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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3 votes
0 answers
26 views

Assessing stability of protein used for interaction experiments after changing buffer from tris to HEPES

I have a protein with a theoretical $\mathrm{pI}~9.0$ currently stored in $\pu{25 mM}$ tris and $\pu{250 mM}$ $\ce{NaCl}$ $(\mathrm{pH}~8)$ at $\pu{−80 °C}.$ I need to do experiments in HEPES at $\...
-4 votes
0 answers
19 views

Phosphate buffer saline with different pH values [closed]

I would like to know with which reagent we can decrease the pH of the potassium phosphate buffer saline?
0 votes
2 answers
99 views

How does the concentration of H+ ions in HCl change as the pH changes? [closed]

I am helping my friend's 16 year old prepare for her GCSE chemistry exam. This question was on an AQA GCSE Chemistry past paper but I do not know the year and could not find a markscheme for it on the ...
25 votes
2 answers
13k views

Why does water dissociate to H3O+ and OH- rather than H+ and OH-?

Why does water dissociate to $\ce{H3O+ + OH-}$ instead of $\ce{H+ + OH-}$? This question came to surface when I was learning about acids and bases, and learned this definition: $\mathrm{pH=}-\log_{10}[...
0 votes
1 answer
36 views

What effect does the weak base have here?

Suppose we reacted enough strong base to fully neutralise a weak acid, clearly at this point (the equivalence point) the $pH$ would not be $7$. This is because the reaction between the strong base and ...
-2 votes
1 answer
44 views

Hydrolysis of $A_3B$ type weak acid-weak base salt

I know the formulae for weak acid-weak base salt of AB type. A peculiar question made me ask this. Do the formula for derived for AB type also hold for A3B type sal. For example: This is the question, ...
0 votes
1 answer
128 views

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 $\text{pH}$ =$1.5.$ $K_a$...
0 votes
0 answers
20 views

Proper batch adsorption mechanism for heavy metals

I'm a college student with scope on environmental science, specifically the adsorption of heavy metals in aquatic media. Currently, I suffered from serious issue of batch adsorption mechanism, which ...
0 votes
1 answer
57 views

Change in pH/acidity of vinegar after adding aqueous NaCl

There's a question in my (grade 10) textbook asking to determine what will happen to the pH/acidity of vinegar if a solution of sodium chloride in distilled water is added to it drop by drop. The ...
-5 votes
1 answer
71 views

Find the pH of a solution obtained by mixing 100 ml 0.1m Na3PO4 and 100 ml 0.1 M NaH2PO4. Given that H3PO4: [Κα₁ = 10^-4, Κα₂ = 10^-7, Каз = 10^-11] [closed]

So, my query is that since NaH2PO4 is a weak acid, and Na3PO4 is a basic salt, wouldn't they react? Another theory was that since NaH2PO4 is a weak acid and Na3PO4 is a salt of strong acid and NaH2PO4,...
1 vote
0 answers
25 views

Aquatic chemistry, pH and alkalinity

Hope you can help me with an aquatic chemistry question. I have different types of water of different pH and alkalinity. pH, alkalinity, HCO3 and CO2 concentrations are known. I need to calculate the ...
19 votes
1 answer
4k views

How can benzaldehyde have a pKa of 14.9?

There are numerous websites out there which claim that the pKa of benzaldehyde – C6H5CHO – is 14.90. (Just do a Google search for benzaldehyde pka to see what I ...
2 votes
1 answer
408 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 ...
2 votes
0 answers
42 views

Alternative pH sensing methods?

I am looking for alternative methods to measure the pH of water (swimming pools, tap water, rivers,...) with (ideally) the following properties: Durable: no maintenance or calibration required for 5-...
0 votes
0 answers
27 views

Does pH affect the activation energy of decomposition of hydrogen peroxide using iron (III) nitrate solution?

I know that pH can affect the activation energy of the decomposition of hydrogen peroxide when catalase is used, as catalase is an enzyme. However, if I use some nonenzymatic catalysts like iron (III) ...
2 votes
2 answers
86 views

How long can pH solution calibration be used for?

I am using a pH meter regularly (6 to 12 time per week), used mostly for home-food processing (mostly measuring the acidity of whey). The meter requires weekly calibration, which is quite time ...
3 votes
1 answer
163 views

Reading and adjusting pH of reverse osmosis water

I grow things for a living and regularly use pH meters + strips to read and adjust the pH of various nutrient and pesticide solutions. Oftentimes, I have a need for nearly naked water with the pH ...
0 votes
1 answer
42 views

Finding the pH level of a liquid process

A photo of 15ml of distilled water accompanied with 3 drops of both universal indicator and bromothymol blue were mixed together and taken (white background was put into the back of the beake). The ...
-2 votes
1 answer
76 views

Mass of gaseous ammonia required to prepare ammonia solution of a given pH

How many grams of gaseous ammonia do you need to make $\pu{200 mL}$ aqueous ammonia solution with $\mathrm{pH} = 11.34?$ As the mole ratio is the same for $\ce{H+}$ and $\ce{NH3},$ $$\ce{NH3 + H+ -&...
0 votes
2 answers
139 views

Can carbonic acid form a salt with pH < 7?

