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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Can a multimeter be used to measure PH?

I would like to feed my garden a solution of water and Trisodium Phosphate (TSP), but I am uncertain of the correct amount of TSP to water ratio. Too acidic or too basic of a solution can harm my ...
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dilution and pH and pOH

The question is: given a $10$ ml solution with pH = $12.3$, which is then diluted to a $100$ ml solution, find the pH of the new solution. My attempt was as follows: [H$_3$O$^+$] = $10^{-12.3}$, and $...
Martin Westin's user avatar
3 votes
1 answer
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Are there LCMS compatible buffer systems available for the high pH range 12-14?

I want to perform chemical stability studies for different pH Values. To achieve pH Values from 1 to 6 I can prepare solutions with trifluoric acid and formic acid and ammonium formate and acetate. I ...
raptorlane's user avatar
-4 votes
1 answer
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At 80°C a solution having pH = 7 is? [closed]

When I came across this question I couldn't understand whether, they are asking the nature of solution at 25°C which has pH = 7 at 80°C or nature of solution at 80°C which has pH = 7 at 25°C ? ...
Rohit P L's user avatar
2 votes
4 answers
129 views

How can the Kw of water be constant?

I know in neutral solution, $\ce{[H+]}= \ce{[OH-]}= \pu{1.0 x 10^-7}$. However, let’s say I add an acid like HCl. This will increase $\ce{[H+]}$, therefore it’s no longer $\pu{1.0 x 10^-7}$, but is ...
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pH calculation of HCOOH +plus HCl solution

Question - What volume of $0.1 \ce{M}$ $\ce{HCl}$ solution should be added to a $\ce{500 mL}$ of $\ce{0.5 M }$ $\ce{HCOOH }$ solution in order to prepare an acid solution of $\text{pH}$ =$1.5.$ $K_a$...
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Can pure hydronium exist?

Can pure hydronium exist? If not, why not? It seems to me (and I am no chemistry expert) like pure hydronium should have the theoretical maximum acidity or minimum pH that a substance can reach. Can't,...
Alexei Rothschild's user avatar
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Dissolution of CO2 over time in a high pH solution

I asked this question in the biology stack-exchange but thought it might be more appropriate here. I am running a batch experiment using penicillin bottles where I have bacteria growing for 21 days in ...
Franco Grosso's user avatar
4 votes
1 answer
566 views

Possible technique for measuring pH in solutions

I would like to develop a device that measures pH in aqueous solutions. I'm not a chemist, but I have some basic knowledge about electrochemistry. So, I thought I could use two electrodes quite close ...
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Why is pH the most commonly known acidity scale when there are more intuitive ones?

Consider the switch from $$\operatorname{pH} = -\log_{10}\left(\left[\ce{H3O+}\right]\right)$$ to $$\operatorname{acidity} = +\log_{10}\left(\frac{\left[\ce{H3O+}\right]}{\left[\ce{OH-}\right]}\right)$...
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Anthoncyanins and its maximum absorbance value

Why does maximum absorbance occur for Anthocyanins at the 500 ~ 600nm range. Additionally how can one explain the high absorbance at lower pH for anthocyanins compared to higher pH values ?
Aurora Borealis's user avatar
2 votes
1 answer
264 views

How to correct for acidic water when taking the pH of a soil/water solution?

I work in a soil science lab and not very much a chemist. Recently I took the $\mathrm{pH}$ of a large number of soil samples using a glass electrode on a mixture of $\pu{10 g}$ soil and $\pu{20 mL}$ ...
Tillandsia123's user avatar
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1 answer
78 views

Creating Chloramines

I'm currently conducting some testing related to indoor pool environments. Here I believe, airborne chloramines are responsible for stress corrosion cracking in austenitic stainless steels. ...
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2 answers
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Why would my pH meter have changed its voltage setpoints?

I'm using a Thermo Scientific Orion Dual Star pH/ISE Dual Channel Benchtop Meter. The manual says that a $\mathrm{pH}~7$ buffer should read about $\pu{0 mV},$ and a $\mathrm{pH}~4$ buffer should read ...
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Calculate the pH of a buffered solution after adding strong acid [closed]

Calculate the pH of a solution formed by the addition of $0.0020$ moles of $\ce{HCl}$ to $\pu{100.0 mL}$ of $\pu{0.200 M}$ $\ce{CH3NH2}$/ $\ce{0.100 M CH3NH3Cl}$. $K_\mathrm{b}(\ce{CH3NH2})=4.4\times ...
Shoes's user avatar
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Why my mineral water from different sources do not mixed well? [closed]

Background: In 8 hours range, I have bought cold mineral water (brand A), then refill the plastic bottle with cold mineral water (brand B) from my office. As far i know, brand B has high pH while ...
Yukha Dharmeswara's user avatar
1 vote
0 answers
169 views

Determine the pKa of a diprotic acid by titration (if pKa1 is similar to pKa2)

Determining the acidity constants of a diprotic acid (in my case, tartaric acid) by titration with NaOH and pH-meter is not possible if pKa2 - pKa1 < 2. This is because there are no "pH jumps&...
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How to calculate pH of a 0.1 M solution of ammonium bicarbonate considering simultaneous equilibrium along with hydrolysis?

