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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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\\...
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What pH value of 1M sodium crotonate solution supposed to be?

I need to prepare the $\pu{1M}$ solution of sodium crotonate, however, I don't have one in lab, but I do have sodium hydroxide and crotonic acid. Thus, I calculated that for $\pu{100 mL}$ of $\pu{1M}$ ...
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354 views

Why does pKw first decrease but eventually increase when temperature rises?

I understand the initial decrease in pKw. $\ce{Heat + H2O (l) <=> H+ (aq) + OH- (aq)}$ Temperature increases, reaction shifts to the right, so $\ce{H+} \text{ and } \ce{OH}$ ...
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135 views

Slow acidification process

I'm trying to find a substitute of Glucono delta-lactone (GDL). This food additive is usually used to produce silk tofu. Because of its slow hydrolysis the pH decreases very smoothly, which results in ...
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54 views

Decomposition of Hydrogen Peroxide Catalysed by Potassium Iodide in Basic Solution

As part of my high school project, I had to measure the initial rate of decomposition of hydrogen peroxide catalysed by potassium iodide at different pHs. At higher pHs (alkaline conditions), I found ...
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117 views

Why is the experimental pH of vinegar (acetic acid) so much higher than expected?

I bought some sodium hydroxide on Amazon and went about titrating solutions I make with it. As I'm an amateur chemist at home, I have limited tools. A pad of paper, some 5% acetic acid vinegar, and ...
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139 views

Naming convention for buffer solutions/systems

Is there an official naming convention to follow for buffer solutions/systems? I've noticed that the name of the buffer usually just follows the name of the salt (ex. sodium acetate buffer), but what ...
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92 views

Calculating the ionic strength of a histidine solution

I'm trying to repeat the calculation of the ionic strength of a solution containing histidine as a buffer I recently read in a paper. In their paper, the authors calculate the ionic strength of a 20 ...
3
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0answers
31 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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77 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 ...
3
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74 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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112 views

How can I preserve chlorophyll for long periods of time?

I'm currently working on a XIX century photographic process called Anthotype. It relies on organic colored substances that fade when exposed to sunlight. For the substances I've tried alcoholic ...
3
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514 views

What pH indicators are commonly used for non-polar medium?

Compounds, commonly used as pH-indicators, are soluble in aqueous media and polar solvents (DMSO, DMF, NMP etc.) and are functional pretty much across all these solvents. However, practically none ...
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201 views

How much hydrolysis will likely occur of the following bonds at pH 1-4 in the time period of 1-3 hours?

The bonds are: (I have given pictures of what I mean in case there's any ambiguity that I leave open in these questions. Also so that if you want to number the R groups you've got a head-start) ...
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3answers
901 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 $...
3
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1answer
272 views

Finding concentration and moles given final and initial pH

Questions: How many moles of $\ce{NaOH}$ are needed to change $500~\mathrm{L}$ of solution with $\mathrm{pH}\ 2$ to $\mathrm{pH}\ 11$? A swimming pool contains 2 million litres of water at $\mathrm{...
3
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1answer
2k views

Find the concentration of the HCl solution when mixed with 1.265g of ACES-K+

$\pu{1.265 g}$ of N-(2-acetamido)-2-aminoethanesulfonic acid potassium salt ($\ce{ACES^-K+}$, $M=\pu{220.29 g/mol}$) is dissolved in $\pu{88.42 mL}$ of water. $\pu{27.59 mL}$ of $\ce{HCl}$ is added to ...
3
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1answer
248 views

Positive charge on a zwitter ion at pH=7?

I faced this question. But I am having some problems understanding the solution to this: How can the negative charge on the peptide vanish on $\pu{pH = 7}$? Suppose, we have some $\ce{H+}$ donor on ...
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60 views

How to compute a needed volume of solution to adjust to a target pH

I am a software engineer and I would like to solve a chemistry problem. I have revised the subject a bit to understand the basics :) My goal is to maintain a constant pH of a water tank (tap water). I ...
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21 views

DEG monobutyl ether pH change

We are using DEG monobutyl ether (CAS 112-34-5) in our production. Normally it is pH neutral, however suddenly we noticed that it has shifted to being acidic (pH=3.4). What has changed in the material?...
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306 views

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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58 views

The pH of a drop of water containing ammonia

Presented with the following equations: What would the $\mathrm{pH}$ of a drop of water be, while in equilibrium with $\ce{NH3(g)}$ at a concentration of $\pu{150 ppb}$? $$\ce{NH3_{(g)} + H2O_{(l)} &...
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59 views

Hydrochloric acid substitute in an Iron-gall ink solution

Recently I started experimenting with making my own ink to be used in fountain pens. I was wondering if hydrochloric acid in an iron-gall ink is used to prevent sediment ONLY by lowering the pH of ...
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33 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 ...
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122 views

How does a pH glass electrode work?

Every source I read mentions the potential difference building up at the glass membrane (according to the Nernst equation). But how is this difference actually measured? Sticking an electrode into a ...
2
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1answer
176 views

Why is the pH level of carbonation loss decreasing then increases afterwards?

We have done an experiment of the titration of unsealed sprite soda to find the amount of carbonic acid being loss on various duration (0 to 1 hour), due to decrease pressure. The calculation was to ...
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70 views

Water values and water hardness

We have drinking water with the following values: Calcium mg/l 62.7 Magnesium mg/l 10.3 total hardness 7.) dH 11.1 Total hardness 7) mmol/l CaCO3 1,99 Carbonate hardness °dH 8.5 Hydrogen ion ...
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272 views

Alternatives to EDTA for calcium ion chelation

Are there any $\ce{Ca^2+}$ chelating agents (other than EDTA) that are as good as EDTA in terms of binding calcium ions and effective in a pH range of $5$ to $9$?
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582 views

Relationship of CO2 in water

We have an evaporative cooling system here at the power plant that uses city water. The water is pumped up and cascades down across a filter media cooling the intake air to the gas turbine. This is ...
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68 views

How fast does atmospheric carbon dioxide dissolve into strongly basic solution?

