Questions tagged [experimental-chemistry]
This tag should be applied to questions relating to the theory, design, techniques or performance of chemical experiments. This includes but is not limited to theoretical structures, expected products, thermal calculations, and empirical analysis. Additional tags should be applied to narrow down the field of research.
1,548
questions
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10 views
How to prepare 0.25M citric acid solution using citric acid monohydrate powder? [closed]
How to calculate the quantity of solute (citric acid monohydrate) required for preparing 0.25M citric acid solution?
3
votes
1answer
77 views
How should you report measurements and uncertainty for a measuring cylinder with 0.5 mL graduations?
I understand that a common convention is to report the uncertainty of an analogue instrument as plus or minus half of the smallest scale division.
By this logic, a measuring cylinder with $\pu{0.5 mL}$...
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0answers
16 views
Regarding Baratchotoxin Stability period [closed]
How long the Baratchotoxin tipped darts be stable, like will it have the same toxicity even after 15 years with out being used
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1answer
50 views
Can anyone identify this instrument part and what instrument it comes from?
Can anyone identify this instrument part and what instrument it comes from?
0
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0answers
36 views
How did we find relative atomic masses in 18th century or early 19th century? [duplicate]
The atomic masses of atoms or relative atomic masses were known in the 19th century.
But how did they actually calculate that relative atomic mass?
What I think is that if we have a sample of an ...
-2
votes
0answers
35 views
Creatine Powder Purity Test
Main goal is to find out if a creatine powder is 100 percent ( or at least above 95) pure or not. ( There is a concern the supplements my students are using may have been made from low quality ...
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0answers
32 views
Does heat really necessary to mix substance?
For example when need to perform acid esterification (alcohol & acid), or alkaline transesterification.
In paper it's normally practiced to pre-heated the mix in the range 50-60 C before stirring
...
2
votes
1answer
69 views
What are the hydrodynamics behind a Soxhlet extractor?
So I'm trying to wrap my head around the physics of how a Soxhlet extractor works, not the chemical, solvent and chemical components part, but rather the physical, hydrodynamic, siphoning part : why ...
5
votes
1answer
115 views
Can I use the Winkler method as a way to measure the rate of photosynthesis?
I want to make an investigation where I measure how the color of light affects the rate of photosynthesis.
The idea is to put an Elodea plant in a test tube and shine with different color of light ...
0
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0answers
19 views
Values of Hammett Acidity function for differing concentrations of H2SO4?
I am styling the effect of the concentration of different catalysts on the hydrolysis of sucrose to study it's reaction mechanism. I will be using the Hammett-Zucker hypothesis to find the ...
0
votes
0answers
37 views
Glass fritted filter
Today I soaked my glass fritted filter with sulfuric acid 95% diluted 3 times. After many hours I wanted to check it but I found that the glass layer turned to grey or light blue color! I want to know ...
4
votes
0answers
48 views
Briggs-Rauscher reaction doesn't oscillate and turns blue with Vitamin C
I tried to recreate the Briggs-Rauscher reaction by using a solution of $\ce{H2O2}$, $\ce{KIO3}$, $\ce{H2SO4}$, $\ce{CH2(COOH)2}$, $\ce{MnSO4}$ and a soluble starch. I used this recipe.
In container ...
0
votes
1answer
60 views
Why are the relative masses of isotopes not close to whole numbers?
Understandably, the relative atomic masses of isotopes are often not close to whole numbers as they're adjusted for isotope abudandancy eg. $A_r(Cl)\approx35.45$. However, wouldn't one expect the ...
5
votes
0answers
42 views
How to experimentally determine the dissociation energy (electronegativity) between identical atoms?
I was reading on Wikipedia about how Pauling electronegativities are determined through
$$ \vert \chi_\ce{A} - \chi_\ce{B} \vert = \sqrt{E_\mathrm{d}(\ce{AB}) - \frac{E_\mathrm{d}(\ce{AA}) + E_\mathrm{...
1
vote
1answer
45 views
Continuous variable for graph of boiling point of different chain lengths
Looking at the boiling points of alkanes (for examples), many graphs plot boiling point against chain length :
However, there is an issue with the line of best fit- since chain length is a discrete ...
1
vote
1answer
40 views
Is it okay to use indicator as a powder instead as a solution in titration experiments?
My experiment involves titrating iodine solution against some sample solutions to find the amount of ascorbic acid in it. The indicator I'm using is 0.5% starch solution which will turn the solution ...
1
vote
0answers
49 views
Is there a way to calculate the rate constant of electrochemical cells?