We need to calculate the $\ce{[H+]}$ of 0.1M $\ce{(NH4+)(HCO3^-)}$ given the $\ce{k_b(NH4OH), k_{a_1}(H2CO3), k_{a_2}(HCO3^-)}$ The hint tells me to directly use the result $\ce{[H+]=\sqrt{k_{a_1}(\...
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pH of a mixture of a weak acid and a different (non-conjugate) weak base

Let's say I have 1000 ml 1 M acetic acid ($\mathrm{p}K_\mathrm{a}$ = 4.76) and add 1000 ml 1M aniline ($\mathrm{p}K_\mathrm{aH}$ = 4.65). To what proportion is aniline protonated? 1M acetic acid has a ...
Lukas4235's user avatar
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1 answer
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Is the common way to calculate the pH of a solution with low concentration of acid wrong? [duplicate]

We had a chemistry test and one of the questions was this: What is the pH of $1,4^{-8} M$ $HCl$ in water? This is such a small amount of acid that you need to take into concideration the self ...
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How to find the added volume $V_e$

We have a volume $V_A$ of a solution of $\ce{CH3COOH}$ acid, its molar concentration is $C_A$ and it has $pH_0=3,4$, we add a volume of $V_e$ from distilled water to it, in this case it has $pH_0'=3,7$...
aymen aymen's user avatar
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1 answer
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pH of a solution from mixed solution

I am not a chemistry student. I have a problem with my preserved food. I am afraid that the pH is not below 4.6 for it to safe to eat. I want to check the pH of the food but it has small amount of ...
Aji123's user avatar
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1 vote
1 answer
159 views

Henderson-Hasselbalch equation and degree of dissociation

Is it possible to evaluate the degree of dissociation in unbuffered solutions, through the Henderson-Hasselbalch equation? For example: place acetic acid in a sodium hydroxide solution. After the ...
Luckenberg's user avatar
6 votes
1 answer
103 views

How to explain the acidity difference between these β-diketones?

In DMSO, pentane‐2,4‐dione (1) and 1,3‐diphenylpropane‐1,3‐dione (2) possess nearly identical $\mathrm{p}K_\mathrm{a},$ whereas 1‐phenylbutane‐1,3‐dione (3) is almost 1 $\mathrm{p}K_\mathrm{a}$ unit ...
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1 answer
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pH and degree of dissociation of drugs

I have a doubt, i hope not so stupid. Suppose we consider a buffer solution of acetic acid/acetate at pH = pKa = 4.76 and we add aspirin (pKa = 3.5): given that the pH of the solution is higher than ...
Luckenberg's user avatar
-2 votes
2 answers
599 views

Influence of (activated) charcoal on water's pH

Does immersing (a) charcoal / (b) activated charcoal (both clean, no ash) into distillate water influences water's pH? If yes - in which direction - acidic or alkaline? If there is an influence - is ...
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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-...
Makeen's user avatar
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18 votes
2 answers
2k views

Why are some pH standard solutions 6.86 and 9.18?

I have calibrated pH sensors in the lab on several occasions and have used standards of 4.0, 7.0 and 10.0 usually. Recently I received a sensor and was tasked to calibrate it, but it requested ...
en_lorithai's user avatar
2 votes
0 answers
35 views

Water dissociation constant $K_w$ in vapour, or are there charges entities ($\ce{H3O+}$, $\ce{HO-}$,...) in water vapour?

When water is in vapour state, to which degree is there still some dissociation with the existence of charged species like $\ce{H3O+}$ and $\ce{HO-}$? (I would be interested by any reference to ...
The Quark's user avatar
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Even in an acidic solution with a pH equal to 0, there are only 1 mol/L H3O+ ions, while there are approx. 54 mol/L water molecules

I find this sentence in my high school chemistry book to be confusing: "Even in an acidic solution with a pH equal to 0, there are only 1 mol/L H3O+ ions, while there are approx. 54 mol/L water ...
Authentic Melody's user avatar
-2 votes
1 answer
117 views

What's the pH of a solution knowing only pKa, mass and volume? (no molecular mass known)

Is it possible to calculate the pH of a given solution knowing only the pKa (but not the structure of the acid, i. e. its molecular mass), its mass and the volume of the solution? E. g. What is the pH ...
nicolausc's user avatar
3 votes
1 answer
613 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 ...
CaptainAmerica Whyso's user avatar
3 votes
0 answers
57 views

Measuring [A-]/[HA-] with Buffer and Indicator

I'm very confused on how to calculate the [A-]/[HA] value, given the fact that my dilution series uses buffers at various pH values with the same indicator (supplied at the same concentration to each ...
Tyler Anderson's user avatar
2 votes
1 answer
97 views

Why is phosphine more acidic than ethylene?

Shouldn't ethylene should be more acidic? It has a C=C bond, so the density of electron cloud would be higher in the areas of the double bond while the C-H single bond have way less electron density. ...
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1 vote
1 answer
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Is ethylene more acidic than phosphine?

