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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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7
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2answers
2k views

Why a specific temperature for value of 1 calorie?

Everything in chemistry often comes with a strong reason and facts behind it, but I stuck in definition of $1$ calorie. My reference book define one calorie as amount of heat required to raise the ...
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1answer
2k views

Why does sodium sulfate initially harden instead of dissolving?

I was recently drying a product by passing it through a bed of sodium sulfate in a fritted glass Buchner funnel. Once I had finished up working my reaction, in an ill-advised attempt to clean up, I ...
7
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2answers
28k views

Why are NaCl and NaBr not soluble, whereas NaI is soluble in acetone (in the Finkelstein reaction)?

My book states that: Finkelstein reaction is particularly useful for preparing iodoalkanes. The iodoalkanes are obtained by heating chloro or bromoalkanes with a concentrated solution of sodium ...
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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
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1answer
134 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 ...
7
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1answer
154 views

What is the standard way of reporting/interpreting measurement uncertainty in scientific publications?

As an undergraduate student I was often told in lab classes to report every single measured or calculated quantity with its associated uncertainty in lab classes, in the form $(10.1 \pm 0.1 )~\mathrm{...
7
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1answer
83 views

Have Ionic Liquids been used to refine aluminum on an industrial scale?

Ionic liquids have been shown capable of reducing aluminum trichloride to solid aluminum at 3kw-hrs per kg of Al(s) produced instead of the current ~15kw-hr/kg. However, this would seem to neglect the ...
7
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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 ...
7
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2answers
8k views

How to calculate percent error for absolute zero?

In chemistry lab, we did an experiment with water of various temperatures to extrapolate a value for absolute zero based on experimental pressure values for water at different temperatures. Naturally, ...
7
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1answer
687 views

Easy-to-do experiments that clearly show outstanding properties of graphene

By chance, we received some monolayer graphene sheets (20 cm x 20 cm) and mixed coper-graphene wires for free at our university. I would like to prepare some very-easy-to-do experiments for the ...
7
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1answer
865 views

Mixing naphthalene, formaldehyde and sulfuric acid (Marquis reagent + naphthalene)

Excuse me if this a dumb question but it has haunted me for years. Back in my old school days I mixed naphthalene, formaldehyde and sulfuric acid in a mad attempt to make $\mbox{2-Methoxynaphthalene}$...
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3answers
19k views

H2SO4 with ethanoic acid reaction?

Earlier today I was preparing an ester (propyl ethanoate) and I noticed that instead of putting the propanol, ethanoic acid and $\ce{H2SO4}$ in the test tube and warming it (taking time and external ...
7
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1answer
115 views

Is it possible to produce sulfuric acid at large scale by oxidizing and hydrating pyrite?

I was reading The Knowledge by Lewis Dartnell, which is a book about recreating our technology from scratch should we experience a civilization-ending apocalypse. The author thinks that acquiring ...
7
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1answer
288 views

Grignard reaction on electron-poor benzyl bromides

I am trying to prepare a Grignard reagent from 4-nitrobenzyl bromide but the reaction just doesn't work. My conditions are: 10 mL of THF (anhydrous); 7.04 mmol of 4-nitrobenzyl bromide; 7.04 mmol of ...
7
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1answer
138 views

Why do people consider caffeine ineffective after its half-life?

Assuming you take $\pu{200mg}$ of caffeine, it's half life is roughly 6 hours. So after 6 hours there should still be $\pu{100mg}$ of caffeine in your body. Then why is it generally said that after ...
7
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4answers
387 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 ...
7
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1answer
902 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 ...
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0answers
143 views

Distilling milligram quantities of oil like it's late 1970s

In a currently retracted* manuscript by Tomas Hudlicky [1, Retraction Watch] the following has been noted: Fifty years ago professors took an active part in all laboratory instructions and they ...
7
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1answer
716 views

The open circuit voltage of a battery: Does it decrease with increase in pH of electrolyte while the voltage across a load increase?

Why does the open circuit voltage of a battery decrease with increase in $\mathrm{pH}$ of electrolyte, but the voltage across a load increase? I tested a cell which had aluminum sulfate as its anode ...
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0answers
1k views

Tables/database/literature of specific or optical rotation

I'm looking for a comprehensive reference of experimental specific rotation or optical rotation data. It can be a published literature review, a free web database with API access or one that permits ...
7
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0answers
495 views

Does phosphoric acid remove stainless steel electropolished layer?

Electropolished stainless steel has a high corrosion resistance due to the oxide film that is created during electropolishing. The film mainly consist of chromium(III) oxide. Phosphoric acid is ...
7
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0answers
55 views

Linear PEI Solution Making

I'm making a solution with linear poly(ethyleneimine) $\ce{[CH2CH2NH]_{n}}$. The bottle indicates that the substance is hygroscopic and must be dealt with under inert gas. Is this really necessary? ...
6
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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 ...
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3answers
1k views

How to control current and voltage in electrolysis

I am doing an experiment that aims to determine if the rate of electroplating changes with the temperature. I am using a copper rod, a solution of copper(II) ions and a neutral rod to be coated. I ...
6
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2answers
423 views

How do we identify the molecular formula from the empirical formula of a completely unknown substance? [closed]

Suppose you are given a sample of new (undiscovered) hydrocarbon with 600/7% $\ce{C}$ and 100/7% $\ce{H}$. (From combustion or any other method) We can find the empirical formula to be CH. Then how ...
6
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2answers
706 views

How do I heat my borosilicate reflux column?

