13 votes

How to distinguish silver chloride, bromide and iodide?

Nilay Ghosh's method is excellent, but it does not work if the original deposit is a mixture of the three precipitates $\ce{AgCl, AgBr, AgI}$. In this case, it is first necessary to get rid of the ...
Maurice's user avatar
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11 votes
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How to distinguish silver chloride, bromide and iodide?

Aqueous ammonia should do the trick. Silver chloride is soluble in dilute ammonia solution. Silver bromide is sparingly soluble in dilute ammonia solution. Silver iodide is very slightly soluble in ...
Nilay Ghosh's user avatar
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8 votes
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Chemical Test for Hydrogen

There are metals that promote the catalytic oxidation of hydrogen in air, such as platinum and palladium. While these are fairly expensive in bulk, there are reasonably inexpensive sensors which use ...
DrMoishe Pippik's user avatar
8 votes
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False positive test for chloride ions during lab practical

I agree with Maurice's answer, here I add some details: Moisture in the air may stabilize nitric acid against decomposition, which would keep the fumes white or at least more white. Ammonia can ...
Oscar Lanzi's user avatar
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7 votes

Chemical Test for Hydrogen

I would be inclined to create two half-cells, the one a standard hydrogen electrode, and the other, the gas under test, connected with a narrow tube as recommended with the Standard Hydrogen Electrode ...
Stephen Elliott's user avatar
7 votes
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Why is there a yellow solution formed upon reaction of silicon tetrachloride with water?

The yellow color is indeed due to an impurity. According to Wikipedia: Silicon tetrachloride is prepared by the chlorination of various silicon compounds such as ferrosilicon, silicon carbide, or ...
Oscar Lanzi's user avatar
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7 votes

False positive test for chloride ions during lab practical

If your powder, mixed with "mildly" concentrated sulfuric acid, produces white fumes that react with ammonia, the white fumes may be $\ce{HCl}$ , $\ce{HBr}$, or $\ce{HNO3}$. But if it is $\...
Maurice's user avatar
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6 votes

What is the role of a monochromator in atomic absorption spectrometer?

The answer by @bobthechemist is clear, concise and correct and I upvoted it. However, I think the first figure in bobthechemist’s answer does not fully convey the significant complexity of the ...
Ed V's user avatar
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6 votes
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Hydrogen sulfide in acetone?

The solubility of both ammonia and hydrogen sulfide in various polar solvents is reported by Short et al1. The table below, from this reference, gives values as volumes of gas per unit volume of ...
Oscar Lanzi's user avatar
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5 votes

Why are fluorine-19 NMR spectra less affected by paramagnetic centers than other common nuclei?

$\ce{^{19}F}$ has similar NMR properties to $\ce{^1H}$ except in particular for the much larger chemical shift tensor terms and resulting larger chemical shift anisotropy (CSA). As a result CSA ...
Buck Thorn's user avatar
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5 votes

Can glycerol slow down the kinetics of an inhibitor going to a binding pocket of a target enzyme?

I am wondering if the glycerol, ca. 8 percent from my protein stock may slow down the kinetics that determine the binding of the inhibitor to the protein? When you change the solvent, a lot of things ...
Karsten's user avatar
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4 votes
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pKa and pKb in solvents other than water

Bruckenstein and Kolthoff give some values in the abstract, which is available in the free preview. Notable among acids: perchloric acid, $pK_a=4.87$; hydrogen chloride, $pK_a=8.55$. Also given is an ...
Oscar Lanzi's user avatar
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4 votes

Chemical Test for Hydrogen

Small amounts of hydrogen can be tested by methods using electrochemistry, as illustrated in two answers above. Larger amounts, on the order of 50 - 100 mL, can be tested and identified by the unique ...
James Gaidis's user avatar
4 votes

Number of significant figures to use in reporting the concentration of the titrand in acid-base titration

You said that you have done seven titrations, i.e., you have the set of concentrations $\{c_1, c_2, \ldots, c_7\}$. I offer you the following standard statistical approach to inform your concentration ...
Metal Storm's user avatar
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4 votes
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How and when do redox indicators work?

It is fully analogical to pH indicators and acid-base titrations. The potential of the equivalence point should lay within the potential range of indicator transition. The optimal case is when the ...
Poutnik's user avatar
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4 votes
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Would ferrous ion give the flame test?

