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.

Filter by
Sorted by
Tagged with
-2
votes
1answer
2k views

What is the titre of a sodium hydroxide-sulfuric acid titration experiment?

So I did for my AS Level exam today a titration experiment, seeing how much sulfuric acid of (I think) about $0.100 - 0.200 \text{ mol dm}^{-3}$, which went in the burette, is needed to react with 0....
2
votes
1answer
1k views

Alternatives to Congo Red?

I require Congo red indicator for an experiment I wish to perform involving dipping a cellulose sponge into an acid and a base. I first want to dye the cellulose sponge with Congo red, and observe ...
4
votes
2answers
5k views

Presumptive test for modafinil?

Given a sample that is probably modafinil plus common fillers, but could be fake, what reagent tests would best determine whether it contains modafinil? Assume a known-good sample for comparison. (...
2
votes
2answers
1k views

Hot and cold air interaction in a sealed environment

What would happen if air heated to 1200 degree's Fahrenheit in a sealed environment was injected with colder air? No specific pressure defined yet just a general idea of potential interaction between ...
6
votes
3answers
3k views

What is the procedure of designing a salt bridge for a galvanic cell?

I'm doing an experiment where I'm measuring the effect of changing the $\ce{Cu^{2+}}$ ion concentration on the voltage in a copper-zinc galvanic cell. I'll be doing at least five trials for each of ...
7
votes
4answers
325 views

Varying potential diffrence between two graphite strips in NaCl solution

I have two identical graphite strips of dimensions 3.5 cm by 1 cm. Both are 3/4 submerged in aqueous $\ce{NaCl}$ solution (0.34 mol/dm$^3$, 2% wt) separated by a distance of 7 cm. I have attached ...
6
votes
1answer
146k views

What is the reaction between oxalic acid and potassium permanganate?

I've already searched online some information about this equation, but everywhere I read, there's also sulfuric acid, which we did not use in the laboratory. We only used potassium permanganate and ...
6
votes
2answers
13k views

Can you create a buffer with a strong acid?

So I was wading through several textbooks yesterday reviewing the concepts of buffers. I found them lot more challenging than I used to. One thing in particular disturbed me: The books and internet ...
4
votes
1answer
3k views

How is the time for a test tube in a centrifuge determined?

I came across some hairy math that's used for analytical centrifugation, mostly for things like determining the sedimentation rate for liquids. However, what I don't understand is how someone ...
5
votes
1answer
995 views

What is a “lagged bath”?

First question, and this is one I've searched for in vain. In the context of setting up cooling baths, I've come across the term "lagged" bath. I cannot extract what this means from any available ...
4
votes
1answer
190 views

Ambiguity in synthesis (crystallization)

A paper says the following, Dichloroglyoxime was prepared by chlorination of glyoxime in 10 % HCl at 0 deg C and crystallized from toluene. When they say "crystallized from toluene" do they ...
5
votes
2answers
1k views

How do you Synthesise a Fatty Acid Amide?

How would you go about synthesising a fatty acid amide, preferably by means of a high-yield reaction. Please provide an explanation that I, as a grade 12 chemistry graduate, could understand. I am ...
2
votes
1answer
3k views

Why should I add lithium bromide to my GPC eluent?

I'm running gel permeation chromatography (GPC) of a polar, uncharged polymer (acrylamide-based) in a polar solvent (dimethylformamide). The literature recommends adding a salt to the eluent; for my ...
4
votes
1answer
791 views

Clathrate Compounds with Quinone

I prepared a compound "$\ce{SO2}$-Quinolclathrate" by dissolving hydroquinone and sodium sulfite with hydrochloric acid in warm water. After this, I tested a little sample of the product on a flame ...
1
vote
3answers
5k views

Looking for a safe exothermic reaction [closed]

Is there an exothermic reaction which produces 1 to 2 minutes of heat at around 175 degrees Fahrenheit, no toxic gasses and is considered to be more or less safe?
2
votes
1answer
121 views

How are crystals formed from a gas?

In crystallization, crystals are formed from liquids by cooling. How can crystals be formed from a gas by cooling?
5
votes
1answer
856 views

What components of safety should be included in a chemistry laboratory experiment conclusion?

The focus of my question here is this: In a laboratory there is a Bunsen burner, a hot plate, hydrochloric acid, and concentrated ammonia. What would you mention about safety precautions? As students ...
4
votes
1answer
4k views

Inherent error in mass and volume?

In one of my chem classes I had to do a lab that involved finding the mass and volume of a substance. I did three trials and for my mass I got 9.3g, 9.3g, and 9.4 g. For my volume, I got 9.7ml, 9....
6
votes
1answer
9k views

Pipetting strong acid with plastic material

Can I pipette concentrated sulfuric acid using a plastic pipette tip? Will either the plastic or the acid be affected?
6
votes
2answers
1k views

Comparison of acids to dissolve phosphates

I am currently reading this German paper on the dissolution of phosphates by acids and chelants. The authors do a "fast-test" of the dissolving power of different acids which goes as follows: For ...
4
votes
1answer
746 views

How to compute the residence time for given flow rate in standard cubic meters?

I'm given a flow rate of a gas mixture of $3\ \mathrm{Nm^3/h}$ in standard cubic meters through a cylinder of length $50\ \mathrm{cm}$ and cross section $70\ \mathrm{cm^2}$, can I compute how long a ...
40
votes
6answers
72k views

How can carbon dioxide be converted into carbon and oxygen?

How can $\ce{CO2}$ be converted into carbon and oxygen? $$\ce{CO2 -> C + O2}$$ Alternatively: $$\ce{CO2 + ? -> C + O2}$$ I'm aware that plants are capable of transforming $\ce{CO2 + H2O}$ to ...
53
votes
4answers
178k views

Why add water first then acid?

