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Questions tagged [mole]

The mole is a standard amount of a substance A mole of a substance is a number of units (particles, atoms, molecules, ions, peas, hard candies, people, universes) equal to the number of atoms of carbon-12 in one gram of carbon-12, or an Avogadro's number of stuff. The mole allows us to relate real-...

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Why are osmoles not considered SI units?

The Wikipedia article for osmoles is pretty clear on what they are and how they are used. Right off the bat, though, it states that the osmole is not an SI unit, and indeed the usual lists of derived ...
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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?
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How to determine the equation for the reaction of europium with sulfuric acid based on experimental measurements?

I was given a set of results by a fellow researcher where he reacted $0.608~\mathrm{g}$ of europium ($M = 152$) with an excess of $\ce{H2SO4}$ and collected $144~\mathrm{cm^3}$ of $\ce{H2}$ gas at ...
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Volume of one equivalent of a gas

How do we define an equivalent when we are not talking about any particular reaction? Like, we say that equivalent volume of Oxygen is 5.6L, so we have taken the n-factor to be 4, and in CO2 we take n-...
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167 views

Calculating molar mass from gas data

34.05 mL of phosphorus vapour weighs 0.0625 g at 546 °C and 0.1 bar pressure. What is the molar mass of phosphorus? I tried to solve the above question and got 1249.8g. The book's answer sheet lists ...
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How many mL of 10.00 M HCl are needed to make up 80.0 mL of 0.175 M HCl?

I've tried this multiple times, but I don't know how to set the problem up when it gives you both molarities. If someone could show me how to set up this problem please!? I think it has something to ...
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1answer
145 views

Find the amount of atoms for a given mass

The atomic mass of two elements A and B is 40 and 80 respectively. If x g of A contains y atoms, how many atoms are present in 2x g of B? I have tried to solve by assuming that x g of A has y atoms ...
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How to calculate n factor for redox reactions? [duplicate]

Books generally don't go deep into this concept but i need to know,how to calculate the n factor for various types of redox reactions like oxidation number of one element changes and goes into 2 ...
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Why do we assume that it is 1 mol?

A question in my book was as following: Benzine and chloroform are considered very toxic organic solvents that dissolve in each other and in a solution of benzine and chloroform there is 0.45 mol ...
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1answer
88 views

Number of water molecules to contribute one molecule to every milliliter on earth

How many millilitres of water would it take so that, when they are thoroughly dispersed around the world, it would yield an average of one molecule of the original sample of water in each millilitre ...
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699 views

Raoult's Law and Mole Fraction

Raoult's Law states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture....
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Calculating the mass of a single atom

If we know the molar mass of a certain element and the Avogadro's constant, how can we calculate the mass of a single atom? Do we need to multiply the molar mass value and Avogadro's constant?
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How to calculate the maximum number of molecules or ions from a given amount of substance?

Which of the following solutions has the greatest number of particles (atoms or ions) of solute per liter? (a) $1~\mathrm{M}\ \ce{NaCl}$ (b) $1~\mathrm{M}\ \ce{CaCl2}$ (c) $1~\mathrm{M}$ ...
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Calculate the heat of a reaction

Say I would like to calculate the heat produced by the following reaction: $$\ce{2SO2 + O2\longrightarrow2SO3}$$ I have calculated the moles of the reagents. I can't seem to figure out how to ...
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463 views

How to calculate a molar mass based on density?

I have been asked to calculate the molar mass and mole fraction of a 35 w/w% HClO4 solution with a density of 1.3g per ml. This is the equation I used to try to solve it: $\frac{1}{M} = \frac{0.35}{...
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423 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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Determining water of crystallisation in a hydrate from the mass percentages

How would I find the amount of water in a hydrate if all I was given was the mass percentage of one element in the compound? For example, a question asks: $\ce{Zn(ClO3)2. $x$H2O}$ contains $21.5\%$ ...
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Ratios and mass; reaction calculation problem

I have come across the following problem: One method used to inflate air bags in cars is to use nitrogen produced chemically from the decomposition of sodium azide. The sodium formed reacts with ...
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What's the empirical formula of this solid? Reacting mass calculation

