Why has the mole been redefined for 2019?Effects of Changing Avogadro's ConstantWhy is the mole a unit of...
Can a hotel cancel a confirmed reservation?
Why has the mole been redefined for 2019?
Dilemma of explaining to interviewer that he is the reason for declining second interview
What are "industrial chops"?
Why publish a research paper when a blog post or a lecture slide can have more citation count than a journal paper?
What is the wife of a henpecked husband called?
Why is Agricola named as such?
My cat mixes up floors. How can I help him?
Why was Lupin comfortable with saying Voldemort's name?
Publishing research using outdated methods
What is 6÷2×(1+2) =?
Finding a mistake using Mayer-Vietoris
Simple text-based tic-tac-toe
When can a QA tester start his job?
How much mayhem could I cause as a sentient fish?
Intern applicant asking for compensation equivalent to that of permanent employee
Can we use the stored gravitational potential energy of a building to produce power?
How do you funnel food off a cutting board?
Which one of these password policies are more secure?
Why did Luke use his left hand to shoot?
初めてです, is '初めて' an adverb?
One Half of Ten; A Riddle
Why avoid shared user accounts?
In Linux what happens if 1000 files in a directory are moved to another location while another 300 files were added to the source directory?
Why has the mole been redefined for 2019?
Effects of Changing Avogadro's ConstantWhy is the mole a unit of measurement?What advantages does the mole have over counting large numbers using SI prefixes?Is this definition of mole correct?Effects of Changing Avogadro's ConstantHow to correctly write “7 apples” according to the international system of units (SI)What is a mole?What is the standard molar weight of Carbon, and why?Alternative definition of the mole?How are the molar mass and molecular mass of any compound numerically the same?Effect of redefining Avogadro's constant and kilogram on molar mass
$begingroup$
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 a unit representing Avogadro constant number of particles.
Since the Avogadro constant was and will be still tied to the mole (number of particles in a mole), I think this also changed the definition of the Avogadro constant, though I'm not sure. Although the old and new definitions define the constant as the number of particles contained in the mole, it seems that the definition of the mole has changed from the earlier carbon-12 definition to simply the Avogadro constant.
First of all I would like to know if anyone knows why this redefinition happened now (it was decided at the end of the last year).
Also, please correct anything wrong I've said. This is rather confusing for me and the definitions seems rather circular. The new definitions are that Avogadro's constant is the amount of particles in a mole, and a mole is defined by the Avogadro constant.
Previous definition:
The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
2019 definition:
The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
Avogadro constant - Wikipedia
mole
New contributor
$endgroup$
add a comment |
$begingroup$
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 a unit representing Avogadro constant number of particles.
Since the Avogadro constant was and will be still tied to the mole (number of particles in a mole), I think this also changed the definition of the Avogadro constant, though I'm not sure. Although the old and new definitions define the constant as the number of particles contained in the mole, it seems that the definition of the mole has changed from the earlier carbon-12 definition to simply the Avogadro constant.
First of all I would like to know if anyone knows why this redefinition happened now (it was decided at the end of the last year).
Also, please correct anything wrong I've said. This is rather confusing for me and the definitions seems rather circular. The new definitions are that Avogadro's constant is the amount of particles in a mole, and a mole is defined by the Avogadro constant.
Previous definition:
The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
2019 definition:
The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
Avogadro constant - Wikipedia
mole
New contributor
$endgroup$
1
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago
add a comment |
$begingroup$
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 a unit representing Avogadro constant number of particles.
Since the Avogadro constant was and will be still tied to the mole (number of particles in a mole), I think this also changed the definition of the Avogadro constant, though I'm not sure. Although the old and new definitions define the constant as the number of particles contained in the mole, it seems that the definition of the mole has changed from the earlier carbon-12 definition to simply the Avogadro constant.
First of all I would like to know if anyone knows why this redefinition happened now (it was decided at the end of the last year).
Also, please correct anything wrong I've said. This is rather confusing for me and the definitions seems rather circular. The new definitions are that Avogadro's constant is the amount of particles in a mole, and a mole is defined by the Avogadro constant.
Previous definition:
The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
2019 definition:
The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
Avogadro constant - Wikipedia
mole
New contributor
$endgroup$
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 a unit representing Avogadro constant number of particles.
