Questions tagged [analytical-chemistry]

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

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5 views

uv-spectrophotometer analytical method for doxycycline hyclate and tylosin tartrate powder

I have try to detect tylosin tartrate from the mixer of doxycycline hyclate using 0.01 M Hcl as solvent at 290 nm the method fail only specificity was good any method ,suggestion and help please
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1answer
22 views

Solubility and wetting of substances in water

We have seen that, when we pour salt in water then it gets dissolved, that means it is soluble in water. But when we pour sand into water then it doesn't dissolve in water, that means it is insoluble, ...
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1answer
32 views

What causes the differences in price in home testing kits for lead in water? [closed]

The price differences between home testing kits to test tap-water for lead are huge. 20 dollar will either buy 1 test kit or 100 test strips. Both are intended to test drinking-water safety. What ...
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17 views

Mass percent of FeO and Fe2O3 [closed]

A mixture of FeO and Fe2O3 is reacted with acidified KMnO4 solution (0.2278M and 100ml of which was used). The solution then was treated with zinc dust which converted all the Fe+3 to Fe+2 ion . This ...
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12 views

Extraction of Chitosan

Does the temperature and duration during oven drying will affect the chemical properties and the quality of the chitosan that will be yield after deacetylation? Any help is highly appreciated. Thank ...
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1answer
62 views

Is it safe to touch salts given to you for analysis? [closed]

In our chemistry practical paper (High school level), Inorganic salt analysis is one of the questions asked. We are given a petri dish with a sample of salt and are asked to find the cation and anion ...
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25 views

Risks of using organic mercury compounds in analytical chemistry

I'm interested in speciation analysis. Hearing of fatal accidents with organic mercury compounds made me wonder about the risks for the analytical chemist trying to determine Hg species in foodstuff. ...
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14 views

Calibration approaches that generally involved plotting signal vs. concentration [closed]

I am hoping to find three approaches to calibration that use the general principal of plotting signal vs concentration. I understand the basic principal of an external calibration but this is just one ...
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16 views

How to account for the common ion effect on osmolarity quantitatively?

In adjusting the osmolarity of a solution of Benzalknonium Cl, Disodium Editate, and Disodium borate/boric acid buffer to be isotonic (about 290 mOsm), the addition of NaCl showed unexpected behavior, ...
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2answers
64 views

What is the principle of RP-HPLC? [duplicate]

Is the following statement the correct way to explain principle of RP-HPLC? It works on the principle of hydrophobic interactions hence the more nonpolar the material is, the longer it will be ...
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7 views

How should this DPPH assay be carried out? [duplicate]

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 ...
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29 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 ...
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22 views

Ideal characterization technique to study behavior of heated metal nitrates

I have 3-4 metal nitrates as precursors for my coprecipitation reaction. I need to study the behavior of each individual nitrate and also of various combinations at 60 degrees Celsius, which is my ...
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LIF spectrum with laser-coupled levels lines as the strongest

Why, if I excited the OH molecule Q-branch transition, my LIF spectrum (recorded during and after the laser pulse) does not result in only Q line being the most prominent, but also P and R lines with $...
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1answer
45 views

Is it possible to obtain the amount of air required for a combustion analysis?

I'm not very sure if the required amount of oxygen (I assume) can be found by only knowing the amounts of the produced subtances after a combustion. To illustrate this I found this problem: $1.14\,...
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58 views

Conditions for choosing quantifying and qualifying ion in LC-MS/MS

In my PhD-work, we are trying to develop LC-MS/MS methods for targeted analysis. Usually, I determine my quantifying ion/fragment based on a few different criteria: If there is a 13C internal ...
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1answer
46 views

Why is high molar molar mass a requirement of good primary standards for volumetric analysis? [closed]

I have been taught that using primary standards with a relatively high molar mass will reduce the error between the equivalence point and the end point during titration. However, I am unsure as to why ...
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49 views

Separation and qualitative identification of cations

A liquid problem may contain the following cations: $\ce{Pb^{2+}}$, $\ce{Cr^{3+}}$, $\ce{Fe^{2+}}$, $\ce{Ca^{2+}}$, $\ce{Fe^{3+}}$, $\ce{Ag^{+}}$, $\ce{Au^{3+}}$, $\ce{Co^{2+}}$. I need to devise a ...
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Electron Ionization and the Franck-Condon Diagram: vibrationally excited and vibrationally ground states

I am currently studying Mass Spectrometry: A Textbook, third edition, by Jürgen H. Gross. On page 41, the author says the following: As explained by the Franck-Condon diagram, hardly any molecular ...
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1answer
112 views

Can 2‐chloropropane and acetyl chloride give the iodoform test?

