions of ions(different valencies/charges) of an element in non-stoichiometric compounds

Analysis shows that nickel oxide has the formula $Ni_{0.98}O_{1.00}$. What fractions of nickel exist as $Ni^{2+} $and $Ni^{3+}$? What i did: Let the number of $Ni^{2+}$ and $Ni^{3+}$ atoms be $x$ ...
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1answer
36 views

How to distinguish between iron and nickel based on the mass of precipitate formed with sodium hydroxide?

For the reactions shown below, we added $\pu{5.00 mL}$ of $\pu{0.0390 M}$ $\ce{NaOH}$ to a test tube containing one of the two cations $\ce{Ni^2+}$ or $\ce{Fe^3+}$ and recovered $\pu{0.00695 g}$ of ...
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1answer
118 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 ...
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1answer
26 views

How do I identify how many reactions are occurring when precipitating a mixture?

An example of a question is: After dissolving $x$ grams of a mixture of $\ce{Na2SO4}$ and $\ce{NaCl}$ in water, you add an excess of $\ce{BaCl2}$ solution. You filter off the precipitate which ...
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2answers
167 views

Calculate the concentration in milimoles per litre (mM) of a solution that is 20% H2SO4 by mass and that has a density of 1.198 g/L

Calculate the concentration in milimoles per litre ($\pu{mM}$) of a solution that is $\pu{20\%} \ce{H2SO4}$ by mass and that has a density of $\pu{1.198 g/L}$. For the answer, please provide two ...
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1answer
143 views

Finding mass percentage of components of a solid mixture

A workbook question asks: $\pu{2.184g}$ of a solid mixture containing only $\ce{K2CO3}$ ($\mathrm{FW = 138.2058}\pu{ g/mol}$) and $\ce{KHCO3}$ ($\mathrm{FW = 100.1154} \pu{g/mol}$) is dissolved in ...
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1answer
152 views

Balancing the reaction of nitric acid with zinc using oxidation number method

In a previous question, there was confusion relating to what this "oxidation number method" is. So I will illustrate that before my question. Write the skeleton equation representing chemical ...
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2answers
544 views

What is the net ionic equation of the following?

Aqueous chlorine is added to a solution of aluminum bromide in a single replacement reaction which forms no precipitate and bromine liquid. Determine the net ionic equation. Since this is a single ...
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3answers
53 views

Copper Stoichometry Ratio Problem

I was given two equations as part of a problem into Copper Wiring production for planes: $$\ce{4CuFeS2 + 9 1/2 O2 + 4SiO2 \rightarrow Cu2S + Cu2O + 2SO2 + 4FeSiO3}$$ $$\ce{Cu2S + 2Cu2O \rightarrow ...
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1answer
68 views

Balancing the intermolecular redox reaction

The redox reaction is: $\ce{SO2 + Na2CrO4 + H2SO4 -> Na2SO4 + Cr2(SO4)3 + H2O}$ This is what I tried(tho I got stuck at one point which is indeed the exact reason why I've asked this question): ...
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2answers
192 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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1answer
208 views

Concentration of excess reactant

If increasing/decreasing the concentration of an excess reactant influenced the percentage yield of a product experimentally, how could this be explained? I know that in theory, the excess shouldn't ...
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1answer
39 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. ...
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1answer
70 views

Stoicheometry questions: I've been having a bad time not understanding the questions and how the steps are to achieve the answer. please help [closed]

Cetyl palmitate (C32H64O2) is a waxy solid and is the main component of spermaceti, the once prized wax found in the skull of sperm wales. The heads of sperm whales can contain up to 1900 L of ...
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1answer
699 views

Stoichiometric amounts

Can anyone inform me what the term stoichiometric amounts means. I know what stoichiometry means. It is the: The relationship between the relative quantities of substance taking part in a reaction ...
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1answer
92 views

Is it possible for me to derive Avogadro's number?

To my understanding the mole is the unit used to translate between mass on the atomic level and mass in the macro level, defined as the number of atoms in $12$ grams of Carbon-$12$, which apparently ...
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1answer
49 views

Finding empirical formula [closed]

When determining the formula of a compound, why do we divide by the smallest number of moles once we already have calculated the number of moles for each element in order to find the empirical formua ...
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1answer
76 views

How did early chemists measure mass of atoms?

Here a book says that Berzelius measured atomic masses using a simple lab and his measurements was so close to modern results. Can someone explain how a person living in 19th century was able to ...