From school, I remember a very important rule: first you need to pour the water and then the acid (when you need to mix them) not vice-versa. This is because otherwise the aсid becomes very hot and ...
2
votes
1answer
263 views

How would I neutralize a PEP (Phosphoenolpyruvic) acid?

PEP (Phosphoenolpyruvic acid) is acidic but I need to make it neutral. I need a solution (pH 6-8) of PEP in a final 1 mL volume with a concentration of 100 mM. How would I make this?
12
votes
1answer
3k views

How did Michael Faraday melt Sodium Chloride?

Michael Faraday melted sodium chloride in a silver spoon and ran an electric current through the molten salt, which released chlorine as a gas and left pure sodium behind. Sodium chloride melts at $...
8
votes
3answers
2k views

What is the correct name for this lab technique in crystallization?

Take a glass rod and rub vigorously the wall of the flask, the substance will crystallize out of the solution. Take a fire polished stirring rod and etch (scratch) the glass of your beaker. The small ...
7
votes
1answer
733 views

Test presence of oxygen > 1%

I want to qualitatively test for the presence of oxygen within argon gas. I would like the test to be positive if approx $1\%$ or more is oxygen, but definitely negative if less than $0.1\%$. Anywhere ...
7
votes
1answer
126 views

How do you determine the amount of acrylamide in foods such as baked fries?

There are many food studies which determine the concentration of a substance in a food item. For example, this study determines the concentration of acrylamide in solid foods like fries. By what ...
4
votes
1answer
834 views

How does a Brunauer–Emmett–Teller device function?

The Brunauer–Emmett–Teller (BET) theory is comprehensible. My question is more geared towards what is physically and chemically happening within a BET device to get a reading? How does a BET device ...
8
votes
2answers
357 views

How to translate the mobile phase from thin layer chromatography to column?

I recently was told that once you find a good solvent mixture for separation on thin layer chromatography (TLC), you should only use 10% of the more polar solvent (for silica) when you run your column....
9
votes
3answers
600 views

MacGyvering a sealed tube

Is it possible (advisable?) to make a sealed tube by melting and twisting the end of a borosilicate test tube? One issue that I can think of is that the pressure might be too high if I then proceed to ...
8
votes
1answer
183 views

How to characterize gaseous ethylene that forms as byproduct?

I'm running a reaction that has ethylene gas as a byproduct. I have observed gas evolution as my reaction proceeded and I have other ways of verifying the identity of the main product, but I thought ...
38
votes
5answers
44k views

Choosing the right condenser

What are the advantages and disadvantages of the various types of condensers commonly found in the laboratory? Obviously more intricate pieces of glassware are more costly but assuming they are all ...
7
votes
1answer
1k views

What is the behavior of a Zwitterion during ion exchange chromatography?

We're interested in purifying a protein that has an azide moiety using ion exchange chromatography. Due to its unique structure, the moiety is a Zwitterion with a novel chemical behavior. My question ...
29
votes
2answers
122k views

What do the different grades of chemicals mean?

When purchasing chemicals from Sigma, Fisher, or wherever, there are often -grade's attached to their description like reagent-grade, technical-grade, analytical-grade, or more niche-sounding biotech-...
8
votes
3answers
2k views

13C NMR spectrum only showing solvent

This is my first time taking a $\ce{{}^{13}C-NMR}$ spectrum and while I'm aware the signal to noise ratio is much lower compared to $\ce{{}^{1}H-NMR}$, I didn't realize it was quite this bad. I took a ...
22
votes
4answers
40k views

what kind of suspension liquid should be used with ferrofluid (so it does not stain the glass)

Please take a look at the following video: I am working on a new project, and I need to find whats the best liquid to hold ferrofluid inside the glass (or maybe even plastic) container, so that ...
7
votes
2answers
4k views

How long does it take to run a MS/MS experiment

I am not planning to do these types of experiments but I would like to know the order of magnitude of the time it takes to run an LC-MS/MS experiment. Let's assume that I have the sample prep (protein)...
10
votes
1answer
3k views

What's the difference between precipitate and turbidity?

In many tests for various radicals, a "<color> precipitate" or "<color> turbidity" is mentioned. For example, lead ...
8
votes
2answers
22k views

Why are strong acids and bases not suitable as primary standards?

This is one of the questions with which I have puzzled over, and can arrive at no definite conclusion. Why are strong acids or bases, such as $\ce{H2SO4}$,$\ce{ HNO3}$, $\ce{HCl}$, and $\ce{NaOH}$ not ...
10
votes
2answers
8k views

Gas chromatography/mass spectrometry: Can I use peak ratios and molecular mass to derive quantity?

Can derive the quantity of a substance from a GC/MS report if I know: the ratio to another substance in the data, the quantity of that second substance, and the molecular mass of both substances. ...
10
votes
3answers
2k views

Experimental calculation of solubility product constant

In order to calculate the $K_\mathrm{sp}$ of lead(II) iodide, I mixed $\pu{6.0 mL}$ of $\pu{0.01 M}$ $\ce{Pb(NO3)2}$, $\pu{6.0 mL}$ of $\pu{0.02 M}$ $\ce{KI}$, and $\pu{8.0 mL}$ of water, and a ...
9
votes
6answers
4k views

A quick method for separating liquids?

I'm looking for a way to take 3 separate liquids (liquids which function as paint -- they will all be different colors), put them together into a container, and then rapidly separate them back to ...
24
votes
2answers
2k views

What can I do if I don't get a phase separation between my organic and water phases?

Solvent extraction in a separation funnel is a very common method in preparative organic chemistry. But sometimes you don't get a nice phase separation between the organic and the water phase. What ...