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.

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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 ...
40
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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 ...
38
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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 ...
34
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4answers
8k views

How are poisons discovered? Does someone have to die/be poisoned from it first?

How are poisons discovered? Does someone have to die/be poisoned from it first? Or are there other ways of discovering the harmfulness of a substance? Perhaps everything is tested on other animals ...
30
votes
3answers
76k views

Chemistry behind Gale's coffee maker in Breaking Bad

Is there a scientific basis for the coffee making equipment which Gale Boetticher describes in Breaking Bad? He talks about maintaining the right conditions for bringing out the coffee flavor without ...
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-...
24
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3answers
3k views

How do they ensure there is one electron on an oil drop in Millikan's oil drop experiment?

Since air is ionized using X-rays, in the 'observation chamber', there must be several electrons in the chamber, so the oil drops are exposed to several electrons so it seems intuitive that a single ...
24
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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 ...
23
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1answer
2k views

How can an inexperienced chemist determine the chemical structure of a molecule?

I'm a fairly inexperienced, but nonetheless interested chemist, currently planning a small project for the coming summer: I want to isolate an unknown chemical from a plant and determine it's chemical ...
22
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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 ...
22
votes
3answers
2k views

How was it concluded that the H3O+ rather than H+ is the “acid” ion?

I suspect that initially, scientists believed that the acid ion was $\ce{H^+}$ since $\ce{H2}$ is released through electrolysis, right? But what experiment was done to change the standpoint to assume ...
22
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1answer
646 views

Interlocked cyclic compounds

Being new to chemistry, there may ought to be some properties I couldn't understand fully. One of them being cyclic compounds. One particular question about this is, whether these cyclic compounds, ...
21
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2answers
3k views

Storing hydrofluoric acid before the invention of plastics

The first person to synthesize hydrofluoric acid in large quantities was Carl Wilhelm Scheele in 1771. This acid is known for its ability to corrode glass and metals. What materials were the ...
20
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2answers
7k views

Hottest region of Bunsen flame

Since region 1 is closer to the source, I presume it to be the hottest as complete combustion takes place there. Also, this is the part where the gas mixture(responsible for flame) reacts with oxygen ...
20
votes
1answer
263 views

Is it possible create crystalline solvate of electrons?

Okay, I know that this reads ridiculous insane, but one can obtain solvated electrons by adding sodium metal to liquid ammonia solution. The chemical reaction as written in my inorganic chemistry ...
19
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1answer
10k views

Brown stains on skin after working with Tollens' reagent

I was working in the lab preparing Tollens’ reagent. When I came back home, I observed that my fingertips were brown, and I tried to wash it with soap several times but it didn't work. It has been a ...
19
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2answers
2k views

Does ultrasonic bath cleaning damage laboratory volumetric glassware calibration?

As an analytical chemist, I'm always ensuring my glassware is thoroughly clean before I start an analysis. However, my supervisor always states that using ultrasonic bath to clean volumetric glassware ...
19
votes
3answers
942 views

Quantitative expression for steric hindrance

Steric hinderance is a major component in determining the feasibility and the rate of a chemical reaction. Wouldn't it be useful to measure it quantitatively then? This would make it easier to compare ...
18
votes
2answers
7k views

What exactly happened when I added KOH to hydrogen peroxide?

I recently added a potassium hydroxide, $\ce{KOH}$, pellet to a small droplet of hydrogen peroxide (30 %), $\ce{H2O2}$. You could clearly see the potassium hydroxide dissolving in the droplet when ...
18
votes
1answer
338 views

What is Q-carbon? Does it exist?

Glowing press releases and news articles in 2015 proclaimed a new allotrope of carbon. However, even the journal article is light on chemical detail (e.g. no structural formula). What is its bond ...
17
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5answers
3k views

Why isn't pressure filtration popular compared to vacuum filtration?

I want to build a DIY vacuum filtration apparatus with a bike pump but it's very difficult to find one the could be easily converted into a vacuum pump. This prompted an idea to simply build a reverse ...
17
votes
1answer
2k views

What's this glassware?

Can anybody tell me what this glassware with a stem, bulb and long tube is?
17
votes
1answer
1k views

Conventional heating compared to microwave heating of chemical reactions

In order to try to increase yield of my cross-metathesis, it was suggested to carry out the reaction in the microwave (a lab microwave, not a kitchen microwave). The rationale for this was that ...
17
votes
2answers
16k views

Why is a theoretical titration curve higher than a practical one?

I'm currently in high school and I did two titrations. The first one is a titration of $10.0~\mathrm{mL}$ $0.1~\mathrm{M}$ $\ce{HCl}$ with $x~\mathrm{mL}$ $\ce{NaOH}$. I obtained the following ...
16
votes
1answer
362 views

Why do some solvents bubble more than others when boiling?

This question about boiling milk reminded me of my everyday lab work at the rotavap: Some solvents and solutes are feared for the intense bubbling they create while the solution is boiling — be it at ...
16
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1answer
5k views

Failed synthesis of aspirin due to excess sulfuric acid

Last week, I tried synthesizing acetylsalicylic acid - the reaction is shown below - using $\ce{H2SO4}$ as a catalyst. However, as the title suggests the synthesis failed as I used too much $\ce{H2SO4}...
15
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9answers
8k views

How can 30 ml of water be heated in less than 10 seconds?

How is it possible to heat a tiny amount (30 ml)[1] of water to a high enough temperature to make a coffee, in less than 10 seconds and possibly instantly? Most heaters that I know of heat water ...
15
votes
1answer
1k views

Using a gas stove instead of Bunsen burner for a flame test?

In all chemistry labs we use the Bunsen burner. What's the difference between it and a good old gas stove used in home? Can the stove also be used to get positive flame tests for some cations (like $\...
15
votes
2answers
1k views

Are PTFE stir bars resistant to all lab solvents?