I'm doing an experiment on temperature's influence on electrolysis of iron oxides and I need a way of measuring rate, preferably rate constant (k) or something similar. I've done some googling and ...
0
votes
0answers
13 views
What is the protocol for esterification reaction between nanocellulose and tartaric acid?
I am trying to prepare nanocellulose esters via esterification with Tartaric acid. I know that the traditional method employs a strong acid such as sulfuric acid. What would the process look like in ...
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votes
1answer
23 views
Will concentration of sodium hydroxide affect the result of chicken feather hydrolyzate if i don't standardized it?
The title of the paper:
Isolation and characterization of keratin from chicken feathers https://doi.org/10.1063/5.0002792
Here is the method:
Keratin was isolated by dissolving 5g of chicken feather ...
18
votes
2answers
2k views
Why is carbonic acid often ignored?
Water (distilled or not) picks up CO2 from the atmosphere, some of which dissolves to form carbonic acid (H2CO3), lowering the pH by a point or two.
From that it seems like carbonic acid would be the ...
1
vote
1answer
133 views
Can ferrous ions exist in an acidic solution?
Can Fe2+ ions exist in an acidic solution or will they always pick up available protons and become Fe3+? My hunch is they can't exist but I'm not really sure.
If the latter, does that mean that ...
5
votes
1answer
355 views
Fluorine detection in organic compounds
Many of you will know why I am asking this question. There is a lot of attention recently to the dangers of the so called Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS). In essence organic ...
-1
votes
1answer
30 views
Where does Aluminum Hydroxide come from in a reduction of a ketone by LAH? [closed]
The experiment was done in a Laboratory. A ketone was reduced with LAH in THF under reflux.
At the end of the reaction, the protocol stated to add water until there is no more H2 released. The H2 ...
0
votes
0answers
24 views
Representing units for concentration of a liquid (v/v)%
I'm doing an experiment which involves testing a particular solution in different concentrations. Since this is a liquid, the concentration should be represented in v/v % rather than w/v %. However, I'...
2
votes
1answer
237 views
What is the "frequency of occurrence" referring to in this paper?
In Zhou et al.(2018) 22. 10.1016/j.geoderma.2018.02.015, table 1 of the different microplastics refer to a "frequency of occurence".
Why does the % frequency of occurrence add up to >100%...
1
vote
1answer
85 views
What is the function of thin layer in thin layer chromatography?
I just learned about the thin layer chromatography, which I think is basically the same as the paper chromatography.
I am wondering what is the function of the thin layer? I mean, what's special about ...
0
votes
0answers
14 views
DI water vs. Tap water in ethanol-water and salt phase change reaction
We did a very simple lab like one you would do in highschool showing that you can seperate the phases of water and ethanol using salt. As simple as it sounds, we could not get it to work no matter ...
0
votes
2answers
65 views
What might cause overestimated measured pH value of sodium hydroxide solution pumped with carbon dioxide?
I tried an experiment at home where I had a $\ce{CO2}$ tank pumping $\ce{CO2}$ into a solution of $\pu{28 g}$ sodium hydroxide in $\pu{200 ml}$ water. The initial $\mathrm{pH}$ was $11.24.$
I expected ...
0
votes
1answer
33 views
How to apply a certain voltage vs SHE
For one of my projects, I must apply a voltage at the electrodes of -1V and +2V vs SHE. But my device potentiostat picks a voltages of 3V. How am i certain that it doesn't apply the voltage between -...
1
vote
0answers
26 views
How long do temporary dipoles last? [closed]
Theoretically, if you put 2 neutral atoms/compounds together in a controlled space with no external electrical fields, would a temporary dipole last forever, or would the jumping of electrons break ...
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votes
1answer
25 views
The meaning of USFDA (in cosmetics) [closed]
The full meaning of USFDA base on the definition of cosmetic meaning and production
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votes
1answer
70 views
Mixing hydrogen peroxide and sodium hydroxide doesn't lead to sodium peroxide anymore [closed]
I've been using same bottle of hydrogen peroxide and same bottle of 50 % of sodium hydroxide to make sodium peroxide for a month now. You could see the presence of sodium peroxide in the solution ...
2
votes
0answers
27 views
Solvent choice in imine formation from quercetin and poly(allylamine)
I am trying to react quercetin and poly(allylamine) to form imine on the repeating units. Poly(allylamine) is dissolved in water. The problem is the choice of solvent. Poly(allylamine) is soluble in ...
1
vote
0answers
38 views
Why is my Briggs-Rauscher reaction oscillating but failing to turn blue?
