All Questions
24
questions
0
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21
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Dissolution of portlandite, calcite/CaCo3 phase and C-S-H due to high pH
I would like to ask about the possibility of the partial dissolution, over curing time, of portlandite, CaCo3 and C-S-H phases due to high pH (12.5 - 13) of the lime-clay-water systems (lime-...
- 1
3
votes
1
answer
805
views
When NaOH ionizes in water, does the OH– react with the water molecules or with the hydronium ions from the dissociation of water?
NaOH in water becomes $\ce{Na+}$ and $\ce{OH-}$ ions. If it's a Bronsted Lowry base then the $\ce{OH-}$ ions will take $\ce{H+}$. But FROM where exactly - from the water molecules or from the ...
-5
votes
1
answer
59
views
Why is 10 times phosphate-buffered saline more acidic (~6.9) than 1 time phosphate-buffered saline (~7.4)? [closed]
Recently, I've been told that similar pH shift (of about 0.5 units) was observed with 20 times NPS solution as well.
In case of NPS the authors provide the following recipe for the 20 times solution:
...
- 111
1
vote
3
answers
239
views
Discrepancies in using pOH vs pH to solve H+/OH- concentration change problem
I found an extremely confusing problem in one of the problems we did in class for general chemistry. This was the question:
How many moles of $\ce{H3O+}$ or $\ce{OH-}$ must you add per liter of $\ce{...
- 21
1
vote
0
answers
52
views
How to calculate pH resulting from dissolving a salt in water? [closed]
The main question is how to calculate the changes in pH after dissolving a salt in water.
Suppose we dissolve 1 gram of magnesium carbonate (MgCO3) in 1 liter of Water. This will result in (...
- 11
0
votes
2
answers
194
views
What might cause overestimated measured pH value of sodium hydroxide solution pumped with carbon dioxide?
I tried an experiment at home where I had a $\ce{CO2}$ tank pumping $\ce{CO2}$ into a solution of $\pu{28 g}$ sodium hydroxide in $\pu{200 ml}$ water. The initial $\mathrm{pH}$ was $11.24.$
I expected ...
- 59
-1
votes
1
answer
513
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How to calculate how much weak acid would dissociate in water?
So I know water has a pH of 7. If we add 0.1 mol of a strong acid inside 1 liter of water, it WILL fully dissociate into 0.1 mol of A- and 0.1 mol of H+ thus making the pH of the solution 1.
But what ...
0
votes
1
answer
786
views
Why is the solution of ammonium bifluoride more acidic than aqueous ammonium fluoride?
At low concentrations of aqueous $\ce{NH4HF2}$ $(w = 1–2\,\%)$ $\mathrm{pH}\approx 3.$
But aqueous $\ce{NH4F}$ $(w = 20–40\,\%)$ has $\mathrm{pH}\approx 7.$
Yet the equilibria of
$$
\begin{align}
\ce{...
- 421
2
votes
4
answers
2k
views
Help with determining concentration of magnesium hydroxide for a specific pH level
This seems like such an obvious and elementary-level question for someone who has taken high school chemistry, but yet I'm having a difficult time solving it. I need to find the right amount of $\ce{...
- 139
1
vote
1
answer
769
views
Calculating the biological standard potential
I have an electrochemical cell with following overall reaction:
$$\ce{5 Sn^4+ + 2 Mn^2+ + 8 H2O <=> 5 Sn^2+ + 2 MnO4- + 16 H+}$$
I have defined the half reactions as:
$$
\begin{align}
\ce{Sn^...
- 29
0
votes
2
answers
385
views
Acidic nature of boric acid when its concentration high
Following statement was given for boric acid $(\ce{H3BO3}):$
At low concentrations $(\leq\pu{0.02 M})$ essentially $\ce{B(OH)3}$ and $\ce{B(OH)4-}$ are present, but at higher concentration the ...
- 1,350
3
votes
2
answers
821
views
Calculating pH of rain water
The concentration of $\ce{SO2}$ in the atmosphere over a city on a certain day is $\pu{10 ppm}$. Given that solubility of $\ce{SO2}$ in water is $\pu{1.3653 mol L-1}$ and $\mathrm{p}K_\mathrm{a}$ of $\...
- 224
1
vote
1
answer
221
views
Titration of barium(II) hydroxide by hydrochloric acid
$\pu{25 ml}$ of $\pu{0.024 M}$ $\ce{HCl}$ is titrated into a volumetric flask which initially contains $\pu{45 ml}$ of $\pu{0.034 M}$ $\ce{Ba(OH)2}$. Calculate the $\mathrm{pH}$.
This is how I ...
- 19
0
votes
0
answers
63
views
Calculating pH of solution
What is the $\mathrm{pH}$ when you dissolve equal amounts of $\ce{NaHCO3}$ and $\ce{Na2CO3}$ in water?
When both of the compounds are dissolved, we will have equal amounts of $\ce{HCO3-}$ and $\ce{...
- 79
0
votes
0
answers
384
views
Preparation of Copper (II) Sulfate Pentahydrate Solution
how would you make a solution of Copper (II) Sulfate Pentahydrate to achieve 150, 200, 250 and 300 mgL−1 concentration of copper? I do not have the anhydrous version of the solute. Also, when I ...