It seems like glass-coated stir bars are a specialty item. Standard stir bars are coated in PTFE. Is PTFE resistant to all typical lab solvents? Or is there a reference to check to ensure it is ...
15
votes
1answer
720 views

Byproducts in Indigo Synthesis?

I have been messing around with making Indigo dye while waiting for bacteria to grow. I have been following the Baeyer-Drewson method. Basically, you mix nitrobenzaldehyde with an acetone water mix ...
14
votes
5answers
8k views

Does increasing concentration of copper sulfate decrease or increase its conductivity?

I am a high school student and for my chemistry lab, I did an electrolyis experiment on how the changing concentration of electrolyte (copper sulfate) will change the rate at which the copper is ...
13
votes
2answers
3k views

Any substance too poisonous to measure an LD50?

A recent question on poisons was answered in part by bringing up the concept of $\pu{LD_{50}}$ and animal testing and so on; none of that was new to me, but it did bring to mind a question I don’t ...
13
votes
3answers
8k views

Why isn't dry CaCl₂ used to dry HCl gas instead of concentrated sulfuric acid?

In our chemistry books, it is said that concentrated sulphuric acid is used to dry $\ce{HCl}$ gas. But, concentrated sulphuric acid is a strong oxidising agent so, why isn't $\ce{HCl}$ gas oxidised ...
13
votes
1answer
200 views

How many particles are necessary to observe a well-defined state of matter?

The three ordinary states of matter $-$ solid, liquid, gas $-$ can usually be distinguished by a function of the strength of interparticular forces and distance. A shorter distance and a stronger ...
12
votes
3answers
28k views

Differentiation between zinc, aluminium, and magnesium ions in solution

If I have three aqueous ionic solutions in which I know that the cation is $\ce{Al^3+}$, $\ce{Mg^2+}$, or $\ce{Zn^2+}$, how do I find out which is which? I was thinking to add $\ce{OH-}$ in the form ...
12
votes
2answers
3k views

Why were elements discovered “out of order” after 1950?

I'm referring to the fact that there is one element that corresponds to one proton in an atom, a second that corresponds to two protons, up to, I believe, an element with 115 protons. These elements ...
12
votes
4answers
15k views

How pure NaCl is typical table salt? How is it purified?

How pure $\ce{NaCl}$ is typical table salt? Is it pure enough for research-level experiments in chemistry? How is $\ce{NaCl}$ purified if need to be?
12
votes
1answer
15k views

Color changes of a solution of acetone and sodium hydroxide

I have put acetone and sodium hydroxide solution (approximately $\pu{1M}~ \ce{NaOH}$) in a beaker and didn't see any colour change for a day (actually, it was transparent, no colour). After almost 2 ...
12
votes
2answers
2k views

In which country is it allowed to practice non-clandestine amateur chemistry? [closed]

I travel a bit so am flexible where I live, and have taken a recent interest in chemistry to try to gain an understanding of physical reality. I find learning from textbooks to be good, but want to ...
12
votes
3answers
7k views

How to remove a stuck stopper from a flask?

How do I remove a stopper that has been stuck in the neck of a 100 mL round bottom flask since I forgot to wipe the neck of the flask. A salt was formed in the 100 mL flask and the stopper ...
12
votes
2answers
11k views

Where's my experimental error coming from?

I’m teaching chemistry to a home-ed 15 year old. Occasionally we do some practical work, since I believe very strongly that physical science learning should have some real lab work to bring it alive, ...
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 $...
12
votes
1answer
97 views

High temperature bath chemicals

I have an electric mantle that I want to bathe reaction vessels at temperatures up to $\mathrm{750^{\circ}C}$. Obviously that rules out oils. What substances are used as bath media at such ...
12
votes
1answer
774 views

What are the practical differences between the various DMSO oxidations (Swern, etc.)?

Recently, I was reading a paper about a total synthesis of (+)-rubriflordilactone A (the article is open access: Angew. Chem. Int. Ed. 2015, 54 (43), 12618–12621). In two different steps where an ...
12
votes
0answers
225 views

Why is Diiron nonacarbonyl so exceptional?

My textbooks says: With exception of $\ce{Fe2(CO)9}$, all other metal carbonyls are soluble in hydrocarbon solvents. Weller, M.; Overton, T.; Rourke, J.; Armstrong, F. Inorganic Chemistry, 6th ed. ...
11
votes
1answer
2k views

What is the role of ammonium chloride in the workup of a Grignard reaction?

In the following Grignard reaction, why is aqueous ammonium chloride used to get to the products? I don't see how it participated in or modified the reaction from what is normally expected.
11
votes
3answers
2k views

How to check if azobisisobutyronitrile (AIBN) is still active?

I will have some samples of azobisisobutyronitrile and I want to perform Barton-McCombie reaction. The problem is that the reagent is quite old and I need to know whether it has not decomposed. Do ...
11
votes
2answers
6k views

Proper use of vacuum pump during vacuum distillation

I am preparing to do a vacuum distillation and am unsure exactly how to manage the vacuum. The vacuum pump I have is a two-stage rotary vane pump which is capable of 250 microns or lower. It has a ...
11
votes
1answer
831 views

What exactly is the Horwitz equation?

During a laboratory exercise in a course on analytical chemistry, we were asked to calculate the $z$-score. $$z=\frac{X_{\text{lab}}-X_{\text{cons}}}{S_{\text{target}}}$$ where $X_{\text{...
11
votes
2answers
239 views

Dissolving metal reductions

Could reduction of an organic compound by reacting it with sodium dissolved in $\ce{NH3}$ still proceed if a metal such as aluminium were used instead of sodium? I'm not sure about the aluminium amine ...