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.
1,292
questions
-1
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0answers
26 views
What is meant by position 5' or 3'
I'm a self-learner that likes to keep up with current research. However, I can't find what is meant by expressions such as 5' or 3' positions on chemical structures. But , in particular, what is meant ...
-2
votes
0answers
12 views
Determination of Phosphorous by Quimociac Reagent [closed]
Please I face very strange problem, that’s appearance of effervescence the Aliquote of digested sample after adding Quimociac reagent.
Please allow me to tell you further information :
1- my sample ...
0
votes
1answer
33 views
The rate of change in pH v.s Temperature
I have somewhat established that there is a linear relationship between change in pH of carbonic fizzy drinks over time. I also realise that the pH increases linearly faster for the same carbonated ...
-2
votes
0answers
17 views
How to explain the nature/properties of a chemical compound? [closed]
For example; "Explain the properties of ammonium, or carbon dioxide, or aluminum oxide." Is there any format or rules or specific equations to properly answer such questions?
-2
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0answers
23 views
Is there any numerical comparison between phosphodiester bond and hydrogen bond in dna? [closed]
I am looking for a good reference on the numerical comparison of the phosphodiester and hydrojen bonds in dna. I am a mathematician and I do not have to much background in the chemistry and will be ...
1
vote
2answers
73 views
Why is absorbance in UV-VIS spectrometer negative even after calibration?
I was collecting data to plot a calibration curve using pure beta-carotene sample. Prepared 5 different concentrations of beta-carotene dissolved in methanol. Pure methanol was used as blank. However, ...
4
votes
2answers
382 views
How does pH of soda drink vary with time
Basically I have done an experiment where I measure the pH of my soda drink at a specific temperature over $\pu{45 min}$. At every temperature, the $\mathrm{pH}$ of my soda drink increases, but much ...
0
votes
0answers
24 views
Why does peak decoupling occur in H-NMR spectra?
For example, when we analyze the conversion of some chemical compound, certain characteristic areas tend to decrease (ok).
However, why can a peak (i.e., one peak) generate smaller peaks (i.e., more ...
0
votes
0answers
23 views
Vitamin C Titration Mechaism [closed]
Could someone, please explain the mechanism of how a vitamin C titration with potassium iodate, potassium iodide, hydrochloric acid, and a starch solution works? This is assigned for an individual lab ...
-2
votes
0answers
18 views
Reaction Rate Laws [closed]
I have a general question about reaction rate laws, its mostly theory. The question is about the Zero-, First-, and Second-Order reaction rates. I did a Crystal Violet, and $\ce{NaOH}$ reaction, and ...
1
vote
2answers
71 views
Reaction between copper (II)chloride and aluminium foil [closed]
When I reacted copper chloride and aluminum foil instead of getting the brown color I got green color. Can anyone share their procedure where the experiment actually succeeded?
1
vote
1answer
30 views
How to determine the pH of citrate buffer system
I used this table (http://microscopy.berkeley.edu/Resources/instruction/buffers.html) to make a citrate buffer system. The Pka value is 6.4, and I multiplied the solution by ten to make a larger batch....
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votes
0answers
22 views
Could I polymerize or cross-link agar biopolymer to increase molecular weight? [closed]
I have synthesised a biomaterial using 12 grams agar powder, 18 grams glycerol and 400ml water. I have tried different formulas mainly being reducing the amount of glycerol and water but the physical ...
-1
votes
1answer
35 views
How is silica gel made? [closed]
How is silica gel prepared from sand (after extracting it). How many ways can it be used? Is there a way to make it without an oven?
4
votes
1answer
67 views
Fractional index in a chemical formula of metal oxide
I have just read an article in which they used $\ce{WO3}$ and $\ce{WO_{2.9}}$ as precursors, whose objective was to form $\ce{WS2}$, in an atmosphere of argon by CVD. In one boat there is the powder ...
-1
votes
1answer
43 views
Sodium hydride 60% dispersion in mineral oil [closed]
I've got a bottle of sodium hydride 60% dispersion in mineral oil. It's not "in mineral oil" it's just powder with an oil coating. I'm using it in an inert reaction, is there a way to remove the oil?
3
votes
1answer
74 views
Is there a list of must-have columns for LC-MS/MS used in biochemistry/clinical lab setting?
Considering a wide variety of chromatographic columns used for (U)HPLC based on
phase type (normal or reverse);
column dimensions (geometry, length, inner diameter);
particle material $(\ce{SiO2},$ $\...
