# Tag Info

Accepted

### How to interpret parts-per notations? Is 1 ppb equal to 1 μg/kg?

You are correct suggesting that 1 μg/kg implies 1 ppb, however the reverse is not true. For instance, 1 ppb can also be 1 nmol/mol, and the reader will never have a chance to deduce which one is it ...
• 38.4k
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### How much is 1 mμg?

Looks like in 1966 there were still residues of double prefix notation in use. Here's an entry from Russ Rowlett's compilation of units on ibiblio.org (Rowlett): millimicro- (mμ-) an obsolete metric ...
• 1,379

### Why do we still need to know about the Rankine temperature scale?

Rankine is commonly used in the aerospace industry in the United States. Rankine is to Fahrenheit what Kelvin is for Celsius. So when people in the United States were creating programs and using ...
• 491
Accepted

### What is a Herzberg?

Herzberg filtration speed: The time taken to filter $\pu{100 mL}$ water at $\pu{20 ^\circ C}$ through a filter area of $\pu{10 cm2}$ at a constant pressure of $\pu{5 cm}$ water column (Thomas ...
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• 44.3k
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### Where does the label ‘Dq’ to denote the field split in coordination compounds come from?

I currently happen to have the book by Figgis that Max mentioned. Chapter 2 is devoted to a mathematical formulation of crystal field theory, which I did not bother reading in detail because I do not ...
• 71.7k
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• 1,058

### Why do we still need to know about the Rankine temperature scale?

I am currently studying mechanical engineering in the US, and I have used Rankine. It is used similarly to Kelvin. For example, in my thermodynamics class we used it to analyze various heat engines. ...
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### Is zero-point vibrational energy an intensive or extensive property?

Mathematically, an extensive property $f$ is one for which $f(\lambda x,\lambda y,z) = \lambda f(x,y,z)$ for extensive variables $x$, $y$, and intensive variable $z$. For example, the Helmholtz free ...

### Which unit should I use for m/z?

TL;DR: According to current IUPAC recommendations, $m/z$ is an abbreviation for a dimensionless quantity. Use of thompson unit is indeed currently discouraged. There is an overview provided in ...
• 38.4k
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### Can someone intuitively explain the reason for the units of entropy (J/K )?

The units of of energy over temperature (e.g. J/K) used for entropy in the thermodynamic definition follow from a historical association with heat transfer under temperature gradients, in other words, ...
• 22.7k

### What is the dimension of molar mass?

According to ISO ISO/IEC 80000 Quantities and units, BIPM The International System of Units (SI), IUPAC Quantities, Units and Symbols in Physical Chemistry (Green Book), NIST Guide for the Use of the ...
• 4,824

### Can Rydberg constant be in joules?

Rydberg constant $R_∞$ is usually given in reciprocal length units historically and because it's determined from hydrogen and deuterium transition frequencies [1]. Current value (in $\pu{m-1}$) is ...
• 38.4k

### How to correctly write "7 apples" according to the international system of units (SI)

Mole is just a scale factor I find this description very intuitive: A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly 12 grams of ...
• 91
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### Is it possible for me to derive Avogadro's number?

To determine Avogadro's number you have to measure the same unit at the atomic and macroscopic scales. This was first achieved by Millikan who measured the charge of an electron. The charge of one ...
• 4,392
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### How to determine omitted units in a publication

These are degrees Celsius. To prove that, you could search JACS for the publications of the same year/issue for the temperature-related physical constants such as melting point: Douglas et al. [1] ...
• 38.4k
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### Uncertainty when beaker goes by 50s

A real beaker says "approximate volume". So the volume is approximately between 100 mL and 150 mL. So maybe 125 mL with an uncertainty of 25 mL. Your daughter would know best because she ...
• 41.3k

### What term should I use when I am quantifying the amount of matter, mass or weight?

Because of the reasoning provided by you, i.e. mass is universal, and weight is the product of mass and magnitude of the local gravitational acceleration, I suggest to stay at mass. (A purist's view, ...
• 30.5k

### What is the correct unit for the equilibrium constant?

By definition, the equilibrium constant has no units, as we're supposed to be using active masses instead of the molarity/ concentrations of the respective substances. Active mass is a unit-less ...
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$K$ should be a unitless value. Otherwise, you'd get a nonsensical unit when you try to take the log of the unit. Each component of the product $K$ is usually an activity, which is frequently similar ...