All Questions
Tagged with aqueous-solution analytical-chemistry
50
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How to dissolve a powdered drug once it has been mixed with water
For a biological experiment I have acquired $\pu{10 mg}$ of CHIR 99021 (laduviglusib). In order to obtain a $\pu{10 mM}$ stock solution, I had to dissolve the powder in $\pu{2.15 mL}$ of dimethyl ...
- 19
2
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0
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75
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Stability of n-Dodecyl-beta-D-maltoside in buffer solutions for assay experiments
I have a buffer system which contains multiple salts and in addition DTT and n-Dodecyl-beta-D-maltoside.
I understand that DTT is hydrolysing quite fast and this component must be used always fresh ...
- 799
1
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0
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76
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What does it mean for a substance to be "sparingly soluble"?
I have trouble understanding what solubility means. Merriam-Webster defines it as follows:
1 the quality or state of being soluble
2 the amount of a substance that will dissolve in a given amount of ...
- 67
2
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1
answer
86
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Are all salts completely dissociated in solution when put in smaller amounts than their molar solubility?
From what I understand, the solubility is given in terms of molar solubility (or $\pu{K_{sp}}$), from which it can be easily calculated). Indeed, the saturation point represents the maximum amount of ...
- 67
1
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2
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182
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What is the inconsistency in calculating the differences in Na2O and NaOH in solids (v2)?
(Note that this question has been fully edited for clarity, SE help advised not to delete the question and post another).
Background:
I have a computer model in which I feed it input data from various ...
- 500
4
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4
answers
247
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Determining the concentration of a very small sample of sulfuric acid
How can we determine the concentration of sulfuric acid in a very small sample?
We are working on a “mechanical” process that transports a very small amount of sulfuric acid to an instrument and we ...
- 41
3
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2
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1k
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Magnesium vs calcium vs barium ions from these 3 tests
How do I pick up the difference between barium, calcium, and magnesium ions? I had to do a quantitative analysis practical exam: I was given an aqueous solution of a salt, and when adding separately ...
-3
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1
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Determining iron(III) content in mixture of iron(II) and iron(III) [closed]
Problem
Outline a plan of an experiment to determine the percentage of iron present as iron(III) in a solution containing $\ce{Fe^3+(aq)}$ and $\ce{Fe^2+(aq)}$ ions. You are provided with zinc, a ...
- 15
1
vote
1
answer
70
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An Index Poisoning Case Involving Dichlor and Carbonic Acid [closed]
I'm currently working an unusual case of poisoning, with Sodium Dichloro-S-Triazinetrione.
In my case, I need to know the expected reaction with carbonic acid.
I'm also curious if anyone could give ...
- 11
3
votes
1
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598
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pH meter mechanism - connecting potential differences
This question was asked here: pH probe bulb - what is happening within the glass? and How does a pH glass electrode work?.
But, the mechanism remains unanswered. How does a potential difference ...
- 39
0
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1
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38
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Disparity between LeChatelier's Principle and Solutions
Let's say that there is a solution
$\ce{Na+(aq) + Cl-(aq) <=> NaCl(s)}$
If the above solution is at equilibrium we can say that it is saturated and hence no more Sodium Chloride will dissolve. ...
- 151
0
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138
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Problem in the calculation of ionic strength of a solution
Recently I've been trying to answer the question 10-13 (c) of 9th edition of Fundamentals of Analytical Chemistry of Skoog et al. Comparing my answers with the student manual , I realized that my ...
- 177
1
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0
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85
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Alkalinity measured by titration after degassing of CO2
I recently received some lab results from a sample which contained a lot of CO2, which degassed before the total alkalinity was measured by titration to a pH 4.5 end point. The best analogue for this ...
- 31
0
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1
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1k
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Determining the mass of a substance using calibration curve produced by HPLC
I hope everyone is doing well and safe! Yesterday, I was fortunate enough to be taught about how to read a chromatography calibration curve through this stackexchange! Special thanks to those who ...
- 87
1
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117
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Can analytical precision be finer than a lower detection limit?
Can analytical precision be finer than a lower detection limit?
For example, if the lower detection limit of an analytical method is reported as 0.010 ppm. Is it possible to have an analytical ...