0
votes
1answer
35 views
Decomposition reaction of tin(II) nitrate [closed]
What are the products formed when $\ce{Sn(NO3)2}$ is subjected to high temperatures?
I searched over the internet but I didn't get any satisfactory answer.
-2
votes
0answers
25 views
What is the role of calcium hydroxide when mixed with agar? [duplicate]
From a Youtube video, the person adds a mixture of calcium hydroxide powder and water (to form a sort of paste) into a mixture of agar / water. I could not determine the exact ratio but it was ...
1
vote
0answers
28 views
To get clear plasma out of a minute particle (such as fibrin), is it necessary to vortex sample before centrifugation? [closed]
I'm going to analyse plasma samples that contain a lot of fibrin. It is necessary to centrifuge the samples to be able to pipette the plasma. After the samples are centrifuged I can't vortex them ...
0
votes
2answers
37 views
Reproducibility and Standard Deviation [closed]
Would a set of chemical data with a relative standard deviation of 0.6% or 20% be more reproducible?
My reasoning is that because it's easier to make mistakes and have a wide range of data, the 20% ...
-3
votes
1answer
31 views
why is water not compatible with lewis acids in a friedel-crafts alkylation [closed]
I know that it destroys the lewis acid character but that doesn't tell me anything.
1
vote
2answers
62 views
How are reaction enthalpy and entropy affected by temperature
The equation for Gibbs Free Energy demonstrates how the standard change in Gibbs Free Energy for a reaction is affected by temperature.
$$\Delta G^\circ = \Delta H^\circ - T\,\Delta S^\circ$$
...
1
vote
1answer
43 views
Fehling's solution turning yellow and then black?
While testing for formaldehyde (an aldehyde), I added Fehling's solution to the sample and let the test tube simmer in a water bath for some time. I returned ~15 minutes later to see a black/dark grey ...
1
vote
0answers
12 views
Ammonia Vapor Absorption Refrigerator
I am working on fabricating the icyball system. I am planning to charge it with the help of convex mirrors. Whether it is necessary to create a vaccum inside the refrigeration closed cylinders before ...
4
votes
0answers
36 views
membrane for a reverse osmosis desalination experiment
We are second year cram schoolers , we are currently working on a project tackling water desalination by reverse osmosis and are required to do an experience. During the process, we encountered some ...
1
vote
0answers
36 views
How to assign initial and final states of iodine transitions in its spectrum?
In an experiment, I gently heated iodine crystals to create vapors and then observed it absorption spectrum with a spectrometer. The temperatures throughout were moderate (maximum $40^\circ\text{C}$). ...
2
votes
0answers
44 views
Observing bands which I shouldn't be!
I performed the iodine spectrum experiment to observe vibronic transitions. I heated the iodine crystals to produce vapors (at a little above room temperature) and observed absorption spectrum with a ...
0
votes
1answer
30 views
Why does Calcium (specifically Calcium Carbonate) inhibit the Citrate buffer system?
Is it because citrate chelates calcium and then is unable to react with other chemicals being added? If so can someone explain this reaction to me, or if not provide what the reason is? If anyone has ...
-1
votes
2answers
96 views
Figure out how many deuterium atoms in a 3 microgram ice core sample
I'm in an introductory Chemistry class and ran into a Pearson problem, that no-one in our class including our professor has been able to truly figure out.
I know the solution is $4.69 \times 10^{13}$...
0
votes
0answers
29 views
How will the dielectric constant of water change when ethyl acetate is added?
How will the dielectric constant of water change when ethyl acetate is added?
The $\mathrm{p}K_a$ value of weak acids in aprotic solvents will be lower than in protic solvents because the dielectric ...
0
votes
1answer
31 views
Independant variable for Asprin pill titration with NaOH solution [closed]
I am assigned to do an independently designed chemistry experiment for school. I want to do titration of Aspirin pills with NaOH solution using Phenolphthalein as indicator. I am struggling to find ...
2
votes
2answers
53 views
Lab goggle recommendations?
I'm taking my first chemistry class with a laboratory component this quarter. My first laboratory session was earlier this evening (observing simple metathesis reactions). While I found the lab work ...
1
vote
1answer
88 views
Does Glycerol give silver mirror test with Tollen's Reagent?
I did an experiment in my school lab in which we had to identify the given organic compound. In my Lab Manual, it's written:
Take 2 ml of Tollen's Reagent and add a few drops of organic sample. ...
