# Tag Info

3

The term "normality" stems from the older German term for equivalent concentration (die Äquivalentkonzentration), namely die Normalität, which was coined by Karl Friedrich Mohr. According to German Wikipedia which also refers to Straube's Der historische Weg der Chemie [1, p. 220], Mohr introduced the concept of normal solution and normality (as it's known ...

2

One of my good acquaintances spent a considerable amount of time on continuum sources in atomic absorption spectrophotometry. It is very much possible, perhaps there is one commercial instrument as well by Jena (Germany). The source was a xenon arc lamp. In those cases, it is better to use a special monochromator, which is called an echelle monochromator. It ...

4

Absorption bands are very small: smaller than the band which a typical monochromator is capable of isolating. If a continuum light source was employed, the absorbed band would be much smaller than the band which would be isolated by the monochromator and which would be read by the detector. This implies a low SNR (signal-to-noise ratio), and a very poor ...

2

Model of a crystal and deriving the expected diffraction image In single-crystal X-ray crystallography, the diffraction image is due to scattering of electrons in a crystalline sample. A convenient way of describing the electron density is to first specify crystal symmetry and mean atomic positions (coordinates), and then to describe in more or less detail ...

0

Where concentration matters ( burette ) there is rinsing to achieve stable and constant concentration. Where amounts matters ( flask ) there is no rinsing to achieve stable and constant amount.

0

For gas chromatography, boiling point is one of the most important determinants of elution time. For thin-layer chromtagraphy, that isn't true. The comments from @Molx and @Buttonwood on this question expound on this point quite well. @Molx: Thymol has a lower boiling point (232 °C) than Carvacrol (237.7 °C, both from Wikipedia), I'd bet this is the ...

-1

If you were to calculate the concentration of acid from the titration, and you add distilled water to the erlenmeyer flask, then yes, you would affect the [H3O+(aq)] since increasing volume with same number of moles decreases the concentration of the solute (or analyte) and thus increases the pH of the solution (because pH is -log(hydronium conc.)), ...

0

This is calculated by equating the moles of the two solutions. You are using $0.6402g$ of sodium fumarate in $100mL$ of solution. $$\text{No. of moles} = \frac{Given \ weight}{Molecular \ weight} = \frac{0.6402}{160.04} = 0.0040\ \text{moles}$$ $$\text{The concentration of the solution can be found easily} = \frac{0.0040}{0.1} = 0.04 \text{M}$$ If you ...

0

Your method in using the equivalent concept is correct, but the miscorrect in your solution is in determining the n-factor. Refer to the above equations and the calculation N-factorPoutnik N-factor Is the change of atom oxidation state multiplied by the number of atoms changing this state. Because the iodine is just an intermediate product to be titrated ...

0

To find the molarity $c$, you need to know the amount $n$ required for a titration: $$c(\ce{Na2S2O3}) = \frac{n(\ce{Na2S2O3})}{V(\ce{Na2S2O3})}$$ Unknown amount $n(\ce{Na2S2O3})$ can be found from the second balanced reaction: $$\ce{I2 + 2 Na2S2O3 -> 2 NaI + Na2S4O6}$$ $$n(\ce{Na2S2O3}) = 2\cdot n(\ce{I2})$$ Finding $n(\ce{I2})$ is trivial if you ...

20

Yes, you can use a common stove to test for cations. But a stove is designed to minimize the risk of incomplete combustion (which could lead to production of carbon monoxide), hence its flame always appears as an intense blue flame. Such color contamination could be problematic when testing for cations. In contrast, the combustion (and the color of the flame)...

5

Flame emission (or better atomic emission) does not care whether your starting compound was ionic or not. Everything decomposes into flame either into atoms or very simple molecules. The blue color you see from the flame is also from very small molecules which exist in the flame. https://en.wikipedia.org/wiki/File:Spectrum_of_blue_flame.png Ordinary flame ...

3

When you ask how to remove borax, I assume it is Sodium tetraborate decahydrate (Wikipedia). Thus, I agree with @andselisk of using $\ce{Ba^2+}$ solution to precipitate it. Even though it is seemingly an excellent answer, the reference given and the text body are in German, and I didn't understand it much. :-) Thus, I want to give some clues to make it sense....

4

Lehrbuch der analytischen und präparativen anorganischen Chemie by Jander et al. [1] suggests to precipitate borate with $\ce{Ba^2+}$ in neutral solution beforehand as barium(II) thiocyanate is one of the few barium(II) salts actually soluble in water, or use an excess of $\ce{Fe^3+}$ to make sure all the interfering anions are precipitated. From [1, p. 358]...

1

As you have calculated, 500 ml of a 10 % HCl solution contain about 1.44 mol HCl. Thus the concentration is about 2.9 mol/l. Therefore, you cannot prepare this solution by diluting a solution with c = 0.5 mol/l HCl.

2

First of all, check the expiry date. In general HCl solutions are secondary standards. 1 N is just a approximation. You need to standardize it every time with a primary standard such as sodium carbonate. On the other hand, constant boiling HCl is indeed a primary standard. It is not very well known, perhaps because modern analytical chemists have become ...

5

This terminology is specific to EPA and it is not universal, because there are so many legal issues associated with any environmental analysis. They have to be extremely careful at each and every step (it may cost someone millions because of a wrong analytical result). Hence the reason for various "blanks." The language of those methods is official and the ...

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