Can $\ce{CH3-CHCl-CH3}$ and $\ce{CH3COCl}$ give the iodoform test? I thought $\ce{CH3COCl}$ having the keto-methyl group would show the iodoform test, while $\ce{CH3-CHCl-CH3}$ will not since it's ...
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137 views

Inflection point, slope, and equivalence point in a titration

My textbook, Harris 7th Edition Quantitative Chemical Analysis, says: In titrations involving 1:1 stoichiometry of reactants, the equivalence point is the steepest point of the titration curve. ...
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3answers
91 views

How to simplify these system of equilibrium equations

What is the pH when $0.025$ mol $\ce{NiCl2}$ is added to $\pu{1.00 L}$ of a $\pu{0.100 M}$ solution of $\ce{HCN}$, if the formation constant for $\ce{Ni(CN)4^2-}$ is $K_f=\pu{1.0e22}$, and the $K_a$ ...
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1answer
33 views

What am I assuming when I make this approximation?

Suppose you dissolve $\ce{AgBr}$ in a $1$ litre solution of M molar $\ce{Na2S2O3}$. What is the solubility of $\ce{AgBr}$? I am given that the $\beta_2$ of $\ce{Ag(S2O3)2^3-}$ is $2.8*10^{13}$, and ...
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42 views

How is the pH scale constructed? [closed]

How is the pH scale constructed , I mean the strength of an acid is determined by its pKa value and this one can be determined in different solvents if water doesn't suits it but how do you determine ...
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2answers
375 views

How does one tell (or conclude) if a substance is carcinogenic?

It's common to read statements like: Tetrachloroethene ($\ce{CCl2=CCl2}$) was earlier used as a solvent for dry cleaning, but since it contaminated ground water and is a suspected carcinogen, ...
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1answer
35 views

A “function of proportionality” in a rate law [closed]

I am currently studying rate laws and the determination of the order of a reaction. So first-order reactions remind me of linear functions $f(x)=kx$ while second-order reactions remind me of quadratic ...
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1answer
43 views

Flame test for copper salts

I have read from sources here, here and even in my textbook that Copper (specifically $\ce{CuCl2}$ ) burns with a bluish green flame. All the sources mention that this is due to electron excitation ...
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3answers
155 views

I have a solution of citric acid, tartaric acid, water and glucose. How do I find the concentration of the citric acid present in the solution?

If I try to find the concentration of citric acid through back titration or reverse titration, the base I would use, like NaOH, would react with both acids to form sodium citrate and sodium tartrate, ...
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1answer
40 views

How are atomic masses determined? [closed]

The atomic mass (ma) is the mass of 1 atom of an element. Elements have isotopes. Therefore, there must be an atomic mass (ma) associated with each isotope of an element. How do we know the atomic ...
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184 views

Is chromate a suitable indicator for the titration of Ag⁺ with Cl⁻?

To titrate $\ce{Cl-}$ with $\ce{Ag+}$ we use chromate $\ce{CrO4^2-}$ as an indicator. The titration reaction is: $$\ce{Ag+ + Cl- <=> AgCl}\tag{R1}$$ $$K_1 = \frac{1}{K_\mathrm{sp}(\ce{AgCl})} =...
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Determination of the iodine value of a fatty oil: Does the concentration of Na2SO3 effect the iodine value?

I want to determine the iodine value of a fatty oil. For this I dissolve $\ce{1.0 g}$ of the oil in chloroform. Iodine bromide is then added and placed in a dark room for at least $\pu{30 min}$. After ...
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Is it feasible to measure the pH of solution consisting of hydrofluoric acid, methanol and water using redox potential method?

Is it feasible to measure the pH of $\ce{HF}:\ce{H3COH}:\ce{H2O}$ solution using redox potential method? Can I use this method to calculate the $\ce{H+}$ ions in this solution and specifically, can I ...
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Inductively Coupled Plasma and Mass Spectrometry

I was doing some homework and I was reading about how ICP is suitable for mass spectrometry and it said how its high temperature favours ionization which is good in MS. But also, because the ...
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2answers
74 views

XRF is “non-destructive,” but what actually happens to the sample?