Yeah, it's straight forward. Is CH2=CH2 more acidic than PH3 or not? Why so or why not? Any help or hint would be amazing. Thanks! PS: I think ethylene should be more acidic. It has a carbon-carbon ...
74H54N3's user avatar
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-3 votes
2 answers
711 views

How to determine the charge of amino acid at certain pH? [duplicate]

Problem What would charge would you expect on alanine when placed in a solution with a pH of 1.00? Answer Question Let's say I am given a certain pH of 2.00 rather than 1.00 for the "acidic ...
Lucia Keller's user avatar
-3 votes
1 answer
162 views

Should nitric acid be classified as a strong acid? Does it completely dissociate in water?

By definition, a strong acid must completely ionize in aqueous solution. However, in order to completely dissociate in water, strong acids must be more acidic than a hydronium ion and hence have a pKa ...
Malek's user avatar
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1 answer
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Effect of magnesium hydroxide MgOH formation in water on pH (Why more basic?)

Elemental magnesium reacts in (hot) water to form magnesium hydroxide and hydrogen gas: $$\ce{Mg_{(s)} + H2O_{(g)} -> Mg(OH)2_{(s)} + H2_{(g)}}$$ As indicated for example by phenolphthalein turning ...
Nikole's user avatar
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1 vote
0 answers
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Buffer solution of NaH2PO4 and Na2HPO4

We have this exercise without solutions From a 0.2 M $\ce{NaH2PO4}$ solution and a 0.2 M $\ce{Na2HPO4}$ solution, a buffer solution with pH = 6.8 is to be prepared. The total concentration of $\ce{...
wengen's user avatar
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-5 votes
1 answer
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Functional group for glycine that had being titrated (i) HCl (ii)NaOH

i am kinda confused with this question. They asked for the functional group of (i) glycine hydrochloride (ii) glycine that titrated with NaOH. I did take a look many times especially for glycine ...
Nku's user avatar
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1 answer
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Why should we not add the H+ ion conc coming from water before calculating pH of acidic/basic solution?

For eg: If we are calculating pH of the soln of a strong acid, we shall do this: pH= - log [H+] Where H+ is the concentration coming from that acid. Why shall we not add to this concentration, the H+ ...
Zeit Shpaga's user avatar
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1 answer
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Why doesn't the volume of NH3 = 325 ml in this problem? [closed]

I'm struggling with the problem below, and don't understand why A buffer solution with pH = 9.0 is to be prepared from a 0.2 M ammonia solution and a 0.15 M $\ce{HCl}$ solution. The sum of the molar ...
wengen's user avatar
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How to find the deprotonation percentage of an acid?

Given is an aqueous solution of mandelic acid (M = 152.2 g/mol; $pK_a$ = 3.4) with a molar concentration of 0.3 mol/ liter. A $\mathrm{pH}$ value of $2$ is measured for the aqueous mandelic acid ...
wengen's user avatar
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1 answer
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I tested the effect of temperature on the pH of carbonated water but the results seem to go opposite to what was expected. Could anyone explain?

We carried out an experiment to investigate the effect of temperature on the acid carbonate equilibrium in carbonated water. We tested 5 different temperatures (room temp, 2 above and 2 below) by ...
Renae Thompson's user avatar
1 vote
0 answers
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Making a reagent preparation simpler that requires pH adjustment

I have a basic question on a reagent (solution) preparation. Here are the steps that I take to prepare the reagent: Weigh the chemical (solid form, ammonium bicarbonate) and dissolve with DW to make ...
user129533's user avatar
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0 answers
38 views

Calculating acid volumes needed

I collect water quality samples used for irrigation. The samples are sent to a lab to measure $\ce{Ca^{2+}, Mg^{2+}, CO3^{2-}, HCO3^-}$, pH, and total dissolved solids. I need to use acid to prevent ...
sdabach's user avatar
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1 vote
1 answer
85 views

Is it possible to (naturally) change alkalinity without changing pH?

The Bjerrum plot shows how the different species of dissolved inorganic carbon (DIC) are distributed in sea water as a function of pH. The higher the pH, the more carbonate ion, less dissolved $\ce{...
ouranos's user avatar
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0 votes
3 answers
141 views

Is there a concise way to calculate pH of a solution after being diluted with water?

I do not have a chemistry degree or even much knowledge in the subject at all. I'm actually an auto detailer and this is why I have an interest in pH levels. All of our chemicals obviously have pH ...
Chris S.'s user avatar
1 vote
2 answers
313 views

How to calculate the pH value of a Carbonate solution?

I read the similar questions suggested when submitting my question but they didn't help me How can one calculate the pH of a solution? How to calculate pH of the Na2CO3 solution given ambiguous Ka ...
wengen's user avatar
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2 answers
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Purpose of a pH Problem

I was doing a multiple choice question as follows. The pH scale measures the Strength of an acid Concentration of hydrogen ions Strength of hydrogen ions Concentration of an acid The answer is 2 but ...
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