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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How do I solve this protolysis-reaction question? [closed]
I have measured $\mathrm{pH}$-values to these solutions and filled in a table:
$\ce{NaCl}:9.5-10$, $\ce{CH3COONa}:8$, $\ce{Na2CO3}:11.5$, $\ce{NaHCO3}:2$, $\ce{KNO3}:3$, $\ce{NH4Cl}:7-8$
The question ...
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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
$$
\begin{align}
\ce{...
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Does anybody have any ideas about the trend that I found for luminol chemiluminescence reaction? Or can anybody help me analyze them?
The reaction that I did is shown below. I'm testing the duration and luminosity of the light the reaction produces against different pH. The way I used to control the pH is by adding more or less $\ce{...
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1answer
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pH probe reading greater than 14
Today I was using my pH meter on wastewater samples but the meter was reading values near 14 and sometimes greater, I changed the probe with the spare one and it read well (sure I calibrated before ...
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597 views
How was pH measured back in the day if you had nothing to calibrate to?
We learn about indicators but these seem awfully useless if you have no clue what pH the color change occurs at. How did early chemists figure this out? I guess more broadly, how was the hydronium ...
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Ionic product value and pH/pOH
when studying basic acid and base reactions I got some conceptual question. When calculating the pH or the pOH of water we use the following formula:
$$\mathrm {pH}+\mathrm{pOH}=14$$
This comes from ...
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55 views
NaCl electrolysis with copper electrodes
Considering the aqueous $\ce{NaCl}$ is already concentrated. If we were to use copper electrodes instead of inert graphite electrodes:
Would copper react with the evolved chlorine gas to give $\ce{...
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1answer
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Electrolysis of Nacl with aluminium Electrodes
I conducted an experiment to find out the difference in products/ the final solution whilst using different electrodes. On using copper I obtained a teal blue soluble salt I believe to be $\ce{CuCl2}$ ...
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1answer
54 views
Autoionization of water
Consider as solution of pure water at $\pu{25 ^\circ{}C}$ with a $K_{\mathrm{w}} = 10^{-14}$.
If we are to add an acid to the mix we would observe an increase in hydronium and an equal decrease in ...
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What reaction is used for calculating pH of the solution obtained after ethanol oxidation with potassium permanganate?
If $\pu{30.0 ml}$ of $\pu{0.20 M}$ ethanol solution reacts with $\pu{1.80 g}$ potassium permanganate, what will be the final $\mathrm{pH}$ of the solution? Assume a complete reaction and that only the ...
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33 views
Which of the following can be a source of error in Spectrophotometry? Mark the wrong answer
a) Differences in solvent
b) Acid base equilibrium (differences of pH)
c) Parasitic or stray radiation
d) Monochromatic radiation
I have some doubts about pH in spectrophotometry. I'm not sure if it ...
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51 views
Electrolysis of brine solution gives sodium hydroxide , chlorine and hydrogen gas bur catner kellener cell it forms amalgam [closed]
Sodium hydroxide is generally prepared
commercially by the electrolysis of sodium
chloride in Castner-Kellner cell. A brine
solution is electrolyzed using a mercury
cathode and a carbon anode. Sodium ...
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3answers
80 views
salt hydrolysis and pH calculations
I am a high school student and I am very confused in salt hydrolysis
My confusion is that: when we talk of hydrolysis of salt of weak base and weak acid, we internally assume the degree of hydrolysis ...
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1answer
46 views
pKw, pKb, pKa and NEN6411
I am trying to understand how to account for pH-temperature relations during industrial pH measurements.
Do I have it right?:
The impact temperature has on the pKa of strong acids are in practical ...
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1answer
42 views
Why does the pH of a weak acid not increase by 1 when diluted by a factor of 10? [closed]
Strong acid pH increases by one unit when diluted by a factor of 10, but why do weak acids not?
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3answers
114 views
Temperature effects on pKa and pKw
I am an industrial electrician apprentice who needs to learn more about pH-measurements and how the temperature effects the measurement itself (I am in charge of all the pH measurements on the ...
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1answer
72 views
MgO as food supplement - solubility in water
A number of magnesium food / sports supplements contain it as MgO - which is practically unsoluble in water. The recommended quantity is somewhere around .3g / day, so not an insignificant amount.
How ...