Zinc, cobalt and iron salts do not give a color to the flame, whatever the method used, and whatever the chosen salt. Try to do it yourself ! It is easy. Anybody can do it. You may see a yellow color ...
Maurice's user avatar
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3 votes

How to effectively replace DMSO with LC–MS-compatible solvent for the samples from a well plate?

The standard way to remove water and replace with volatile solvents for microscopy is with a dehydration series, e.g., replacing water with ethanol, and then ethanol with acetone. To more thoroughly ...
DrMoishe Pippik's user avatar
3 votes
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What is alkalimetry?

IUPAC's current terminology for the kinds of titrations is based on the following classification [1, p. 580]: nature of end-point detection (coulometric, potentiometric, amperometric, conductometric, ...
andselisk's user avatar
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3 votes

Rhodizonic Acid and Silver Citrate?

I investigated silver rhodizonate, among other ions, in my master's thesis. Being a high symmetry oxocarbon $(D_\mathrm{6h}),$ it exhibits many interesting spectroscopic properties. The results are ...
Norberto Gonçalves's user avatar
3 votes

How to divide the peaks of two anion ions using ion chromatography?

A mixture of roughly-symmetric peaks can be achieved by a sum of exponential functions. $$f(x; \vec a, \vec m, \vec s) \triangleq a_{1}\exp\left(-\frac{1}{2}\left(\frac{x-m_{1}}{s_{1}}\right)^{2}\...
Galen's user avatar
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3 votes
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What is the equivalence point in the context of a redox titration?

As the ongoing reaction is $$\ce{5 Fe^2+(aq) + MnO4-(aq) + 8 H+(aq) -> 5 Fe^3+(aq) + Mn^2+(aq) + 4 H2O(l)}$$ the point of equivalence is when the initial molar amount of $\ce{MnO4-(aq)}$ is equal ...
Poutnik's user avatar
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3 votes

Role of MnSO4 in permanganometric titration

Both the oxidating ion $\ce{MnO4-}$ and reducing ion $\ce{C2O4^2-}$ are anions and therefore electrostatically repulsing each other, what makes their reaction slow. $\ce{Mn^2+}$ ions serve as catalyst,...
Poutnik's user avatar
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3 votes
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Does reduction occur well above the reduction potential?

You're right, the textbook statement is not entirely accurate. While applying a potential of +0.530 V, significantly higher than the standard reduction potential (+0.356 V), would thermodynamically ...
Saurabh Anand's user avatar
3 votes
Accepted

What can I do if a peptide won't go in solution in a biological assay?

So, it is a very unpolar peptide, and it did not go into the buffer solution, neither vortexing, ultrasonic treatment or gentle heating worked. The 3 mg of peptide was attempted to be solved with 10 ...
raptorlane's user avatar
3 votes

How can the double-layer capacitance be constant in the Helmholtz model?

To start forget for a second about double layer models and particularly details of the electrolyte or other medium adjacent the electrode. Assume you have a perfect conductor which you hooked up to a ...
Buck Thorn's user avatar
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2 votes
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What is a good strategy for fully quantitative X-Ray Diffraction on coal fly ashes?

I am the author of that paper. Reach out on linked in if you would like to discuss in detail. The bot deleted my previous message when I sent my linked in address. You can also get more information my ...
Ross Williams's user avatar
2 votes

How to interpret gas chromatography results?

The problem has nothing to do with gas chromatography. It has to do with the kinetics of a chemical reaction. Whatever the method used to get the concentrations, when you get the concentrations of the ...
Maurice's user avatar
  • 28.1k
2 votes

How to proceed with iodometric titration to determine caffeine concentration in liquid coffee?

Classical volumetric titrations are not selective. This means if there are multiple components in the mixture, they will react with the reagents used in the titration. Since coffee and tea are real-...
AChem's user avatar
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2 votes

What is alkalimetry?

Practically, the right meaning is the meaning used and/or assumed in given context, circumstances, community. Use, what is more usual in your region, or perhaps better, replace it by more universal ...
Poutnik's user avatar
  • 40.9k
2 votes

Methanol Ethanol butanol mixture assay via spectrophotometer

They have Significant differences in the C-H and C-O stretch areas that should resolve nicely at 2 or 1cm-1 resolution in a good FTIR. A multivariant analysis is necessary. I recommend a 3-bounce ...
jimchmst's user avatar
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