Please read edit before answering Background I am currently studying in 10th grade. This question appeared in my science exam - Which acid does not form an acidic salt? Phosphoric acid Carbonic acid ...
9 votes
1 answer
7k views

Why does saline have a pH of 5.5?

I am a physician and administer 0.9% NaCl in water ("normal saline") to patients frequently. The bag says it has a pH of 5.5 (compared to the human body of 7.4). I am asking why the pH is so low. It ...
0 votes
1 answer
408 views

How can I calculate the pH of the solution created by reacting sodium with water?

$\pu{23mg}$ of sodium was added to $\pu{100cm3}$ of water. What is the pH of the solution produced? $$\ce{2Na + 2H2O -> H2 + 2NaOH}$$ So firstly to find the moles, I've divided $\pu{0....
6 votes
2 answers
191 views

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 ...
1 vote
0 answers
78 views

How do you calculate the pH range for which one metal precipitates but the other stays in solution?

The problem I have been asked to solve is: $\ce{Cd^2+}$ and $\ce{Fe^2+}$ (starting concentration $\pu{E-3 mol/L}$) should be separated by precipitation using $\ce{H2S}$. Does a pH range exist ...
2 votes
1 answer
2k views

Does gold always become gold chloride when dissolved with HCl and an oxidizer and can it always be precipitated with sodium metabisulfate?

I tried to extract gold from computer parts by STRIPPING the gold using $\ce{HCl}$ and $\ce{H2O2}$ by dissolving the copper & nickel underneath but i added FAR too much $\ce{H2O2}$ by a stupid ...
-4 votes
1 answer
60 views

Is it possible to make acids and bases in amphiprotic solvents other than water [closed]

In such solvents, could there be chemicals which could donate/accept protons, and if so could their solutions display acidic/basic properties?
1 vote
0 answers
31 views

How to calculate the pH of a mixture of an acid with a buffered solution?

Being a physicist by training, having worked in software development for the last 10 years. Having heard my last chemistry lecture 15 years a go I am a bit lost in regards to how one can calculate the ...
-3 votes
2 answers
200 views

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 ...
0 votes
2 answers
137 views

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 $...
3 votes
1 answer
135 views

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 ...
7 votes
2 answers
889 views

Numerically solving chemical equilibrium equations

Here are chemical equilibrium equations: $\begin{cases} \mathbf{N}^\text{T}\mathbf{X}+\mathbf{C}=\mathbf{Y}\\ \mathbf{N}\ln\mathbf{Y}=\ln\mathbf{K} \end{cases}$ Here $\mathbf{C}=\begin{pmatrix}c_1\\...
-4 votes
1 answer
159 views

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 ? ...
2 votes
4 answers
162 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 ...
-2 votes
3 answers
437 views

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,...
-1 votes
2 answers
156 views

Calcium-containing acidic solution

I want to prepare an acidic solution containing Ca ions. I thought about dissolving calcium sulphate, acetate or phosphate in $\pu{2 M}$ $\ce{H2SO4}$ or $\ce{H3PO4}$ solutions, but it seems that $\ce{...
6 votes
1 answer
1k views

Why is the aqueous solution of KMnO4 slightly basic?

This is in the context of the various changes in oxidation state the permangananate ion can undergo with the variation of the pH of the medium. Besides the cases of strongly basic and strongly acidic ...
0 votes
0 answers
50 views

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 ...
4 votes
1 answer
577 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 ...
-2 votes
1 answer
46 views

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 ?
3 votes
1 answer
96 views

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)$...
2 votes
1 answer
297 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 $\pu{20 mL}$ ...
-2 votes
1 answer
86 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. ...
4 votes
2 answers
112 views

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 ...
-2 votes
1 answer
78 views

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 ...
15 votes
4 answers
20k views

Is LiOH a weaker base than NaOH?

Is $\ce{LiOH}$ a weaker base than $\ce{NaOH}$? Note: I'm not interested in "why," but rather what the "real" $\mathrm{p}K_ \mathrm{b}$ values are. $$ \begin{array}{lcc} \text{Data for Alkali Metal ...
-2 votes
1 answer
90 views

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 ...
1 vote
2 answers
3k views

The effect of pH and solubility on coagulation in water treatment

In water treatment, a specific pH range must be met in order for the process of coagulation to occur properly. Sources have stated this is due to the pH affecting the solubility of the coagulant, but ...
3 votes
1 answer
522 views

Calculate pH of imidazole in solution

I am having trouble understanding how to know how a molecule will reaction in solution. For example, if I have $\pu{1 M}$ of imidazole in solution, how can I calculate the pH of the solution by only ...
6 votes
4 answers
10k views

How is seawater alkaline?

If when water and carbon dioxide react they form carbonic acid, carbonate, and bicarbonate, how does seawater still have a pH of around 8? Doesn't a compound need an hydroxide ion to be a base?
1 vote
0 answers
352 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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