I have come across the following problem: $1.00\ \mathrm g$ of sulphur dissolved completely in an excess of liquid ammonia to give $420\ \mathrm{cm^3}$ of hydrogen sulphide ($\ce{H2S}$), measured ...
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1answer
291 views

pH of a mixture of base and an acid

I have the following question: Assume that you have two solutions. One of $50\ \mathrm{cm^3}$ $\ce{HCl}$ $\mathrm{pH} = 1.3$ and one of $150\ \mathrm{cm^3}$ $\ce{Ba(OH)2}$ $\mathrm{pH} = 12.3$. If we ...
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How many grams of sodium sulfate and water in 100ml of 0.5M solution

Calculate how many grams of sodium sulfate ($\ce{Na2SO4}$) and water ($\ce{H2O}$) should be used to prepare $\pu{370 g}$ of 15% solution of this salt. How many mL of this 15% solution should be taken ...
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Can chemicals be identified by their molar mass?

Wouldn't it be possible to identify a chemical by measuring its molar mass? How much accuracy does the measured molar mass need to be to guess what chemical it could be? EDIT: @ortho makes an ...
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76k views

How to Find the Mass of an Individual Element in a Compound/Molecule [closed]

What is the procedure/math for finding the mass of a specific element in a substance? For instance, how many grams of Oxygen are in 6.8 grams of Epinephrine (Adrenaline)?
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Can anyone give me detailed logical solution to my questions? [closed]

What is 1 amu? From where it is derived? Why it is compared with carbon-12? Why it was once compared with hydrogen-1? and now its not? Can anyone please explain me logically? And what would have ...
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How is the mol highway used in this problem?

How many moles of propane gas, $\ce{C3H8}$, are contained in 11 grams of the gas at standard conditions? Also, can you please explain step-by-step (and include sigfigs?) I think I might know how to ...
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1answer
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How to find the number of hydrogen atoms in 0.5 mol of hydrogen gas?

How do I calculate the number of hydrogen atoms in $\pu{0.5 mol}$ of hydrogen gas? I presume the answer would probably somehow use the equation $$n = \frac{m}{M},$$ where $n$ is the amount of ...
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1answer
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Molarity of Sodium Ion Concentration (and some really weird answers…)

I know how to do this problem really easily but I don't know why my answer is wrong... The problem is: What is the molarity of sodium ions in a solution prepared by diluting $250\ \text{mL}$ of $0....
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1answer
6k views

How do I calculate the cost of a single Aluminum atom?

I am doing a Chemistry assignment in which I was given a piece of aluminum foil which I had to measure and use for my calculations. I am supposed to calculate the cost of a single aluminum atom using ...
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1answer
632 views

Why is the amount in a mole equal to the Avogadro's number?

This question just popped in my head as I was working with electric force problems involving atoms. Why is the amount in a mole equal to the Avogadro's number? Do atoms/molecules/etc. tend to group in ...
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What advantages does the mole have over counting large numbers using SI prefixes?

I'm trying to understand why chemists use the mole unit instead of just counting and using SI prfixes to simplify the big numbers with units such as zetta- or yotta-molecules (yotta=10^24). Here's ...
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1answer
238 views

At what point does Avogadro's law not apply?

A mole of hydrogen gas takes up 22.4 L, but so does a larger molecule like $\ce{CO2}$. Methane ($\ce{CH4}$) is an even larger sized molecule, but a mole of it will still take up 22.4 L. I would assume ...
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How to find the amount of moles given mass percentage data

A hydrated aluminium sulphate, $\ce{Al2(SO4)3.xH2O}$, contains 8.10% of aluminium by mass. Find the value of x. My attempt: (Assuming 100g sample) Calculate the amount of aluminium using the formula ...
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Why are the mass ratios of O to KClO3 and O2 to KClO3 the same?

I just did a lab that involved heating KClO3 (with MnO2 as a catalyst) to decompose it into KCl and oxygen gas. That part is easy. What's throwing me is the % yield calculations. The theoretical ...
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Why not an Avogadro's principle for solid matter?

Avogadro stated that for any ideal gas, 1 mole of particles will occupy a specific volume at a specific ratio of pressure and temperature. So why doesn't this apply to a liquid or solid?
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Does 11.2 dm3 of nitrogen consist of 0.5 moles at STP?

Which of the following statements is true? $11.2~\mathrm{dm^{3}}$ of nitrogen at STP A: has a mass of $14\ \mathrm{g}$. B: consists of $0.5\ \mathrm{mol}$ atoms. My instinct was that the answer is ...
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Comparing heat of hydrogenation per mole of butenes and 1,3-butadiene

The question asks us to select the compound with the smallest heat of hydrogenation per mole out of the following: a) 1-butene b) trans-2-butene c) cis-2-butene d) 1,3-butadiene Since all four ...
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What is the correct value of the Avogadro constant? And how was it derived?