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What are the compounds in oxygen and carbon dioxide indicator solutions that gives their color?
My brother had some leftover oxygen and carbon dioxide indicator solution for one of his take-home experiments from school, so he let me have them. I want to use them for an experiment and write out ...
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Why is aluminium oxide solution amphoteric? [duplicate]
Is Aluminium oxide solution amphoteric due to aluminium's electronegativity being in between 1.5 and 2.1.
If so why?
I believe it is because a AL-O-H molecule is made and it can either disassociate ...
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A trick to find resultant pH [duplicate]
Consider the following problem:
Find the $\mathrm{pH}$ of the solution formed by the mixing of two solutions of $\mathrm{pH}$(s) $2$ and $3$ of equal volumes.
The normal way:
Since the resulting ...
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How to measure chlorine content using ORP sensor?
In my project I need to measure pH, turbidity, and chlorine level of treated drinking water. I found sensors for measuring pH, turbidity, and also chlorine.
The actual problem begins is that the cost ...
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2answers
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In the pH system of acids and bases, are there 10^-7 loose ions per liter (at pH of 7) or per mole of solvent? (Or per mole of total substance?)
Most places tell me that the number on the pH scale tells you the number of dissociated ions, in moles, per liter of substance. But, Wikipedia's article pH says this....:
... For a commonplace ...
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pH Dependency of IR Stretching Frequency in CO-binded Heme Protein
If one consumes CO, then CO binds with Heme Protein forming a Fe-CO bond. My question is if there will be any pH dependency on IR Stretching Frequency, i.e. ν(CO) and ν(Fe-CO). And if there is, then ...
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How can water below a pH of 7 still be alkaline?
Alkalinity is a measure of the water's ability to neutralize acidity and is expressed in levels of bicarbonates, carbonates, and hydroxides.
How can water that is slightly acidic, e.g. 5.5-6.5, still ...
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pKa = pH for strong acid — strong base?
I have learnt that for a weak acid — strong base titration, $\mathrm{p}K_\mathrm{a} = \mathrm{pH}$ at the half equivalence point.
However, the same conclusion is not drawn when discussing strong acid —...
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2answers
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Why is the gradient of the curve of a strong base titrated with strong acid small up until equivalence?
I understand the cause of the sharp decrease in pH upon reaching the equivalence point, but I don't understand why addition of relatively large amounts of the strong acid would be accompanied with ...
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2answers
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Effect of dilution on weak acids pH [closed]
My textbook has a question which says what would happen to the pH of a weak acid if it is diluted with water. The answer is its pH would decrease.
My teacher’s argument is that it would indeed ...
3
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1answer
141 views
What is the difference between these two formulas for pH of weak acids?
In the German Wikipedia article on $\mathrm{pH}$, I found the following formula for calculating the $\mathrm{pH}$ of weak acids (which are there defined of having $4.5 < \mathrm{p}K_\mathrm{a} < ...
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How does flocculation in paint work?
I recently learned that you can clean up latex paint wash-up water by flocculating it: adding aluminum sulfate and hydrated lime. I vaguely remember how flocculation works in clay slurries (change in ...
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1answer
80 views
How to set up an ICE table for adding a weak acid to a strong acid
I am working on setting up an ICE table for adding 0.020 mol HCl to 1.0 L of 0.10 M propanoic acid. Since these are both acids (propanoic acid being the weaker one and HCl being strong), how would I ...
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What colour ranges would a solution of Methyl Orange and Thymol Blue have
Would the solution of Thymol blue and Methyl orange tell the difference between an acid with ph 2.1 and anther acid with ph 2.2?
I am a chemistry beginner, so I don't understand the reactions on that ...
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1answer
38 views
pH scale at various temperatures
I am an electrician apprentice in charge of a large number of pH-sensors/transmitters at a power plant and chemical plant.
I do all the pH-instrumentation related maintenance, calibration, adjustments ...
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Why is aqueous solution of lauyl glucoside alkaline?
What is the reaction of dissociation of lauryl glucoside? It's aqueous solution pH is much higher than 7, it's definately alkaline. Why is that? It's nonionic surfactant and as far as I know it only ...
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Is lauryl glucoside stable in low pH?
I wish to use lauryl glucoside in the solution of citric acid. I tried to add it to 5% w/w solution of citric acid in water but after about 24h in the concoction which was previously clear I observed ...
