All Questions
15
questions
-1
votes
1
answer
182
views
Convention for writing concentration units
1st part of my question:
Q) The concentration of an NaCl solution is 1M. Express this in percent wt. by vol. unit.
Ans:
$$\text{In %(w/v) unit}=\frac{58.5\pu g}{1000\pu{mL}}\times \frac{100}{100}=5.85\...
- 201
-4
votes
1
answer
129
views
Is Avogadro's constant equal to 1? [closed]
The mole is defined to be exactly $\mathrm{mol}=6.02214076\cdot 10^{23}$ entities. Avogadro's constant is defined as $N_A=6.02214076\cdot 10^{23}\mathrm{mol}^{-1}$.
Then why is it not usual to write
$$...
- 109
23
votes
1
answer
6k
views
How much is 1 mμg?
So I stumbled on a research paper by Okuda and Takedatsu [1] that uses mμg as a symbol for the mass unit.
I couldn't find anything about this measure unit anywhere except a recommendation not to use ...
- 349
1
vote
1
answer
57
views
Question on notation
Here, when they write $v/(\mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-1}})$ is $0.30$ for the first row first column, do they mean that the value is $0.30\ \mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-...
- 197
0
votes
1
answer
5k
views
Meaning of mass concentration "units" % m/v [closed]
In a saline solution that is 5.750% (m/v) potassium iodide $(\ce{KI}),$ there are:
a) 5.750 mL $\ce{KI}$ per 100.0 mL $\ce{H2O}$
b) 575.0 mg $\ce{KI}$ per 10.00 mL of $\ce{KI}$ solution
c) 5.750 g $\...
- 11
0
votes
2
answers
4k
views
How are lowercase k and uppercase K used in general chemistry courses? [closed]
Where do lowercase k and uppercase K make appearances in general chemistry, and what do they signify?
- 41.2k
0
votes
2
answers
22k
views
How are lowercase m and uppercase M used in general chemistry courses? [closed]
Where do lowercase m and uppercase M make appearances in general chemistry, and what do they signify?
- 41.2k
17
votes
1
answer
8k
views
How to interpret parts-per notations? Is 1 ppb equal to 1 μg/kg?
In an article I recently submitted, a reviewer asked that I provide a concentration in μg/kg instead of ppb (parts per billion), and mentions that the later is not correct. I am not a chemist, and I ...
- 281
0
votes
3
answers
4k
views
Conversion from a PPB value to µg/m3 of Isobutylene
I have a quite simple problem, found a lot of information about it, but I am not sure anymore if I do my calculations right.
I own a sensor, which reports measurements in isobutylene units as PPB. So ...
- 111
0
votes
1
answer
56
views
Combination of several unit symbols when finding new pressure from ideal gas law
As a car is driven, the tires heat up and the volume and the pressure change. Calculate the new pressure of a 35.0 L tire initially at 235 kPa that expands to 36.5 L when it heats up from 15.0 °C to ...
user73841
6
votes
1
answer
725
views
Does adding prefixes to SI units make them no longer SI units?
Our chemistry professor said that "mg for mass, g/m3 for density, ms for time are all SI units".
I want to make sure now, even if we added a prefix to the unit, will it still be an SI unit?
4
votes
1
answer
3k
views
What does 10 Vols mean?
I am currently working on a project and the protocol says the following, "Wash resin 3 times 10 vols of the extract buffer." This is very confusing to me and I am not exactly sure what the 10 vols ...
- 141
-2
votes
1
answer
24k
views
What does the unit M stand for? [closed]
What does $\mathrm{M}$ signify in this pH calculation? To me, it just seems to be a random variable.
For example: $\ce{[H+]} = 1.0\times10^{-7}~\mathrm{M}$
I am not sure what the $\mathrm{M}$ is ...
- 435
37
votes
6
answers
6k
views
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 ...
- 2,335
6
votes
4
answers
80k
views
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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