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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-word measurements to atomic scale phenomena.

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Why is the definition of the mole as it is?

I have asked my teacher, as she was introducing the concept of mole to us, why that number was chosen, instead of more convenient one. She told me that it came from the definition of the mole, that is the number of atoms in 12g of Carbon 12. When I…
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Why has the mole been redefined for 2019?

The mole is still defined as an SI unit representing the number of constituent particles (whether they be atoms, molecules etc.) in 12 grams of carbon isotope 12 (carbon-12). Effective from May 20 this year the definition of the mole will change to…
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What exactly is a mole?

Upon coming back to University I've started studying basic chemistry again. I've always had trouble with the concept of "moles". According to my study book, 1 mole of any element or compound is equal to its molecular weight in grams. I…
teachmechemistry
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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 what I've found so far, but it doesn't seem to be…
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Why is weight of 1 mole of substance equal to atomic/molecular mass in grams?

Why is weight of 1 mole of substance equal to atomic/molecular mass in grams? According to me, it happens because mole has been defined in such a way. It is defined as the numbers of particles in $\pu{12 g}$ of $\ce{^{12}C}$. If it were $\pu{24…
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Why is the mole a unit of measurement?

I really can't understand why is the mole a unit of measurement and not just a constant. I mean, we use units to express things that we can measure but that are not countable, that are continuous - and not discrete. However, the number of atoms (or…
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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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Atomic mass unit based on other atoms

Question: Which one is larger: an atomic mass unit based on the current standard or one based on the mass of a Be-9 atom? My attempt: Current standard is $1/12$th the mass of a C-12 atom. New standard is $1/9$th the mass of a Be-9 atom. Now I…
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amu and g/mol relation

Do we have that $\pu{1 g/mol} = \pu{1 amu}$ ? Because we have, for the mass of an atom of carbon 12, call it $m(\ce{^12C})$, that $$m(\ce{^12C}) = \pu{12 amu}$$ and furthermore $$\pu{1 mol} \cdot m(\ce{^12C}) = \pu{12 g}$$ therefore $$m(\ce{^12C}) =…
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Why is molality per mass solvent rather than per mass of solution?

Knowing the moles of substance per mass of solution would be useful. Pour some solution and you'd know how much substance you have. Why is molality defined not this way, but as moles of substance per mass solute instead? It seems like this unit was…
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Is Avogadro's number an integer?

I have heard that Avogadro's number, $N_\mathrm A=6.022 \times 10^{23}$, is the number of atoms contained in $12$ grams of $\ce{^{12}C}$. I think it should be an integer, but I couldn't find the exact number. Is it an integer?
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Avogadro's Number: 6.023 x 10^23 or 6.022 x 10^23?

I was taught that Avogadro's number was $6.023 \cdot 10^{23}$. Now, the accepted value is allegedly $6.022 \cdot 10^{23}$. Has there been a change? If so, when and why? There are still some sites that use $6.023 \cdot 10^{23}$, so if this is wrong,…
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What is the standard molar weight of Carbon, and why?

The mole is defined as the amount of a chemical substance which contains as many representative particles, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of carbon-12 (12C), the isotope of carbon with relative…
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How to define equivalents here

$3g$ of activated charcial was added to $50 ml$ of acetic acid solution ($0.06N$) and filtred after an hour and it was found to be $0.042 N$ .The amount of acetic acid adsorbed (per gram of charcoal) is The solution for this question is exactly…
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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 this exact amount? Why do we use this number as…
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