I found different values of Avogadro constant in different places. So what is the correct value? $\pu{6.0221367*10^{23}}$ or $\pu{6.02214129*10^{23}}$ or $\pu{6.0221415*10^{23}}$ or anything else?
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CuCl2 dissolved in water

We dissolve $10\ \mathrm{g}$ of $\ce{CuCl2}$ in $0.1\ \mathrm{L}$ of water. Given that: $M(\ce{Cl})=35.5\ \mathrm{g/mol}$ $M(\ce{Cu})=63.5\ \mathrm{g/mol}$ How can one calculate the molar ...
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1answer
1k views

Solute mole fraction for hydrated magnesium sulfate dissolved in water

Problem: 70 grams of pure, hydrated $\ce{MgSO_4}$ is dissolved in 90 grams of $\ce{H_2O}$. If the mole fraction of the solute is 0.039, find the molecular formula of the solute. My flawed attempt ...
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1answer
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Calculating the number of molecules remaining

This is the question in my text book: From $392\:\mathrm{mg}$ of $\ce{H2SO4}$, $1.204 \times 10^{21}$ molecules are removed. How many moles of $\ce{H2SO4}$ are left? What I tried doing: First I ...
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1answer
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Is the largest number of molecules in 36 g of water or 54 g of dinitrogen pentaoxide?

So recently my teacher asked us which of the following has the largest number of molecules? He gave us two options: 36g of $\ce{H2O}$ 54g of $\ce{N2O5}$ I'm stuck, because both of them are having ...
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1answer
7k views

What is the effect of the temperature on the no of moles in an equilibrium system?

Here's something that makes me confuse. What will happen to the total no of moles in a system if the temp is raised. Will it increase? If so how is that possible.? Say we have an equlibrium, $$\ce{2P &...
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Converting g/L to mol/L

I know I should divide $\mathrm{g~L^{-1}}$ by the molar mass of the substance, but I don't seem to find the specific answer on Google. So just to be sure: If I have $10^{-5}~\mathrm{g~L^{-1}}~\ce{Cu^...
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What is the mass of 1 atom of carbon?

I know that relative atomic mass of $\ce{^{12}C}$ is $12~\mathrm{u}$. Therefore mass of $1~\mathrm{mol}~\ce{C} = 12~\mathrm{g}$ \begin{align} \text{mass of }6.022\cdot 10^{23} \text{ C atoms} &= ...
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Co49Ni21Ga30 - molar mass and density

I need to calculate the molar mass and density of the shape memory alloy $\ce{Co49Ni21Ga30}$ (I suppose the numbers indicate the mass percentage). To get the molar mass, is it correct to use the ...
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How much sulphuric acid can be obtained from 5 kg of sulfur

How much sulfuric acid $(\ce{H2SO4})$ can be obtained from 5 kg of sulfur $\ce{S8}$? answer: 15.312 kg To make 1 molecules of $\ce{H2SO4}$ we need 1 atoms of S. Now coming to $\ce{S8}$. ...
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1answer
7k views

Do I have to consider the molecular mass of the oxygen atom or the diatomic oxygen molecule when determining the empirical formula of an iron oxide?

In determining the empirical formula of a compound which constitutes a diatomic molecule, should we calculate the molar mass of the divalent molecule by multiplying the molar mass of the element by 2, ...
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3k views

How to calculate the osmotic pressure of a sucrose solution?

The boiling point of an aqueous solution containing sucrose, $\ce{C12H22O11}$, is $101.45~^\circ\mathrm{C}$. Calculate the osmotic pressure of this solution at $35~^\circ\mathrm{C}$, at which the ...
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1answer
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How to calculate valence factor (n-factor) for a element?

Suppose I am given some reaction in which $$\ce{C6H12O6 -> CO2}$$ and I want to calculate n-factor for this reaction to ultimately calculate equivalent weight of carbon for this reaction. Since $$...
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2answers
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Determine molecular weight of biomass based on ultimate analysis [duplicate]

The ultimate analysis (by weight percent) for beech wood is: $$\ce{C}=49.05\,\%,\; \ce{H}=5.83\,\%,\; \ce{O}=45\,\%,\; \ce{N}=0.12\,\%$$ Using the ultimate analysis values, the molar mass of each ...