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0

From Wikipedia, https://en.wikipedia.org/wiki/Thermodynamic_activity: When a 0.1 M hydrochloric acid solution containing methyl green indicator is added to a 5 M solution of magnesium chloride, the color of the indicator changes from green to yellow—indicating increasing acidity—when in fact the acid has been diluted. Although at low ionic strength (< ...


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 ...


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.


-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.)), ...


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{...


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)^...


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)...


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

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 ...


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 ...


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 ...


0

First of all I would consider the necessity, price and complexity of the pressure and try to carry out the reaction in standard laboratory glassware for longer time (checking the content of the desired product every duration period pointed in your instruction, e.g. 3 hours, 6 hours, etc.). If you get a good yield at ambient pressure this may save your ...


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....


0

The ammonium nitrate dissociate in water: $$\ce{NH4NO3 -> NH4+ + NO3-}$$ The $\ce{NH4+}$ and $\ce{NH3}$ form together the ammonia $\mathrm{pH}$ buffer with $\ce{NH4+}$ acidity constant $\mathrm{p}K_\mathrm{a}=9.25$: $$\mathrm{pH}=\mathrm{p}K_\mathrm{a}+ \log { \frac {c_{\ce{NH3}}}{c_{\ce{NH4+}}}}$$ The titration curve as $\mathrm{pH}=f(V)$ is the most ...


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]...


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 ...


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.


0

When HCl reacts with zinc or any other active metal such as aluminium, hydrogen is produced. This is what your textbook tells you. Whats is perplexing is the appearance of "fog" in the Erlenmeyer. In the beginning there is air above the liquid. When hydrogen evolution starts, the flask begins to fill with $\ce{H2}$ gas and creates enough pressure to displace ...


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

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 ...


0

I genuinely don't think citric acid would do that for large amount of soil. Yet, there are some microbial processes to remove nitrates from soil though (Ref.1): Abstract: The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the ...


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 ...


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 ...


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 ...


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 ...


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 ...


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