Questions tagged [ph]
pH (or the potential of hydrogen) is a scale used to measure how acidic or basic an aqueous solution is.
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pKa calculation problem
a known amount of pure acid is dissolved in a known amount of amphoteric solvent. Given that the volume of the titrant base needed from the starting point of color change to the end point is known, ...
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How will the dielectric constant of water change when ethyl acetate is added?
How will the dielectric constant of water change when ethyl acetate is added?
The $\mathrm{p}K_a$ value of weak acids in aprotic solvents will be lower than in protic solvents because the dielectric ...
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How to achieve desired pH using two buffer Solutions with two different pHs? [closed]
To purify a certain protein, you were required to prepare a $\pu{0.10 M}$ glycine buffer at $\mathrm{pH} \: 9.4$. Unfortunately, the stockroom has run out of glycine. However, the lab aides were able ...
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1answer
46 views
Accurate method to calculate the pH of a salt from a weak acid and weak base
Can someone help me with this?
The problem is as follows:
Find the $\mathrm{pH}$ of $\pu{1M}$ solution of $\ce{NH4CN}$. Their respective
hydrolysis constants are:
$K_h = 5.6\times 10^{-10}$
...
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0answers
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Calculating pH and pOH of acidic solutions [closed]
Calculate the the $\mathrm{pH}$ when $\pu{1M}$ of $\ce{HCl}$ acid dissociate in water?
In this question most of books solve it by taking the concentration of $\ce{H+}$ as $\pu{1M}$ and the $\mathrm{...
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How to find the molar concentration of two compounds mixed together in a buffer solution having the Kb and its Ph [duplicate]
Calculate how many milliliters of a $\pu{8.00 \times 10^{−1} M}$ solution of $\ce{NH3}$ and how many milliliters of a $\pu{7.80 \times 10^{−1} M}$ solution of $\ce{NH4Cl}$ are needed to get to a liter ...
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pH responsive polymer which is immiscible in water?
Can anyone suggest a pH-responsive polymer, which is immiscible in water (polar solvent) but miscible in oil (e.g vegetable oil)?
I want to study the change in the density of such polymers when they ...
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1answer
18 views
How does increasing the Hydrogen Concentration of CuSO4 (electrolyte) affect electroplating of copper
I'm trying to find an answer as to how lowering the pH of the CuSO4 solution during electroplating of copper affects the amount of copper deposited onto the cathode.
My very basic understanding is ...
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1answer
44 views
Finding Ka of a monoprotic weak acid from pH and concentration of added sodium salt
A solution of $\pu{0.36 M}$ of the sodium salt of a generic monoprotic weak acid $\ce{HA}$ has a $\mathrm{pH}$ value of $8.782.$ $K_\mathrm{a} = ?$
Why doesn't the following formula work in this ...
1
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1answer
46 views
Can ascorbic acid be neutralized and keep it's elastic properties in dough?
Ascorbic acid (C6H8O6) is commonly used in dough to give it strength and elasticity. However, I need this dough to be alkaline, or at the very least neutral. I've used sodium carbonate (Na2CO3) before ...
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pH of amphoteric species
For a solution of $\ce{HA-}$, I have seen the following approximations for the $\mathrm{pH}:$
$$\mathrm{pH} = \frac{1}{2}(\mathrm{p}K_\mathrm{a1} + \mathrm{p}K_\mathrm{a2})\tag{1}$$
$$\mathrm{pH} = \...
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3answers
75 views
Tap water pH adjustment using citric acid
I've lowered tap water pH from 7 to 6 using citric acid. After couple of hours pH raised again to 7.
What is the reason for this raise? Citric acid overcomes waters buffering feature then raise the $...
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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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2answers
71 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 ...
3
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0answers
16 views
Acidity comparison on R-PO3H2
Question
Compare the acidity $(K_\mathrm{a1})$ of the following three acids:
$\ce{H3PO4},$ $\ce{Ph-PO(OH)2}$ and $\ce{H3C-PO(OH)2}.$
Thoughts
These three acids are of type $\ce{R-PO3H2},$ where ...
3
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2answers
158 views
Use of Concentration for pH
When we find the pH of a solution, do we use normality or molarity? My teacher said that if the compound is present by itself, we can use normality but in all other cases we should use molarity. Can ...
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3answers
122 views
Fitting multiple pKa's
I have three histidine residues that are next to each other in a protein. When I compute the fraction of unprotonated states for each individual histidine as a function of $\mathrm{pH}$ my titration ...
