# 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-word measurements to atomic scale phenomena.

194 questions
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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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### 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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### 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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### 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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### 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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### How to calculate the mass of a single atom?

If we know the molar mass of a certain element and Avogadro's constant, how can we calculate the mass of a single atom? Do we need to multiply the molar mass with 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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### 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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### 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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### 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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### 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 ...