Questions tagged [notation]

A system of written symbols used to represent qualities or quantities, elements or molecules, or formulas in general. Usually a notation follows a convention or a guideline, often published by IUPAC-IUPAP. This tag should be used for questions regarding the proper use of a notation or misleading or uncommon notation in the scientific literature. Do not confuse this tag with the [nomenclature] or [terminology] tags.

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3
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1answer
3k views

What is the meaning of the “colon” notation in chemical formulas?

For example PEDOT:PSS and P3HT:PCBM.
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6answers
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May I treat units (e.g. joules, grams, etc.) in equations as variables?

Suppose I have two units, Tonks, $T$, and Borks, $B$, as well as the equation $\frac{50T}{20B}=x$. May I manipulate the equation as though $T$ and $B$ were the kinds of symbols that we learned to ...
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2answers
519 views

Proper dash to use for negative charge

What type of dash does one use when indicating something like F$^{-}$? I assumed it was a minus, since you indicate positive charge with a +, but there is one professor I know who insists that it ...
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0answers
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Raoult's law: is the molar fraction the molar fraction in the entire system?

I have two physical chemistry textbooks, one by Atkins and one by Levine, which seem to differ in their notation used when describing Raoult's law. Atkins talks about the molar fraction term in ...
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1answer
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Why do we sometimes write reactants above the reaction arrow?

We write: \[\ce{Alcohol ->[\ce{KMnO4}] Acid}\] The alcohol forms a carboxylic acid, i.e. gains an $\ce{O}$ from $\ce{KMnO4}$. This means $\ce{KMnO4}$ is a reactant! Then why is it written above the ...
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3answers
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What is the meaning of the “dot” notation in chemical formulas?

For example for 4 given elements A,B,C,D, what's the meaning of $\text{AB} \cdot x \text{CD}$?
3
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1answer
87 views

Is there any abbreviation for hydrates?

I'm getting tired of writing out the full formulas for hydrates, adding $\ce{.$x$\,H2O}$ to all formulas. I'm wondering if there's standard shorthand for these.
3
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1answer
108 views

Single line equilibria notation

I'm reading a paper with a reaction scheme where an enzyme binds loosely to inhibitor reversibly and then the Enzyme-Inhibitor complex undergoes another reversible conformational change to a tightly ...
3
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1answer
919 views

X[Y|Z] formulas

I often find formulas of minerals where some element symbols are grouped within square brackets and separated by a vertical bar. An example can be brochantite, whose formula I find expressed as $\ce{...
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1answer
695 views

What would be SMILES notation for a compound with delocalized bonding?

For example, the cyclopentadienyl rings in ferrocene $\ce{Fe(}\eta^5 \ce{-C5H5)2}$ are often drawn with delocalized electron circles in them instead of explicit pi bonds. The Wikipedia article for ...
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3answers
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Proper typography of “NOx”

I am a journal typesetter, and recently I came to a problem that I'm not sure I know to solve. The question is how to properly typeset the "NOx" abbreviation for nitrogen oxides. Which is ...
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1answer
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What is the correct chemical formula for monosodium glutamate?

Recently, I am interested with home materials and I discover that the chemical symbol for MSG or monosodium glutamate is $\ce{C5H8NO4Na}$. My problem is shouldn't it be $\ce{NaC5H8NO4}$ as we always ...
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What does the ‘−1’ superscript mean in units?

For example, the rate of a chemical reaction can be expressed in $\mathrm{mol}/\mathrm{L}^{-1}/\mathrm{sec}^{-1}$. Why is it ‘−1’ and not, say, ‘−2’? Does it change the meaning if the minus is removed ...
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1answer
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Empirical formula of Berthollides

Can the empirical formula be defined for berthollides? Is it equal to the molecular formula, or it can't be defined?
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1answer
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What do (R) and (Z) mean in chemical names?

So, I'm confused on the notation my professor uses in a certain question; could someone explain. He says: Draw the structure: (R)-(Z)-chloro-4,6,-dimethyl-3-octene I get everything after '(z)' I'...
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1answer
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What are t2g and eg in CFT?

In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts. The upper part with higher energy is the $\mathrm{e_g}$ and the lower part with lower ...
3
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1answer
751 views

Fractional Subscripts?

What is the physical meaning when we have an empirical formula with fractional subscripts such as $\ce{LiMn_{1-x}Fe_{x}PO4}$ $(0 \le x \le 1)$? This an example of the paper the notation above is ...
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1answer
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What is the correct net ionic equation for the neutralization of phosphoric acid? [duplicate]

What is the net ionic equation for the reaction between phosphoric acid and sodium hydroxide? I came up with \begin{align} \tag1 \ce{H+ + H2PO4- + OH- &-> PO4^3- + H2O},\\ \tag2 \ce{H+ + OH- &...
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1answer
2k views

Significant figures used to imply stated error?