0
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1answer
85 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 $\...
3
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1answer
56 views
Is there a relationship between acidity of the water solution and oxidation/reduction reactions?
What I want to know is if there is a relationship between the acidity of the water solution and redox reactions and if there is a relationship what favors the oxidation and what favors the reduction? ...
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Is contribution to pH by an acid or base always greater than salt hydrolysis?
I was solving a titration question and the reaction I came to was this:
$$
\begin{array}{lcccc}
\ce{&BOH(aq) &+ &HCl(aq) -> &BC(aq) &+ &H2O(l) }\\
\text{Initial} & x &...
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0answers
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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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2answers
44 views
Can I make a buffer with a weak acid without adding it's conjugated base, when the desired pH of the solution is exactly the pKa of the weak acid?
An acid will be 50% dissociated when the solution it's in have a pH equal to the acid pKa ('afirmation 1', for later reference).
We also know that a good buffer solution have equal concentrations of ...
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1answer
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pKa of phenols using UV-Vis spectroscopy
I have done an experiment where I dissolved four different substituted phenols in acidic, basic, and buffer solutions, and recorded the UV-Vis spectra for each. I'm supposed to pick a wavelength where ...
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0answers
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What is the pH and pKa relationship of LaCl3 in water and its precipitant La(OH)3?
In light of this question and its answers, I hope to get some insights into the $\mathrm{pH}$ of $\ce{LaCl3}$ in water and its $\mathrm{pH}$ relationship to $\ce{La(OH)3}$ precipitant's $\mathrm{p}K_\...
2
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1answer
75 views
How to calculate the number of protons in a sphere given the volume and the pH?
The spherical radius of a nano-droplet of a solution ($\mathrm{pH}$ of which is $6$) is given as $\pu{20nm}$.
I can find the molar concentration of $\ce{H+}$ and subsequently the number of $\ce{H+}$ ...
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0answers
51 views
Hydronium ion concentration to compare pH values
I'm having a bit of trouble with this question:
Which has a higher $\mathrm{pH}$ value, $\pu{0.001 M}$ $\ce{HCl}$ or $\pu{0.1 M}$ $\ce{CH3COOH}$ $(K_\mathrm{a} = \pu{1.8E-5})?$
I have calculated ...
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How to calculate Revelle factor using only pH, DIC and TAlk for seawater?
I have the temperature, salinity, $\mathrm{pH},$ dissolved inorganic carbon (DIC) and total alkalinity (TAlk) values for an estuarine water sample. I want to calculate the Revelle factor.
The Revelle ...
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Calculating pH of a saturated weak acid/base solution [closed]
How can you calculate the $\mathrm{pH}$ if you know for example the $\mathrm{p}K_\mathrm{a}$ or $\mathrm{p}K_\mathrm{b}$ value of a weak acid/base and how much acid/base can dilute in water. Let's ...
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173 views
Is black tea a pH indicator?
Today, I made a cup of lemon tea in a different way than usual. Instead of pouring hot water in to a mug containing lemon juice and black tea (my normal routine), I let the tea steep for a little ...
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2answers
70 views
Finding pH of acid in water [closed]
How would you find the pH of an acid dissolved in water? Would you need to take the fact that the pH of water is already 7 into account and go on from there?
Say, for example, that you add 0.0500 mL ...
1
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1answer
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Why CO2 is not reducing the pH of NaOH as the way it is expected
I am using $\ce{CO2}$ for the reduction of pH of $\ce{NaOH}$ solution ($\pu{2.5g}\; \ce{NaOH} + \pu{250ml}\; \ce{H2O}$, with $\mathrm{pH}\; 13+$).
I am introducing $\ce{CO2}$ with different dosages ($\...
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1answer
187 views
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 $\pu{0.20 M}$ $\...
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Is pH in a charged hydrogel and its supernatant solution constant?
Let us assume we deal with ideal systems without interactions.
The gel phase and the supernatant solution phase are in thermodynamic equilibrium. The supernatant solution shall consist of different ...
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93 views
Can a universal indicator turn colorless?
I learned that litmus paper could be bleached by chlorine to turn colorless. I’m wondering if any chemical substances can react with all the components of a universal indicator such that it turns ...
2
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1answer
112 views
Ratio of uncharged to charged side chains [closed]
The $\mathrm{p}K_\mathrm{a}$ of the side chain imidazole group of histidine is $6.0.$ What is the ratio of uncharged to charged side chains at $\mathrm{pH}~7?$
Here's my attempt to the solution:
$$7 ...