Editing for clarity and more details. My colleague has been using XRF to quantitatively analyze 47-mm diameter Teflon membrane filters for metals, minerals, and rare earths. Much of their analysis ...
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1answer
68 views

Difference between the terms “analyte” and “analyate” and their applicability

“Analyte” is the term that is usually universally understood and is listed in IUPAC Gold Book: analyte The component of a system to be analysed. However, recently I stumbled upon the word “...
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2answers
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What is the purpose of atomisation in atomic absorption spectroscopy? [closed]

What is the purpose of the atomisation process in atomic absorption spectroscopy? I understand that solution is evaporated by the flame and then the molecules decompose into atoms. But why must the ...
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142 views

Calculate the percent composition of a sodium carbonate/sodium bicarbonate mixture

In a lab, we titrated a solid mixture of sodium carbonate and sodium bicarbonate with $\pu{0.1 M}\ \ce{ HCl}$. We are asked to calculate the percent composition by mass of sodium carbonate and sodium ...
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Do the procedure used to find the empirical formula from combustion analysis be extended in other cases when is not specifically mentioned?

The situation is as follows: A sample of $\pu{19.40 g}$ from a certain compound consisting only in $\ce{K, Cr}$ and $\ce{O}$, receives a treatment. This gives $\pu{7.6 g}$ of $\ce{Cr2O3}$ and $\pu{...
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1answer
44 views

How does a mass spectrometer treat ions? [closed]

I always thought that in a mass spectrometer all the ionized fragments were going in the quadrupole at the same time, and then this quadrupole was sorting them by ratio. But last week I learn that a ...
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1answer
17 views

How do I scale up to semi-prep from an analytical HPLC [closed]

I am looking for an equation that would allow me to change the variables injection volume, column size, and flow rate scaling up from an analytical HPLC to a semi prep instrument.
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How to clean pocket pH meter before storage?

Hello. I read about different methods how to clean this specific(attached photo)pocket pH meter before storage and i can't figure out what is the right way. One method says to stir the pH meter(...
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1answer
87 views

How is antioxidant activity of carotenoids determined?

I am doing some research regarding carotenoids and beta-carotene. After extracting the sample, I have not been able to find a way to measure antioxidant activity of beta-carotene. I have $\pu{0.1mM}$ ...
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1answer
92 views

How can one determine an atomic mass with high accuracy using gravimetric analysis?

In the Wikipedia article on gravimetric analysis it is said that gravimetric analysis was used to determine the atomic masses of many elements in the periodic table to six figure accuracy. There are, ...
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56 views

Determining structure from C-NMR spectrum, is my answer correct?

Determine the structure of the compound whose spectral data is given below and explain your reasoning (5 marks for structure, 15 marks for reasoning). The peak at 7.27 ppm does not belong to the ...
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71 views

Which chemical is used in drunken driver test?

Which chemical is used in drunken driver test? Acidified K2Cr2O7 KMnO4 Chromyl Chloride H2O2 On searching on Google, I got the answer as option 1, acidified potassium ...
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Crystal structures of heaviest nuclides' compounds

What is the heaviest element of the periodic table for which there is a compound whose crystal structure has been completely resolved by X-ray diffraction?
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Home test for the presence of sugar in erythritol

Is there a test to distinguish erythritol from sugar at home without expensive lab equipment or exotic reagents? Sometimes I purchase erythritol online and wonder if it's been diluted with sugar.
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What does it mean to have coupling in H-NMR spectra? [duplicate]

That's the thing I didn't really get about NMR. By coupling, are the hydrogens coupled in that they split each other?
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64 views

When disolving a iron pill for titration, why do I use sulfuric acid instead of nitric or hydrochloric acid?

In a titration to decide the iron content of a pill we dissolved the iron in sulfuric acid and then titrated it with cerium(IV) sulfate. But I just wondered what's wrong with using nitric and ...
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2answers
103 views

Why does not aqua regia burn filter paper?

We were doing basic radical analysis in lab and we were asked to add aqua regia on the filtered PPT collected on the filter paper and collect the formed solution , my question is if aqua regia can ...