All Questions
Tagged with aqueous-solution analytical-chemistry
50
questions
22
votes
2
answers
5k
views
pH probe bulb - what is happening within the glass?
I am trying to understand how the glass bulb of a pH electrode of a pH meter works - the glass bulb itself. Not the reference electrode or the rest of the electrode (HCl, Ag/AgCl wire, etc...), the ...
- 5,900
9
votes
2
answers
1k
views
Why does Devarda's alloy include copper?
Devarda's alloy is used in the detection of nitrates. However, judging by the reaction equation, only aluminium plays the role of reducer:
$$\ce{3NaNO3 + 8Al + 5NaOH + 18H2O -> 8Na[Al(OH)4] + 3NH3(...
- 3,276
7
votes
1
answer
11k
views
Why does phosphoric acid mask the colour of iron(III) complex in water?
In the redox titration of iron(III) with permanganate or dichromate, we use phosphoric(V) acid to "mask" the color of iron(III) because it interferes with the end point color change.
What's the ...
- 115
6
votes
1
answer
7k
views
Difference in calculated pH and the real pH of a phosphate buffer
I want to prepare a buffer system with $\mathrm{pH} = 7.00$ and a total concentration $c_\mathrm{tot} = \pu{0.10 mol l^-1}$ using sodium hydrogen phosphate $(\ce{Na2HPO4})$ and sodium dihydrogen ...
- 71
6
votes
1
answer
120
views
How much additional hydrochloric acid should be added to arrive at ‘excess acid’?
I am an IB student. And I am trying to find the mass percentage of $\ce{NaHCO3}$ in antacid. I am dissolving the antacid in $\pu{0.1 M}$ $\ce{HCl}$ solution. So, first of all I conducted some ...
- 263
5
votes
1
answer
2k
views
Calcium ion and sulfate did not form precipitate
I was in the chemistry lab earlier this week. We were doing a qualitative experiment (no concentration given for any solution).
I added an unknown solution that contains $\ce{Ba^2+},$ $\ce{Ca^2+},$ ...
- 205
5
votes
1
answer
440
views
Is chromate a suitable indicator for the titration of Ag⁺ with Cl⁻?
To titrate $\ce{Cl-}$ with $\ce{Ag+}$ we use chromate $\ce{CrO4^2-}$ as an indicator.
The titration reaction is:
$$\ce{Ag+ + Cl- <=> AgCl}\tag{R1}$$
$$K_1 = \frac{1}{K_\mathrm{sp}(\ce{AgCl})} =...
- 187
5
votes
0
answers
159
views
Where is my antimony going?
I work in a trace metals laboratory operating an ICP-OES. I've been having some trouble with the recovery of antimony in a weak $\ce{HCl}$ solution post-digestion.
The antimony is part of a mix of ...
- 51
4
votes
3
answers
2k
views
Are refractive or density based Brix meters better for use with alcoholic drinks?
Assume that somebody wants to measure the sugar content of a liqueur. It seems that there are two types of Brix meters for it, ones which use the solution density and ones which use refraction of ...
- 478
4
votes
4
answers
247
views
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
4
votes
3
answers
947
views
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
4
votes
1
answer
164
views
Best x-ray dopant?
An x-ray computed tomography scanner has been used in an attempt to look at the pore space of a limestone rock sample (a carbonate, $\ce{CaCO3}$) saturated with a $\mathrm{12\ wt\%}$ sodium iodide ($\...
- 187
3
votes
2
answers
1k
views
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
votes
3
answers
3k
views
What is the procedure to create stock solutions?
Until now to execute this recipe, each time i had to count those milligrams/Liter. An enough difficult procedure.
I am posting here this question to help me understand the procedure of creating ...
- 159
3
votes
1
answer
598
views
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 ...
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