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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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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63 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
35 views
Bleach discoloration [closed]
Juice of aloe Vera left marks on a white laminate benchtop. I tried to remove it with bleach but for some reason the beach made it worse and left a large yellow trail. The bleach came in contact with ...
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Finding the best indicator for titration of a weak base and strong acid (NH3 + HCl) with only a Ka value
The best indicator to use in a standard titration of aqueous $\ce{NH3}$ $(K_\mathrm{a}(\ce{NH4+}) = \pu{5.7E-10})$ with an $\ce{HCl}$ is
$$
\begin{array}{llc}
\hline
& \text{Indicator} & \...
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1answer
58 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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0answers
23 views
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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0answers
15 views
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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0answers
40 views
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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2answers
58 views
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
55 views
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. Ī½(CO) and Ī½(Fe-CO). And if there is, then ...
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55 views
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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1answer
58 views
pKa = pH for strong acid ā strong base?
I have learnt that for a weak acid ā 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 ā...
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2answers
42 views
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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55 views
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 teacherās argument is that it would indeed ...
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1answer
140 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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0answers
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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
47 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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1answer
24 views
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
35 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
24 views
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
Acidsāespecially weak acidsāwill give up their protons more readily if the concentration of > H3O+ in ...
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1answer
52 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
217 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
81 views
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 ...
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1answer
486 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
74 views
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
85 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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0answers
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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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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
176 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
72 views
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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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 ...
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1answer
104 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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0answers
35 views
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 ...
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2answers
74 views
Finding the pH of the resultant solution when a pH1 solution mixed with a pH2 solution [closed]
I want to know that is it possible that a $\mathrm{pH_1}$ solution mixed with a $\mathrm{pH_2}$ solution and the mixture would be less than $\mathrm{pH_1}$?
Is it possible that the result has a lower $...
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4answers
385 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{...
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2answers
122 views
Can we determine pH of liquid at home without pH-meter or litmus paper? [closed]
Are there alternative ways to determine $\mathrm{pH}$ of a liquid without using $\mathrm{pH}$-meter or litmus paper? In case if we didn't cook the liquid ourselves and don't know concentration of acid ...
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1answer
112 views
What the difference in data if calibrate pH-meter with 2 and 3 solutions? [closed]
pH-meter (12 bucks one) can be calibrated with 2 different solutions (let's say 4.0 and 6.86), but as an option 3 can be used (4.0, 6.86 and 9.18). If I use 2 instead of 3, what error I'm going to get....
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1answer
43 views
Calculating dissociation constant at different pKw values
What are the standard approaches to calculating how dissociation constants for acids and bases, $\mathrm{p}K_\mathrm{a}$ and $\mathrm{p}K_\mathrm{b}$, change as the ionic product of water, $\mathrm{p}...
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1answer
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Does Genistein remain in resonance stabilised form in physiological pH or acidic pH? [closed]
As a follow up, does the Carbonyl group at 4 position group get deprotonated or Hydroxyl group at 5 position get deprotonated? How does the resonance structure look? I have been looking through ...
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1answer
55 views
When is a buffer solution considered efficient?
By this I mean what is the rigorous definition of a buffer solution?
I know that a buffer is a solution able to resist changes of $\mathrm{pH}$, but how much resistance to $\mathrm{pH}$ does a ...
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1answer
54 views
How much NaOH I have to add to increase pH?
I'm stuck in solving this problem. I have two solution of $\pu{5 M}$ $\ce{H2SO4}$ that needs two consequential $\mathrm{pH}$ increasing: the first from the natural $\mathrm{pH}$ of $\pu{5 M}$ $\ce{...
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1answer
52 views
Is it possible to graph the equivalence of p[Cu²āŗ] with pH?
In no way I am a chemistry major, so please forgive me if my question seems stupid. I just need a way to find the "equivalent $\mathrm{pH}$" of $\mathrm p[\ce{Cu^2+}]$ if that makes any sense to you.
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3answers
194 views
Is pK_{In} = pH at equivalence point still true for weak basic organic indicators?
I am reading Ostwald Theory of Titration which says that indicators are organic weak acids or bases.
To prove the relation that $\mathrm{p}K_\mathrm{In} = \mathrm{pH}$, the textbook uses the following ...
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2answers
119 views
What actually happens in strong acid- weak base reactions?
I'm going back through my notes from a chemistry class, which I did well in despite not having a very good conceptual understanding, in order to hopefully develop that understanding, but there's ...
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2answers
103 views
How does pH depend on temperature, when taking into account volume expansion?
Since autodissociation of water is endothermic, increasing the temperature will drive the following equilibrium to the right, which has the effect of increasing $[\ce{H+}]$:
$$\ce{H2O <=> H+ + ...