2
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0
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Is there a reason why we add (CH3CSNH2) but not H2S in qualitative group analysis? [closed]
Brief question: In $\ce{Cu}$-$\ce{As}$ group analysis we are expected to add thinoacetamide to make a precipitate with sulfide. Can we use $\ce{H2S}$ instead?
- 103
2
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1
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974
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Creating a 10 ppb Lead Nitrate Solution
I’m trying to make a 10 ppb Lead Nitrate solution as part of a concentration calibration step for a Beer Lambert’s Law experiment. I plan on performing a dilution in three steps. The calculations have ...
- 467
1
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1
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372
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Creating 1L of 1000 ppb stock solution of Pb2+
I’m testing on samples that require a concentration of 1000 ppb (or 1 mg/L) of Pb 2+. My first thought was to simply dissolve 1 mg of Lead nitrate in 1 L of deionized distilled water to create 1 L of ...
- 467
2
votes
1
answer
105
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Can o-phenanthroline be used as a complexing agent for lead(II)?
I’ve been trying to find a method to perform a spectrophotometric analysis to determine lead concentration (on the ppm level). This would require some chelator capable of forming a coloured complex ...
- 467
4
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3
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947
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Chemicals that form coloured complexes with Pb(II) cations
I’m currently conducting a photo-spectrometric analysis of lead concentration in water, and was looking into using Eriochrome Black T (EBT) as an indicator for $\ce{Pb^2+}$ (due to the complex forming ...
- 467
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3
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231
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Is it possible to measure light absorbance for analysis of lead concentration without photospectrophotmeter
I’m designing an experiment which requires I measure final and initial lead concentrations for the determination of aqueous lead uptake by different mediums. Because lead concentrations would be ...
- 467
2
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1
answer
123
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How concentrated does the analyte solution need to be in order to perform a (chelatometric) titration
I’m currently investigating a method to chemically pretreat cellulosic waste as bisorbents for enhanced uptake of lead in water. I intend to measure the initial and final concentration of water to ...
- 467
-1
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1
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43
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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 ...
- 249
5
votes
1
answer
440
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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})} =...
- 187
5
votes
1
answer
2k
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Calcium ion and sulfate did not form precipitate
I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).
I added an unknown solution that contains $\ce{Ba^2+},$ $\ce{Ca^2+},$ ...
- 205
1
vote
1
answer
2k
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Preparation of acetate buffer from sodium acetate and hydrochloric acid
A $\pu{1.0 L}$ buffer solution of $\mathrm{pH}~4.43$ is made up of $\pu{0.30 M}$ sodium ethanoate and $\pu{0.20 M}$ $\ce{HCl}$ solutions. Calculate the volume of sodium ethanoate and $\pu{0.20 M}$ $\...
2
votes
1
answer
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Why do we use hydrochloric in the test for sulfate ions but nitric acid for halide ions?
Recently, I have learnt about testing for ions in qualitative analysis (BBC Bitesize).
The link above which I used for reference mentions that for the test for sulfate anions, hydrochloric acid $(\ce{...
- 235
0
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1
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161
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Redox titration or iron(II)
The concentration of $\ce{Fe^2+(aq)}$ can be determined by a redox titration using
A. $\ce{KBr}$
B. $\ce{SnCl2}$
C. $\ce{KMnO4}$ (basic)
D. $\ce{KBrO3}$ (acidic)
Can anyone please help me on this ...
- 11
2
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1
answer
212
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Percent Dissociated from Titration Curve
Question 818 references the titration curve. Answer is A because $\ce{H+}$ conc $= 10^{-4}$. This is conc of dissociated acid. The conc of the undissociated acid is the original concentration minus ...
- 43
2
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1
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829
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Why is maximum buffer capacity for some diprotic buffers not when pH = pKa?
According to Rajkovic et al. [1]:
$$β = \frac{[\ce{H+}]}{K_\mathrm{w}} + 2.303\cdot\frac{[\ce{H+}]\cdot K_\mathrm{a}\cdot c}{[\ce{H+}] + K_\mathrm{a}}$$
where $K_\mathrm{a}$ is the dissociation ...
- 103