As the title says, I've constructed a Briggs-Rauscher reaction according to the ever-popular "Chemical Demonstration: A Handbook for Teachers of Chemistry" by B.Z. Shakhashiri (the same ...
0
votes
1answer
48 views
How is nitrogen gas passing through condensed water in the U-Tube while reducing metal oxides with ammonia gas?
In my school chemistry book, the experiment about the reduction of metal oxides with ammonia has a diagram of the set up as follows:
$$\ce{NH₃ + CuO → 3Cu + 3H₂O + N₂}$$
The tube entering the U-tube ...
1
vote
2answers
66 views
Just looking for some help with finding relative ratios of components in a mixture using proton NMR
G'day,
I am used to identifying molecular structure in isolation using proton and carbon NMR, but have never worked with a mixture before. The mixture relates to the following spectrum:
The spectra ...
0
votes
1answer
28 views
What would happen if I increase the pressure and temperature of a gas present in a container
Assume the gas to be a real gas and the container to be made of diamond or anything stronger than that. Take the amount of gas to be 2mL and the pressure is increased with the help of strongest ...
1
vote
1answer
132 views
Method to remove impurities from acetaminophen synthesis experiment
I'd like to know about impurities from acetaminophen synthesis experiment. Are there any impurities produced by oxidation of p-aminophenol? If there is any impurity produced by oxidation of p-...
0
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0answers
48 views
Best practices to obtain small quantity of sealed solution without oxidising entire solution?
I'm ordering liquid based chemicals which only come in large bulk quantities. These solutions have a shelf life of approximately 2 years unopened, but 2 - 3 weeks once opened and oxidation kicks in. ...
1
vote
0answers
36 views
How to prepare an emulsion (compounds in wt%)
I am trying to replicate an experiment to generate microparticles but I found myself confused about how to prepare the ingredients as some need to be weighed and dissolved before and I think the ...
1
vote
0answers
40 views
Differences in activated manganese dioxide synthesis
I've looked into preparations of activated manganese dioxide for some time now, and what confused me is the contrast between the original Attenborough method and some of the alternatives.
A solution ...
1
vote
1answer
63 views
NaOH + atmospheric CO2: Unexpected results troubleshooting
I've conducted an experiment where a solution of $\pu{4.2 M}$ $\ce{NaOH}$ was left exposed to atmospheric $\ce{CO2}$ for a period of time and titrated using potentiometric titration and potassium ...
2
votes
0answers
60 views
Analysis of reaction mixture by TLC and finding column chromatography condition
I am conducting an organic synthesis. Below is the TLC image.
I used dichloromethane:methanol:triethylamine=10:1:0.15 as eluent, but I stored it during 3 days, so it may be a little bit concentrated.
...
5
votes
2answers
111 views
Why do alkenes (olefins) burn hotter than alkanes (paraffins), even though alkanes are denser and more hydrogen-rich?
Burning hydrogen releases more total energy than combusting carbon, and all alkanes are denser as well, so why are flame temperatures for alkene molecules higher than their equivalent alkanes?
P.S.: ...
3
votes
1answer
82 views
Friedel–Crafts acylation of substituted anisole
I am attempting to form a synthetic route to a tetrasubstituted benzene compound. In the scheme, there is a step that requires the formation of a carbon–carbon bond in the C-6 position of a methoxy ...
6
votes
2answers
2k views
Which is a more accurate scale for a chemistry high school lab - a triple beam balance or a digital balance and why?
I would like to ask the experts of this chemistry community their opinions on which balance is more accurate and effective to use in a high school chemistry lab- a triple beam balance or a digital ...
7
votes
3answers
440 views
Choosing reaction stoichiometry in organic synthesis
Reading papers about organic synthesis, I see many cases like setting one material as 1.2 eq. I presume that reagents used more than 1 equiv are relatively inexpensive or less reactive than other ...
3
votes
0answers
148 views
How can I store reagent under inert gas?
I need to store some aliquots of 2,3,5-tribromothiophene. I searched for how to store reagent under inert gas, And I found this : https://avantilipids.com/tech-support/faqs/protect-from-oxidation
In ...
1
vote
0answers
35 views
Problem about TLC solvent and staining
I am conducting an organic synthesis involving 1-aza-18-crown-6-ether. I tried TLC, but they didn't work well. I have tried: (1) hexane+ethyl acetate in various ratio, (2) dichloromethane:methanol=3:1,...
0
votes
0answers
26 views
Why does pure alpha glucose powder clump when attempting to dissolve in water and become very hard?
I noticed that when I attempted to dissolve some pure alpha glucose powder in water, it would become hard and clump at the bottom of the beaker if I dumped it into the beaker all at once. It was ...
