The branch of chemistry concerned with identifying and quantifying the chemical constituents of matter.

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Smith Hieftje correction method

I completely don't understand how this method works. My book says : this method works by the principe of self-absorbtion which occurs by the emitted radiation of hollow cathode lamp when it works on ...
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2answers
14 views

Why are hollow cathode lamps used for atomic absorption spectroscopy?

In 1955, it was proposed that hollow cathode lamps are good emission sources for monochromatic radiation, and thus for atomic absorption spectroscopy (AAS). In looking into the topic, I've read that ...
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30 views

Instrumental methods of analysis

I am taking the instrumental methods of analysis course. Our job is to find the unknown mass of $\ce{Fe}$ which is added, by measuring the absorbance of different solutions with ortho-fenantroline. ...
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30 views

Comparing wt% to at% which is normalized to 100%

I have measured the element composition of a sample using ICP-OES, and reported my results in wt%. A study which has analyzed the same sample types, but with an electron microprobe, has reported their ...
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1answer
35 views

Spectral Peak-Picking in MS Excel

I'm working often with spectral data of various gases, and the bulk of the data analysis is assigning the peaks with maximum signal (y-axis) to frequency (x-axis). Often we have several thousand data ...
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1answer
23 views

Yeast Fermentation with YPD + Apple Juice

I am working on a project for my General Chemistry class. I am trying to compare the EtOH production (and the rate of EtOH production) between seven types of yeast strains by fermenting the YPD ...
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1answer
43 views

How to calculate the required concentration for sodium sulfite to remove oxygen as an oxygen scavenger from a solution?

If I know the amount of oxygen in such a solution, how can I know the required concentration of sodium sulfite to be used and react as oxygen scavenger?
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1answer
30 views

Spins spin coupling on proton NMR for an aldehyde?

On a proton NMR, does the hydrogen in the CHO group cause coupling, or get coupled itself? Specifically, I a considering 2-methylpropanal. I cannot decide whether the H in the aldehyde group would be ...
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1answer
27 views

Detect Polyethylene

How can we detect polyethylene from a distance? The method should be mobile as I am thinking of employing it a mobile robot. I have no idea about it. Any suggestion or external link would be ...
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1answer
33 views

Colorimetric test to measure dissolved oxygen in salt water

Are there any simple colorimetric tests for measuring the dissolved oxygen in salt water, which do not involve titration like in Winkler method ? i.e. Are there any chemical reagents, which when ...
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19 views

Is Polymorphism accompanied with an energy change?

Differential Scanning Colorimetry (DSC) is a technique used to identify Polymorphism by revealing two melting points of a pure crystalline structure. DSC shows a peak associated with the formation ...
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1answer
50 views

How to find pKa given absorbances and pH [closed]

If the absorbance of one of the buffer solutions (pH = 4.623) was 0.319 and the absorbance of the basic solution was 0.625, what is the $\mathrm{p}K_\mathrm{a}$ of the indicator? Include activity ...
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1answer
38 views

Finding is the concentration of H⁺ in a benzoate buffer solution after adding HCl

Q: A buffer with a pH of 4.44 contains 0.21 M of sodium benzoate and 0.12 M of benzoic acid. What is the concentration of $\ce{[H^+]}$ in the solution after the addition of 0.050 mol of $\ce{HCl}$ to ...
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1answer
45 views

What happens if don't use MgCl₂ in buffer solution in Ca²⁺/Mg²⁺ titration?

What happens to a complexometric titration of calcium carbonate (analyte) with $\ce{EDTA}$ (titrant) when no magnesium(II) chloride crystals are added to the buffer ($\ce{NH3/NH4^+ + EDTA}$) solution? ...
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1answer
27 views

Analysis project to conduct [closed]

We have been asked to conduct an analytic project for chemistry. It is important that the project conducted hold social implications and the conclusion achieved help inform people better. Several ...
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0answers
23 views

How do you calculate the effect of adding more acid past the neutralization point? [duplicate]

In titrating a weak acid with a strong base, and given the mole values of each component at the endpoint and the pH there, how do you calculate the pH and species' concentrations after adding an ...
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1answer
36 views

3rd analytical group of cations

If a mixture of Mn$^{2+}$, Zn$^{2+}$, Co$^{2+}$, Ni$^{2+}$ and Al$^{3+}$ salts is dissolved in water, a white dim solution is obtained. I guess that the aluminium and zinc ions hydrolysed and the ...
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1answer
34 views

Finding out the concentration of oxygen in water

I read in a biology course that you can determine the concentration of oxygen in water by adding some $\ce{NaOH}$ and then a small amount of $\ce{MgCl2}$. They say that a dark coloured precipitate is ...
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1answer
49 views

Molarity vs Normality in labeling sulfuric acid

Molarity (M) is defined as moles of solute per liter of solution while Normality (N) is defined as moles of reacting units per liter of solution. Most texts use sulfuric acid as an example to ...
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1answer
46 views

How to determine methane percentage at home?