I'm conducting some pH measurements with solutions containing NaOH and I'm a bit concerned that carbon dioxide will dissolve and affect my measurements by lowering the pH according to the reaction: $$\...
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46 views

How to determine concentration limits of a buffer that's limited by solubility?

I need to maintain a certain range of % of ionisation from a buffer. For e.g. Histidine buffer. When making high concentration of this buffer at (say) pH 7.2, 25'C, [concentration] is limited to 75mM ...
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596 views

Potassium phosphate buffer + EDTA

Given 10 mM potassium phosphate buffer (pH = 7.0), 50 mM potassium propionate and 20 mM EDTA (acid). After addition of all 3 components pH becomes 4 since EDTA has 4 $\ce{OH}$ groups. How to ...
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165 views

Why is it difficult to measure the pH of environmental water samples accurately (near 7)?

I've read in several places (edit: 1, 2, 3, 4, 5, 6, 7, 8. 9, 10, 11, 12) that there are many practical factors that make accurate pH measurements of roughly neutral environmental water samples more ...
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101 views

How to slow/prevent corrosion of a steel post

I have a steel post set in limestone, about 18-20 inches deep, with some concrete around it. I just noticed that I have about 6 inches of water inside the post. The limestone had a small seam in it ...
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830 views

How does increasing ionic strength affect the pH of solution?

I'm having trouble interpreting the data for an experiment. With increasing ionic strength, I found lower solubility but also lower pH of the solution. What is the effect of the ionic strength on the ...
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0answers
646 views

Does water acidity affect sugar solubility?

For example, when making lemonade: will mixing sugar in water after adding lemon juice lead to a slower sugar dissolving rate, than if sugar were mixed in before adding lemon juice?
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681 views

Calculating the pH of buffer solution made of two salts of a polyprotic acid

When we are making a buffer solution by solutions of a weak acid and its salt like $\ce{CH3COOH}$ and $\ce{CH3COONa}$, or by a weak base and its salt like $\ce{NH3}$ and $\ce{NH4Cl}$, we can use the ...
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0answers
84 views

pH and solute solubility in waste mixed water

I was reading a module on waste management. There were two interesting points. High pH results in higher solubility of $\ce{CN-}$. I understand that for HCN: $$\ce{HCN ->H+ + CN-}$$ Higher pH ...
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0answers
39 views

Effect of protein hydrophobicity on metal interaction

I'm studying how metals and proteins interact (metal-protein complexes). I've found that almost all proteins could bind with metal at higher $\mathrm{pH}$ values, but also found some proteins showed ...
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51 views

pH, conc vs activity

After studying a somewhat overview of "gamma" activity coefficient (it is not actually in our course but may come in exam as a part of unknown paragraph in ionic equilibrium) I can understand most ...
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0answers
127 views

How to calculate concentrations when dissolving two salts?

Some solid silver bromate was dissolved together with solid silver acetate what would be the highest achievable pH? \begin{align} K_\mathrm{sp}(\ce{AgBrO3}) &= 5.38 \times 10^{-5}\\ K_\mathrm{sp}...
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677 views

Buffer capacity of different types of milk

Currently I am tasked with designing an experiment that that I will have to perform in 2-4 weeks, but I don't have to decide on on a topic soon. I was thinking of performing an acidometric titration (...
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775 views

pH meter and paraformaldehyde

We have had an ongoing debate in our lab and several bad pH electrodes. I would like to ask the following question Do paraformaldehyde soloutions (2-4% w/v) damage pH meter electrodes? If so, why?
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109 views

Isoelectric point pH, mV, for a metal oxide nanopowder

I'm trying to make a solution of $\ce{TiO2}$ that will coat stuff in as dense a monolayer as possible. To do so, I'm using nano sized $\ce{TiO}$ particles and trying to get them to get as close to ...
2
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1answer
716 views

pKa of Tris corrected for ionic strength

I have a question regarding the molar fraction calculation of Tris buffer at different temperatures. Tris dissociates according to the following equation: $$\ce{Tris + H2O -> Tris+ + OH-}$$ So, ...
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22 views

Comparing acidity between 4-hydroxybenzaldehyde and 2-hydroxybenzaldehyde

https://hmdb.ca/metabolites/HMDB0011718 https://hmdb.ca/metabolites/HMDB0034170 The above two links provide the pKa values for the 4-hydroxybenzaldehyde (pKa = 7.32) and 2-hydroxybenzaldehyde (pKa = 8....
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Why are colloidal sol particles of acidic dyes negatively charged and basic dyes positively charged, when it should be the other way round?

From NCERT Class 12 Chemistry; Sri Aurobindo Marg, New Delhi, India; January 2019; p. 136: Colloidal solutions of basic dyes like methylene blue are positively charged whereas colloidal solutions of ...
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Chlorophyll content in relation to the pH of the solution in which it is boiled

What would be the expected trend of chlorophyll content in relation to the pH of the solution in which it is boiled? Would there be the least chlorophyll degradation in basic or neutral solutions? ...
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22 views

Cleaning solution alternatives for acetate, nitrate, or polyester base motion picture film

I am in search of alternative film cleaning solutions which are safe for the film, me, and the environment. I have used several different professional film cleaning solutions in my many years of ...
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0answers
53 views

Understanding the pH scale for edible food!

I'm working on a website where I want to provide the pH level of plants! Although i don't even know what this is (I have zero knowledge in chemistry), I have to provide it! What I want to do is ...