I am gonna use a ceramic tape heater, but cannot wrap it around evenly. Is the glass column gonna be okay? I am running some tests on plastic pyrolysis. I am using the reflux condenser to make the ...
6
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2answers
8k views

Why is a volumetric flask shaped the way it is?

A volumetric flask does not look like an Erlenmeyer flask, but has more of a pear shape. Is it just to distinguish more easily between them while they are on the shelf?
6
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2answers
170k 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
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1answer
3k views

What makes R-MgX a more reactive Grignard reagent than R-Cu?

What makes $\ce{R-MgX}$ a more reactive Grignard reagent than $\ce{R-Cu}$? Has it to do with solvation, bond enthalpy, electronegativity?
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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:...
6
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2answers
328 views

Scientific Reason for Salt Solution Gaining Volume

A little background to this question: my mom placed a glass with salt and enough water to just cover the salt in a room to "absorb negative energy" out of the room at her office. It obviously "worked"....
6
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1answer
14k 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
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1answer
5k views

Why would rinsing the flask with acid in this experiment affect its accuracy?

The following question is #21 from this test form (PDF link): The apparatus in Figure 4 was set up to measure the time taken for $\pu{20.0 cm3}$ of sodium thiosulfate solution to react with $\pu{5.0 ...
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2answers
1k views

How full is a gas cylinder?

There are 7 different gas cylinders filled with: nitrogen oxygen air methane hydrogen sulfide carbon dioxide sulfur dioxide How do I determine how much of the respective gases is left? Nitrogen ...
6
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2answers
122 views

Removing sodium borate for the test proving thiocyanate ions

I've just learned that when carrying out the identification test for thiocyanate ions borax can induce a false positive and therefore needs to be removed. I couldn't find the answer on google so I'm ...
6
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2answers
2k views

Producing sulphur dioxide for using in a reaction

I am doing an investigatory project on studying the coloured reactions of d-block and f-block elements. I have included two reactions that require sulphur dioxide as a part of my study. $$\ce{5SO2 ...
6
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1answer
276 views

Can gas be made to block radiation better?

Can any gas block radiation? I ask this because I would like to know if the properties of any gas element would chemically react differently with radiation from adding an electrical current. This ...
6
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1answer
2k views

Was Wöhler’s urea synthesis carried out with or without oxygen?

I learnt and was very impressed by the urea synthesis by Wöhler in 1828. The reaction was the heating of ammonium cyanate. One of my textbooks in the library said that ammonium cyanate was heated ‘in ...
6
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1answer
17k views

HPLC: peak area vs concentration

Many text books say that there is a proportionality between the peak area of the chromatogram and the concentration. However, in my opinion, there should be a proportionality between the concentration ...
6
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4answers
468 views

How do I create a concentrated solution of singlet oxygen (in the dark)?

Without appealing to reactions that require photons / light, how do chemists achieve a very high concentration of continually produced, though quite short lived, singlet oxygen in aqueous solution (i....
6
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1answer
170 views

Analysis of cations using sodium thiosulphate

A question in an exam was as follows:[1] How many of the following salts are first soluble in $\ce{Na2S2O3}$ solution, followed by the formation of a white precipitate and finally the precipitate ...
6
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1answer
353 views

Why is the Jacobsen's catalyst with tert-Butyl groups a better catalyst for epoxidation?

In an experiment I synthesised the below Jacobsen's catalst: I used it to create styrene oxide through epoxidation. Chiral GC analysis showed that the enantiometric excess was lower compared to using ...
6
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2answers
699 views

What does radiofrequency really do in NMR & MRI?

In NMR, the protons’ frequencies are affected by the magnet which makes them precess around its magnetic field so now all protons will have different frequencies according to their environment ...
6
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1answer
226 views

Types of argon gas regulator? [closed]

I have a high pressure bottle of argon gas (99.98 %) that I need to use in an experiment. The problem is that the regulator I have is a generic type that is seemingly optimized for high flow rates (...
6
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2answers
404 views

How can I turn LPG from liquid to gas?

I am working on a personal project that involves a balloon filled with liquefied petroleum gas (LPG) at a pressure of $\pu{4 - 5 bar}$, and I need some kind of a device/filter that would convert it to ...
6
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1answer
683 views

Can you synthesize phenol from salicyladehyde?

Can you synthesize phenol from salicyladehyde? Well for starters I know that salicyladehyde can be obtained from phenol through Reimer–Tiemann reaction but I was wondering if the reverse was possible.
6
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2answers
7k views

What are the reaction products of sulfur and potassium nitrate?

YouTube shows videos of dropping a piece of elemental sulfur into molten potassium nitrate and applying additional heat to accelerate the process. A white precipitate falls out to the bottom. There is ...
6
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1answer
730 views

How does aluminium amalgam work as a reducing agent?

I can't seem to find much information on this topic but how does aluminium amalgam work as a reducing agent? Could it be used to deoxygenate a carboxylic acid or amino acid to the corresponding ...
6
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2answers
175 views

How dangerous are these soil organic carbon digestion methods?

I have several ground up soil samples that I need to get fractions from. The fractions are based on the Century Soil Model. Briefly, the fractions relate to the approximate time frame it takes for an ...
6
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1answer
31k views

Effect of dillution on titration

When we are titrating acid/base using ph meter we add distilled water to immerse the ph electrode. Won't this affect the concentration of the acid/base: I mean isn't this dillution. Won't this ...

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