Suppose I have gas bottle and gas cooker. Suppose I have propane in my bottle and I suspect it is diluted with unknown gas. How can I measure with simple instruments, how many propane I have ...
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1answer
32 views

Purifying washing soda

I bought a box of A&H Washing Soda, the packaging of which implied that it was pure washing soda (sodium carbonate). On dissolving it in osmotically-purified water, however, I found that the ...
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2answers
43 views

How to report pH values?

I have measured the pH in the water-soluble fraction of a powder. I weighed in a certain amount of powder and a certain amount of water, and extracted the water-soluble fraction. I then measured the ...
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1answer
34 views

Testing for the presence of Hexamethylenetetramine / Formaldehyde [duplicate]

I read in Russian popular articles that it is allowed to preserve herring/fish with Hexamethylenetetramine in Europe. Since Soviet times, I like to buy salty herring and marinade it with Vinegar. The ...
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1answer
55 views

How to calculate the oxidation state and the number of equivalents oxidized with YBa₂Cu₃O₇

I've hit some trouble with these calculations and need help sorting out confusion. In the lab we synthesized $\ce{YBa2Cu3O7}$, per the lab manual $\ce{Y, Ba, O}$ have the usual charges of +3, +2, and ...
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1answer
34 views

Why do electrons not get paired up in [Fe(H2O)5NO]2+?

The magnetic moment of [Fe(H2O)5NO]2+ is 3.87 Bohr magneton, which implies there are 3 unpaired electrons. Since iron is in +1 oxidation state (due to charge transfer with nitrosyl group), it's ...
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1answer
22 views

Is it possible to separate out (MgxCu1-x)2(CO3)(OH)2 into simply (MgxCu1-x)(CO3)?

Good afternoon, Here is the problem I am stuck with, in particular just the first part of it. I have calculated the moles (4.492 x 10-3 mol) and I am quizzed with regards to the equation that occurs. ...
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1answer
67 views

Calibration Curve Error Propagation

I am using ED-XRF for geochemical analysis for a geology dissertation. The ED-XRF provides a ppm reading for elements and a 2sigma error, for example 472 +- 5.11ppm Sr. An example calibration ...
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19 views

The Workings of Pulse-Height Discrimination

Pulse-height discrimination is a common technique to filter out unwanted background signals from the analytical signals. But how exactly does it work? The analytical signals are not continuously ...
3
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1answer
98 views

Analytical Chemistry predicting the order of elution of compounds in a reverse phase HPLC

Predict the order of elution for a mixture containing caffeine and benzoic acid, using a reverse phase HPLC. Explain your answer. My try Since benzoic acid is more acidic that caffeine, which means ...
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1answer
138 views

Questions on reactions during salt analysis [closed]

I have two questions: What is the reaction between Diphenylamine with Nitrite compound during Nitrite test during anion analysis DIPHENYLAMINE - $\ce{(C_6H_5)_2NH}$ NITRITE - $\ce{NO_2^-}$ What is ...
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1answer
379 views

Would there be a difference if deuterium is embedded instead of protium (regular hydrogen) in acids?

So instead of regular hydrogen, it would be a deuterium (still a Hydrogen). For example, instead of $\ce{HCl}$ it would be $\ce{DCl}$ where D is a deuterium.
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1answer
88 views

What kind of compound absorption the 365nm UV light on TLC [closed]

What kind of compound absorption the 365nm UV light? compounds that has benzene ring or conjugated pi bond, make a fluorescence on 254 nm UV on TLC. what kind of moiety(functional group) make ...
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1answer
89 views

what is the white fuzz left behind on basement floor after puddle evaporated

My basement is quite dry (knock on wood!). Recently I brought into the basement for the winter a table from outside. The table had some ice stuck to it which I couldn't remove, so I simply let it ...
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1answer
49 views

Mathematical Statistics and Chemistry

I'm currently working towards a major in both chemistry and mathematical statistics as a part of my science degree, and I got to wondering: How will these two go hand in hand and help each other? ...
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73 views

When will the mass of the reactant increase while being heated up?