Since the Avogadro constant was and will be still tied to the mole (number of particles in a mole), I think this also changed the definition of the Avogadro constant, though I'm not sure. Although the old and new definitions define the constant as the number of particles contained in the mole, it seems that the definition of the mole has changed from the earlier carbon-12 definition to simply the Avogadro constant.
First of all I would like to know if anyone knows why this redefinition happened now (it was decided at the end of the last year).
Also, please correct anything wrong I've said. This is rather confusing for me and the definitions seems rather circular. The new definitions are that Avogadro's constant is the amount of particles in a mole, and a mole is defined by the Avogadro constant.
Previous definition:
The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
2019 definition:
The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.02214076 × 1023 elementary entities. This number is the fixed numerical value of the Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
Avogadro constant - Wikipedia
mole
mole
New contributor
New contributor
New contributor
asked 3 hours ago
ZebrafishZebrafish
1212
1212
New contributor
New contributor
1
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago
add a comment |
1
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago
1
1
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
You have already mentioned the last definition of the mole before the proposed change:
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.
(…)
According to this definition, the mole still depends on the definition of the kilogram. The main purpose of the proposed change is to find an independent definition. Another purpose is the possibility of linking the definition to an exact value (similar to the speed of light.)
The formal decision for the change was made during the 26th meeting (13–16 November 2018) of the General Conference on Weights and Measures (CGPM).
The motivation behind the change of the definition of the mole can, for example, be found in the resolutions of the 24th meeting (17–21 October 2011) of the General Conference on Weights and Measures (CGPM); however, the discussions and preparations started already much earlier.
On the possible future revision of the International System of Units, the SI
(…)
considering
(…)
that of the seven base units of the SI, only the kilogram is still defined in terms of a material artefact, namely, the international prototype of the kilogram (1st meeting of the CGPM, 1889, 3rd meeting of the CGPM, 1901), and that the definitions of the ampere, mole and candela depend on the kilogram,
(…)
that it is also possible to redefine the mole so that it is linked to an exact numerical value of the Avogadro constant $N_mathrm A$, and is thus no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of $h$, thereby emphasizing the distinction between amount of substance and mass,
(…)
$endgroup$
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "431"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Zebrafish is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fchemistry.stackexchange.com%2fquestions%2f110189%2fwhy-has-the-mole-been-redefined-for-2019%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
You have already mentioned the last definition of the mole before the proposed change:
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.
(…)
According to this definition, the mole still depends on the definition of the kilogram. The main purpose of the proposed change is to find an independent definition. Another purpose is the possibility of linking the definition to an exact value (similar to the speed of light.)
The formal decision for the change was made during the 26th meeting (13–16 November 2018) of the General Conference on Weights and Measures (CGPM).
The motivation behind the change of the definition of the mole can, for example, be found in the resolutions of the 24th meeting (17–21 October 2011) of the General Conference on Weights and Measures (CGPM); however, the discussions and preparations started already much earlier.
On the possible future revision of the International System of Units, the SI
(…)
considering
(…)
that of the seven base units of the SI, only the kilogram is still defined in terms of a material artefact, namely, the international prototype of the kilogram (1st meeting of the CGPM, 1889, 3rd meeting of the CGPM, 1901), and that the definitions of the ampere, mole and candela depend on the kilogram,
(…)
that it is also possible to redefine the mole so that it is linked to an exact numerical value of the Avogadro constant $N_mathrm A$, and is thus no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of $h$, thereby emphasizing the distinction between amount of substance and mass,
(…)
$endgroup$
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
add a comment |
$begingroup$
You have already mentioned the last definition of the mole before the proposed change:
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.
(…)
According to this definition, the mole still depends on the definition of the kilogram. The main purpose of the proposed change is to find an independent definition. Another purpose is the possibility of linking the definition to an exact value (similar to the speed of light.)
The formal decision for the change was made during the 26th meeting (13–16 November 2018) of the General Conference on Weights and Measures (CGPM).
The motivation behind the change of the definition of the mole can, for example, be found in the resolutions of the 24th meeting (17–21 October 2011) of the General Conference on Weights and Measures (CGPM); however, the discussions and preparations started already much earlier.