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0answers
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How do I find pH of a mixture of weak acids? [duplicate]
Suppose that we are given two weak bases $\ce{HA_1}$ and $\ce{HA_2}$. We are also given the $K_\ce{HA_1}$ and $K_\ce{HA_2}$. How can we calculate the $\mathrm{pH}$ of the mixture?
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1answer
434 views
How do I calculate the ensemble-average net charge of an amino acid at given pH?
I am given an amino acid with an ionizable side chain at a certain pH. How do I determine the net charge of that amino acid when there are mixed protonation states of one or more of the groups at that ...
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0answers
130 views
Calculating ionic strength and pH of a buffer solution [closed]
Im trying to calculate ion strength and pH of solution.
Components of the solution:
47 ul of 1000 pmol DNA in Elution Buffer (10 mM Tris-HCl pH 8.5) was bound to 3 ul of 10 µM YoYo1 (flourescent dye) ...
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1answer
40 views
How can I prepare two phosphate buffer of different concentrations but give same pH? [closed]
How is it that buffers of different compositions can have the same pH? For example, it is possible to prepare 0.01 M phosphate buffer of pH 7.0 and 0.1 M phosphate buffer of pH 7.0? How?
I used ...
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1answer
84 views
Why can Neutral Red (indicator) not test values below its pKa?
It is the only indicator I have found that does not test below its pka, and can't think of any reason for this.
Neutral Red has a pKa value of 6.8.
(
Reference 1,
Reference 2
),
but looking at its pH ...
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1answer
53 views
How a titration curve is affected when a poorly soluble salt is formed?
Suppose that I have $\pu{100 mL}$ solution of strong acid, $\ce{HA}$, at $\pu{0.10 mol L^{-1}}$.
This solution is titrated with a strong base solution, $\ce{BOH}$, at $\pu{0.10 mol L^{-1}}$.
Suppose ...
2
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0answers
23 views
How to control pH in a fermenter based on the acid produced by mircoorganism
I have got a bioreactor with an aqueous medium which produces biomass (yeast; S.cerevisiae) after inoculation.
I am observing and collecting data over the whole process via probes/etc. on different ...
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2answers
61 views
Finding the pH of the solution
In this video, at 3:30 min professor solves two equations
$$\ce{H2O —> H+ + OH-}$$
and
$$ \ce{HCl —> H+ + Cl-}$$
and deduces $[\ce{H+}] = [\ce{Cl-}] +[\ce{OH-}]$. How come this happen from ...
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0answers
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pKa values for amino acid
To calculate the pI value, we take the average of the pKa values from the 2 groups that result in a net charge of 0.
For that to happen, the pKa values should be at the midpoint of titration where ...
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1answer
47 views
How to predict whether a salt will act as an acid or as a base in aqueous medium? [closed]
How to would we know if a salt such as $\ce{CO_2}$ reacts acidic or basic in water.
The explanation I see everywhere is that you have to see the acid and base that makes up the salt, in the case of $\...
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1answer
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The time-dependent pH value in a fermentation
I want to know if someone has supporting tips or solutions to my problem:
In biotechnology, fermentations are used to grow microorganisms. These need a specific media/broth in which temperature, pH, ...
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1answer
135 views
How does sodium carbonate reduce pH?
Sodium carbonate is used in pools to raise pH. From my understanding, it would dissociate in water like so:
$$\ce{Na2CO3 <=> 2 Na+ + CO3^2-}$$
To raise pH, doesn't it have to absorb hydrogen ...
3
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0answers
43 views
Effects of gamma irradiation on pH buffer
Does anybody know if it is possible to gamma-irradiate a bottle of pH buffer to sterilise it? Are there any known effects (short-term or long-term) of the irradition process on the pH qualities of the ...
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70 views
What is the pH of a solution of iron acetate?
What is the pH of a $\ce{0.1 M}$ solution of $\ce{Fe(CH_3COO)_3}$? I'm not sure how to do this, as it would involve complicated mass balance equations, but I think I can apply the approximation $\ce{...
1
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1answer
47 views
Acid solution — lower pH when diluted
Today I came across a "thought experiment" regarding $\mathrm{pH}$ of a diluted acid solution. This idea looks somewhat logical but obviously contradicts the reality. Can you show me where is the ...