The question reads, " express each of the following quantities using significant figures to imply the stated error". a)$2.3 \pm 0.001$ b)$1.989 \pm 0.0003$ I think the first one is 2.300 because ...
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1answer
142 views

About the way chemicals and molecules are represented

The standard way of representing molecules with letters like $\ce{C}$ for Carbon, $\ce{O}$ for Oxygen etc.; and a lot of lines and double lines like a graph from Graph theory where each letter is a '...
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1answer
615 views

Structure that breaks InChI

I am currently testing a piece of software that generates the InChI for a given structure. I also want to test error situations as end users will also deliver the mol files that will be used as input ...
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1answer
140 views

Empirical and Molecular Formulae

I'm not a chemist, and nor do I study chemistry so please try to be gentle. Glucose has the molecular formula $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$ and the empirical formula $\mathrm{C}\mathrm{H}...
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1answer
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Which ions are accounted for in total and net ionic equations?

There are a number of things I don't understand about ionic equations. First off, when you do net ionic equations, is it correct that you're only focusing on precipitates? The way I understood it, ...
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2answers
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Should the 'a' in the acid dissociation constant (Ka or pKa) be capitalised?

In science, the negative logarithm of the acid dissociation constant is denoted $\mathrm{p}K_\mathrm{a}$ or $\mathrm{p}K_\mathrm{A}$ depending on the source (lowercase "a" or uppercase "A"). Since it ...
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1answer
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What does “Anal. Calcd.” stand for written out?

I'm wondering what the abbreviation "Anal. Calcd. stands for exactly. It is put in front of calculated (expected) values for elemental analyses. "Analytically calculated" makes no sense for me, but ...
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1answer
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What's the convention for the symbols of enthalpies of formation, reaction, etc.?

I frequently encounter two ways of writing enthalpies of some process, e.g. for the enthalpy of formation: $\Delta_{r} G$ (or $\Delta_{R} G$) $\Delta G_{r}$ (or $\Delta G_{R}$) On the IUPAC Gold ...
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1answer
144 views

What does “/2” in the structure of calcium benzoate mean?

Please see the following figure. This is from the high school chemistry book of my son. He wants to know what does that /2 after $\ce{-COOCa}$ mean. The book is a non English one. And I have changed ...
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3answers
4k views

How do we represent a molecule in text form?

How do we represent a molecule in text form? A molecule, as a computer scientist I see it as a connected graph of atoms. A connected graph means that beginning at any atom, there is a path to any ...
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1answer
3k views

Notation “5% solution”

What does 5% aqueous solution of glucose mean? Note that it's just 5% and not 5%w/w. Do we assume it to be w/w? The question is If the osmotic pressure of 5% aqueous soultion of glucose is $\pi_1$ ...
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2answers
385 views

Significant Figures in almost-scientific notation

For a homework assignment on significant digits, I have to find the number of significant digits in the number $0.40 \times 10^3$. I know that in scientific notation, the number of significant digits ...
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2answers
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Why is ethanol written as C2H5OH not C2H6O?

This is balanced equation of fermentation of glucose: $$\ce{C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)}$$ I know that the result of glucose fermentation is ethanol ($\ce{C2H6O}$). What represented in ...
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1answer
51 views

What does $\mathrm{A}_r(\mathrm{H})$ represent when calculating the average natural weight of an elemental atom?

I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to: Calculate the atomic mass of hydrogen $\mathrm{A}_r(\mathrm{H})$ (...
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1answer
222 views

Surface Functional Groups/Notation

I'm reasonably unfamiliar with chemical notation, and recently I've come across something I'm not sure how to interpret. In this article, the authors refer to the "surface groups" denoted by $\ce{#Ti-...
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2answers
3k views

Chemical formula of ethanol and other carbon compounds

Should chemical formula of ethanol be written as $\ce{CH3CH2OH}$ or $\ce{C2H5OH}$? And whats the logic behind it? I have seen the former being used more often, so why is ethane represented by $\ce{...
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4answers
233k views

How do I type a simple chemical equation in Microsoft Word?

How do I type a simple chemical equation in Microsoft Word? I can do subscripts, but long arrows are more difficult. I can't get them to align with the text. Also, I can't figure out how to put a ...
41
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1answer
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Why is methane's molecular formula conventionally “CH₄”, while water is “H₂O” (among others)?

While revisiting some of my old notes about the Miller-Urey experiment, I stumbled across the "equation"... Electricity + $\ce{CH4~/~ NH3~/~H2O~/~CO}$ = Amino Acids This got me thinking. ...
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2answers
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What does this lambda–sigma notation mean?

I am currently reading the CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data by John C. Tebby (CRC Press, 1991) and on several figures (ex. pages 9 to 14) there is a caption that reads ...

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