On the possible future revision of the International System of Units, the SI
(…)
considering
(…)
that of the seven base units of the SI, only the kilogram is still defined in terms of a material artefact, namely, the international prototype of the kilogram (1st meeting of the CGPM, 1889, 3rd meeting of the CGPM, 1901), and that the definitions of the ampere, mole and candela depend on the kilogram,
(…)
that it is also possible to redefine the mole so that it is linked to an exact numerical value of the Avogadro constant $N_mathrm A$, and is thus no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of $h$, thereby emphasizing the distinction between amount of substance and mass,
(…)
$endgroup$
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
add a comment |
$begingroup$
You have already mentioned the last definition of the mole before the proposed change:
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.
(…)
According to this definition, the mole still depends on the definition of the kilogram. The main purpose of the proposed change is to find an independent definition. Another purpose is the possibility of linking the definition to an exact value (similar to the speed of light.)
The formal decision for the change was made during the 26th meeting (13–16 November 2018) of the General Conference on Weights and Measures (CGPM).
The motivation behind the change of the definition of the mole can, for example, be found in the resolutions of the 24th meeting (17–21 October 2011) of the General Conference on Weights and Measures (CGPM); however, the discussions and preparations started already much earlier.
On the possible future revision of the International System of Units, the SI
(…)
considering
(…)
that of the seven base units of the SI, only the kilogram is still defined in terms of a material artefact, namely, the international prototype of the kilogram (1st meeting of the CGPM, 1889, 3rd meeting of the CGPM, 1901), and that the definitions of the ampere, mole and candela depend on the kilogram,
(…)
that it is also possible to redefine the mole so that it is linked to an exact numerical value of the Avogadro constant $N_mathrm A$, and is thus no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of $h$, thereby emphasizing the distinction between amount of substance and mass,
(…)
$endgroup$
You have already mentioned the last definition of the mole before the proposed change:
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.
(…)
According to this definition, the mole still depends on the definition of the kilogram. The main purpose of the proposed change is to find an independent definition. Another purpose is the possibility of linking the definition to an exact value (similar to the speed of light.)
The formal decision for the change was made during the 26th meeting (13–16 November 2018) of the General Conference on Weights and Measures (CGPM).
The motivation behind the change of the definition of the mole can, for example, be found in the resolutions of the 24th meeting (17–21 October 2011) of the General Conference on Weights and Measures (CGPM); however, the discussions and preparations started already much earlier.
On the possible future revision of the International System of Units, the SI
(…)
considering
(…)
that of the seven base units of the SI, only the kilogram is still defined in terms of a material artefact, namely, the international prototype of the kilogram (1st meeting of the CGPM, 1889, 3rd meeting of the CGPM, 1901), and that the definitions of the ampere, mole and candela depend on the kilogram,
(…)
that it is also possible to redefine the mole so that it is linked to an exact numerical value of the Avogadro constant $N_mathrm A$, and is thus no longer dependent on the definition of the kilogram even when the kilogram is defined so that it is linked to an exact numerical value of $h$, thereby emphasizing the distinction between amount of substance and mass,
(…)
answered 1 hour ago
Loong♦Loong
33.4k883172
33.4k883172
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
add a comment |
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
$begingroup$
Thank you. So mainly to decouple its definition from the kilogram. I personally find this a simpler definition. I also have many other questions such as why it wasn't just defined as Avogadro's constant in the first place, but I think there are already questions about that here. Actually I don't even quite get why this was a motivating force behind the decision exactly, the separation of the kilogram to the mole, but I'm sure I'll find out with some more reading.
$endgroup$
– Zebrafish
3 mins ago
add a comment |
Zebrafish is a new contributor. Be nice, and check out our Code of Conduct.
Zebrafish is a new contributor. Be nice, and check out our Code of Conduct.
Zebrafish is a new contributor. Be nice, and check out our Code of Conduct.
Zebrafish is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Chemistry Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fchemistry.stackexchange.com%2fquestions%2f110189%2fwhy-has-the-mole-been-redefined-for-2019%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
1
$begingroup$
related chemistry.stackexchange.com/questions/60767/…
$endgroup$
– Mithoron
36 mins ago