Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange
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)...


7

The use of $\ce{NaI}$ in $\ce{MeCN}$ (a solvent in which $\ce{NaI}$ is quite soluble) is forming $\ce{Me3SiI}$ from the $\ce{Me3SiCl}$. The reason for doing this is $\ce{Me3SiI}$ is significantly more reactive with the triethylammonium enolate and will increase the yield of the TMS-enolate. You are correct in thinking that the white fume you see when adding ...


7

If your reaction has worked and you get the expected product, you should see following NMR data as the sought literature reported: $\mathrm{^{1}H}$-NMR: $\delta$ 3.44 (s, $\ce{6H}$), 4.85 (s, $\ce{1H}$), and 10.32 (broad s, $\ce{1H}$). $\mathrm{^{13}C}$-NMR: $\delta$ 54.1 ($\ce{2CH3}$), 98.6 ($\ce{CH}$), and 170.7 ($\ce{C_q}$). Instead, you got two ...


5

Sodium is a difficult ion to estimate at home. Since most sodium salts are water-soluble, colorimetric or spectroscopic methods are often employed, both of which I assume are not within arms' reach. Some alternatives: Speaking of sodium estimation in foodstuff, it is usually determined by Mohr's method which involves the precipitation titration of $\ce{...


4

The dilithium dimer exists- but it isn’t particularly common, and we usually only see it in the gas phase. Essentially, the 2s electrons interact and form a bonding orbital. (s-p mixing is particularly pronounced here, but I presume you don’t know MO Theory.) Due to the diffuse nature of lithium’s atomic orbitals, the bonding is pretty weak (Wikipedia ...


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]...


4

The answer from @Mathew Mahindaratne in my opinion correctly identifies what the OP has isolated. It remains to suggest how to get the required product. It may be a matter of salting out the aq phase, but there are other possibilities. Some observers may feel that given a literature prep from a respected group there is no need to alter it, however the OP has ...


3

The brown ring nitrate test is based on forming ferrous nitrosyl cation, with nitrous oxide formed from nitrates by iron oxidation in acidic solution: $$\begin{align} \ce{3 [Fe(H2O)6]^2+ + NO3- + 4 H+ &->3 [Fe(H2O)6]^3+ + NO + 2 H2O} \\ \ce{[Fe(H2O)6]^2+ + NO &->3 [Fe(H2O)(NO)]^2+} + H2O\\ \end{align}$$ Positive results are given also by ...


3

There is an image of a table provided by Chu and Thompson [1] listing isopropanol water solution densities: The essential data part is (weight % vs density): 77.87 0.8361 89.84 0.8069 99.91 0.7808 There is density gradient -0.0026 / 1 w%, resp. -0.00052 / 0.2 w%, determining purity by density via hydrometers is rather illusory. Some success ...


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....


3

If we have 2 variables with absolute uncertainties(+) $A \pm \sigma_A$ and $B \pm \sigma_B$ (+) expressed as standard deviations, but applicable to confidence intervals as well. Then $C = A \pm B$ has uncertainty $$\sigma_C = \sqrt{{\sigma_A}^2 + {\sigma_B}^2}$$ For $C=A/B$ or $C=A\cdot B$, $$\sigma_C = C \cdot \sqrt{\left(\frac {\sigma_A}{A}\right)^...


3

You could theoretically boil at the higher temperature but why would that be a requirement? Why would you require reflux specifically if you can actually heat the formic acid to higher temperatures under pressure? Heating should work on its own and degassing to drive the equilibrium should work with a back pressure regulator. However, most lab glassware ...


3

Ammonium nitrate is very soluble in water, so watering the soil will remove it, though, depending on the amount and dilution, it could then pollute streams, lakes and other bodies of water, possibly causing an algae bloom. Your best choice might be to experiment with nitrate-tolerant plants, such as lettuce, ornamental cabbage and rhubarb, or perhaps bell ...


3

Re-quoted misinformation leads to incorrect speculation. Here's what I've learned through practical experience over the years. Not recommending it but if need be, Dimroth's & Allihn condensers (as well as other types) can also be stacked. To reduce flooding, use larger joint sizes. I assure you: a 45/50, 150 cm, heavy walled Allihn works fabulously ...


3

The following is the comparison list from the top of my head: Oil for the oil bath is often available commercially, every batch has the same properties and is arguably easier to store and transport; sand bath requires sifted and refined sand (quartz sand, ideally). It all depends on what's easier to find a good supplier and storage for. Oil bath heats up ...


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 ...


1

If you look at the overall reaction, there is actually no gas produced, but there is a consumption of gas: $\ce{CH3(CH2)_n-OH + \frac{3}{2} (n + 1)O2 -> (n + 1)CO2 +(n + 2)H2O}$ So 1.5 mol of oxygen are consumed, while only 1 mol of carbon dioxide is formed, so the volume will be less if the temperature is maintained. To perform this experiment, you ...


1

The number of moles of solute does not decrease on dilution. For example suppose you add 2 moles of NaOH to 100cm3. Now if you dilute this solution to 1000cm3 you are still going to have 2 moles of NaOH. But now the total volume has changed ,hence the concentration also changes.


1

The keyword you should search is iodometric titration. Triiodide solutions are dark brown, just like the tincture of iodine. If you were to add thiosulfate ion (say from a buret) to the triiodide solution would become colorless. The change is not that sharp. Therefore this is not the way end point is detected. A small drop of starch is added. Starch makes a ...


Only top voted, non community-wiki answers of a minimum length are eligible