-3
votes
1answer
78 views
Significant figures and accuracy [closed]
A sample was weighed using two different balances. The results were $\pu{(a) 4.929 g and (b) 5.0 g}$. How would the mass of the sample be reported?
Method 1
$$ \text{Average of the values} =\frac{4....
0
votes
1answer
28 views
Effect of reduction potential on particle size of chemically precipitated silver particles [duplicate]
Is there no mathematical relationship between redox potential and particle size saying that an $X$ potential should yield a $Y$ particle size? Right now its general that large redox potential results ...
0
votes
0answers
41 views
Why does a mentos make soda explode? [duplicate]
So if you put a mint mentos in a cup of soda it will explode everywhere. The mint in the mentos makes the soda have a chemical reaction which will then make the soda explode right? Well what would ...
1
vote
0answers
26 views
Why does changing the salt of the salt bridge effect the voltage produced in a galvanic cell?
My experiments results showed that the voltage decreases down $\pu{Group 1}$: $\ce{Cl-}$ salts in the salt bridge. All other variables were kept constant. $\ce{Zn}$ and $\ce{Cu}$ rods were used. ...
1
vote
0answers
34 views
Suggestions for chemistry experiments to do regarding toxic gasses
I'm doing a final project on mustard gas, and need an experiment to conduct. I'm obviously not allowed to make or work with mustard gas, but what else can I do? Any other gas experiments that would be ...
0
votes
1answer
61 views
Solvent for reaction mixture
I'm looking for some suitable solvent for ether cleavage of Guaiacol (o-Methoxyphenol) using aluminium triiodide ($\ce{AlI3}$) with $\ce{DMSO}$. The original paper calls for using hot acetonitrile as ...
0
votes
1answer
37 views
electrochemistry experiment
something strange.
i made an electrochemistry experiment in which i have measured the potential of cell:
Ag, AgCl | (1M)KCl ║ [Fe(CN)6] 3-, [Fe(CN)6] 4- | Pt
with different concentrations of Fe+2/Fe+...
0
votes
2answers
79 views
Is aluminium foil pure aluminium? [closed]
Is aluminium foil pure aluminium? Or does it have other elements in the e.g: tin (Sn) or lead (Pb)? Because when I try to oxidize it through the process of submerging it in water, it doesn't look like ...
1
vote
0answers
20 views
Can Methylene Blue Detect Spoilage in Food?
Initially, there is already a product which is a sensor based on Methylene Blue, which can detect changes in oxygen levels in a packaging. However, as our thesis project, we decided to take on this ...
0
votes
0answers
32 views
How can a DPPH assay to measure antioxidant activity of beta carotene be conducted?
I am currently doing some research regarding beta-carotene. With reference to other sources and their methodoloy for DPPH assay, I conducted my experiment but failed to find any significant peak in ...
16
votes
1answer
3k views
Neutralizing a sulfuric acid spill
From my AP Chem Prep Book:
What should you do if you spill sulfuric acid on the countertop?
A) Neutralize the acid with vinegar.
B) Sprinkle solid NaOH on the spill.
C) Neutralize the acid ...
0
votes
2answers
69 views
Unusual Result in Kinetics Lab
The question: In the lab described below, why did the decolorization reaction described, which should be first order in each of the two reactants, go most slowly when the reactants were most ...
1
vote
0answers
19 views
Extraction Techniques for Organic Compounds from Aqueous Media
I am looking to attempt an extraction of an organic compound that had just been prepared using a Friedel-Crafts acylation. The compound was prepared in MDC (~20 mL in total). After the reaction, the ...
0
votes
0answers
15 views
measuring the pKa of acetic acid in mixtures of water and methanol(changing percentage)
My goal is to measure the pKa of acetic acid in different mixtures of water and methanol, in which the proportion by weight of methanol will be changed. How can I measure the pH of this solution? Is ...
1
vote
1answer
44 views
Is there any aqueous solution (or simple method) to remove trace level of sulfur dioxide/nitrogen monoxide and nitrogen dioxide in a gas stream?
I need to generate pure gas from a gas stream which is free of $\ce{SO2}$/$\ce{NO}$/$\ce{NO2}.$ The air is already pretreated by activated carbon and purafil. However, I can't find any solution for ...
0
votes
1answer
23 views
How to increase volatility? [closed]
Is it possible to put a substance with low volatility into a highly volatile solvent, thus make the original substance also vaporize quickly?
If not, are there anyway to increase it's volatility?