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1answer
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Weak acids compared to strong ones in pH > 7 solution
In the book of Molecular Cell Biology (Big Alberts) by Alberts, at page 46, it is stated that
Acids—especially weak acids—will give up their protons more readily if the concentration of > H3O+ in ...
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1answer
53 views
Is it possible to make a solution of zinc oxide in a high school chemistry lab?
As part of my IB Chemistry curriculum, we are required to conduct our own experiment researching our own question. I'm in the preliminary research phase and wanted to conduct an experiment looking at ...
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2answers
251 views
How to make acetic acid more volatile so that it can be removed by vigorous aeration of an acetic acid-water mixture? [closed]
I want to remove acetic acid from a mixture of acetic acid and water by aeration. The concentration of acetic acid is 200 ppm (mg/L). The pH of the water is more than 5. I want to reduce the acetic ...
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1answer
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Modelling pH as function of time and position
I already posted this on the Engineering Stack Exchange under Chemical Engineering as I don't know where it's a better fit.
I have a system whose initial state consists of three different sections ...
4
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1answer
492 views
Why are there no alkaline foods?
It takes some work to find a list of the actual pH of various foods. (Searches are confounded by a popular "alkaline diet" theory that the pH effect on a human body of consuming various ...
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2answers
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Is an aqueous solution of potassium bicarbonate acidic or basic in nature?
The following is the definition of an acid salt according to my textbook:
The salts formed by the partial replacement of the replaceable hydrogen atoms (H+ ions) of an acid molecule by a metallic or ...
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1answer
134 views
How to change pH of CuSO4?
I'm currently very desperate to know this. I'm doing an experiment about adsorption/chelation of Cu ions in CuSO4 using banana peels using the UV-Visible spectroscopy. How do I change the pH of 0.1M ...
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What has happened with the pH-meter?
The glass sensor has became red inside like something melted. I stored it in a liquid with pH that mentioned in the manual. What is that and why could that happen, how often that happens with pH-...
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2answers
154 views
Why is sodium bicarbonate added to lower the pH? [closed]
I use salicylaldehyde, chloroacetic acid and sodium hydroxide for the synthesis of o-formylphenoxyacetic acid. In the procedure it is written that after the reaction I need to add sodium bicarbonate ...
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How does a change in pH affect the colour of a leuco dye in a thermal paper?
I am investigating the way that a leuco dye is released in thermal paper once heated. I have understood that leuco dyes, when in their colourless state are encapsulated in an acid developer in the ...
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1answer
335 views
Why are amino acids least soluble at isoelectric point?
At isoelectric point amino acids exist as zwitterions. As a molecule it is electrically neutral, but still has a positive and a negative charge. Then why are amino acids still least soluble at ...
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1answer
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Find volume of ammonia gas required to prepare a solution of given pH [closed]
Calculate the volume of gaseous ammonia $(K_\mathrm{b} = \pu{1.8E-5})$ to dissolve (at NTP) in $\pu{100 mL}$ of water in order to obtain a solution with $\mathrm{pH} = 11.0.$ Consider volume variation ...
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1answer
191 views
Common Ion Effect - Ionic Equilibrium
Question
In which of the aqueous solutions of the following, dissociation of $\ce{NH4OH}$ will be minimum?
A) $\ce{NaOH}$
B) $\ce{H2O}$
C) $\ce{NH4Cl}$
D) $\ce{NaCl}$
My Thoughts
My book says that ...
0
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1answer
178 views
Which one of the two is the stronger base: methoxide ion or hydroxide ion? [duplicate]
If we consider the experimentally determined pka values, it looks like hydroxide ion should be the right answer but in many books it has been mentioned that all alcohols are less acidic than water ...
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0answers
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6463-T6 aluminum oxidation and role of water and ethanol vapor
Our issue...in a nutshell: We use 6463-T6 aluminum as a sampling "cell" for analysis of water and ethanol vapor mixtures in both wet and dry gas variations. As I understand it, the ...
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How to calculate the pH of solutions of amphoteric salts? [duplicate]
I've been trying to understand how to calculate the pH of solutions of amphoteric salts, but I just can't figure it out. So, I've seen that it is commonly explained like this (example for a solution ...