There is some kind of system which measures the mass of an unknown solid substance as it heats up, of course for the elemental analysis of the very substance. (didn't really find a good name for that ...
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52 views

Echelle Monochromators

"For any given order, the wavelength dispersion is approximately linear. but the dispersion is relatively small at lower orders or higher wavelengths." As you can see, wavelength dispersion and ...
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1answer
47 views

How does light get refracted through five lenses in a component of a spectrometer? [closed]

Question three in my Pre-lab questions for my Physical Chemistry practical is causing me problems. If a parallel beam of light hits the first lens with focal length 2F it will cause the light to ...
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24 views

Cation exchange capacity via IR spectroscopy? Is it as good as barium exchange? What is the intutition on how it works?

Cation exchange capacity is often regarded as the single best summary statistic for soil fertility. Years ago, I learned how to measure it myself, in a soil lab. I used compulsive barium exchange, ...
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2answers
90 views

UV-Vis Spectra: Multiple peaks for one component

I am working on a project in my lab, and we are analyzing capsaicin using HPLC. I am trying to find an appropriate wavelength for the HPLC using a UV-Vis spectrometer. When analyzing the pure ...
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2answers
223 views

Buffer Solution - Sodium Benzoate

A buffer with a pH of $\mathrm{4.79}$ contains $\mathrm{ 0.39\ M}$ of sodium benzoate and $\mathrm{0.10\ M}$ of benzoic acid. What is the concentration of $\mathrm{[\ce{H} ]}$ in the solution after ...
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24 views

Preparing standards for ion chromatography by weighing in amounts: correct for density?

Let's say we want to extract the water solvable part of an unknown powder, and analyse for anions. We put the powder in a tube with a filter at the bottom, add 10 mL water, and let the water run ...
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0answers
25 views

How report metal amounts as amount of their respective metal oxides?

I have performed an element analysis, and I I have calculated the amount of each metal in my sample, given in milligrams. Let's say I weighed in 10 mg of the powder. I want to see how much of that I ...
3
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1answer
812 views

Definition of major, minor, and trace elements in analytical chemistry

What is the definition of major, minor, and trace elements in a sample? I am unable to find this anywhere on the internet. Is it something like: Major elements are those > 0.1 % Minor elements are ...
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1answer
43 views

ICP-OES data treatment: correct for dilution and inweight, the units

Let's say the ICP-OES software gives me a concentration of 186,49 ppm (mg/L) of Mn. I diluted the acid digested sample to 14.2 mL. I weighed in 10.17 mg of the powder I analyzed. I need to calculate ...
3
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2answers
412 views

Precautions and tips for Qualitative Inorganic Analysis of Coins

I'm a highschool student and as part of an investigatory project, I have decided to analyse which metals are present in our everyday coins. I chose this because in my previous academic year, I had ...
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1answer
68 views

What do chemical constituent measurement units 'g%g' and 'µg g⁻¹' mean?

I'm trying to understand the following data being presented in this paper measuring the mineral content of the Cannabis sativa plant (leaves and inflorescences): I need to interpret these data ...
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1answer
307 views

How can I deduce the linearity of XeF2 from the IR spectrum?

The vibrational modes of $\ce{XeF2}$ are at $555$, $515$, and $213~\mathrm{cm^{-1}}$ but only two are IR active. Explain why this is consistent with $\ce{XeF2}$ having a linear structure. From what ...
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1answer
145 views

How to calculate the detection limit?

I am having trouble figuring out how to calculate the detection limit. Here is the question: You and your friend working in a different lab have been given an unknown water sample that contains ...
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1answer
107 views

how to measure dissolved oxygen?

How do you measure dissolved oxygen reliably in a culture of cells? This page has info on one sensor: http://water.me.vccs.edu/concepts/domeasure.html how would you know that this sensor is working - ...
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2answers
203 views

How do I determine the mass percent of Barium nitrate and Sodium acetate in an original unknown solution

I am given $20 \mathrm {mL}$ of the unknown mixture of Barium Nitrate and Sodium Acetate dissolved in water. I am given the total mass of the two solids before they were put into the mixture. I am ...