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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 to calculate the pH of the neutralisation of HCN with excess of KOH?

Write the reaction between $\pu{0.05 mol}$ $\ce{HCN (aq)}$ and $\pu{0.08 mol}$ $\ce{KOH (aq)}$ with $V = \pu{500 mL}$ and then calculate the pH. So I wrote the reaction: $$\ce{HCN (aq) + KOH (aq) &...
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1answer
96 views

Is change of pH of water with respect to temperature linear?

Only recently I learned that the pH of water varies with temperature, from about 7.47 at 0 °C to 6.14 at 100 °C. My question is, first, is there a geometric explanation for this, in the sense that ...
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385 views

How to calculate resulting pH of mixing 2 fruit juices [closed]

I want to make jelly from a mixture of 50% fresh apple juice and 50% juice of another fruit. The resulting pH must be less than 4.6, otherwise the jelly will not be safe from C. botulinum. Based on ...
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1answer
221 views

Aluminium sulphate solubility as function of the pH

earlier I asked about how to know the aluminium sulfate solubility as function of the ph (see the previous question here). I found this diagram on the page 57 of Rubin, A. J., & Hayden, P. L. (...
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1answer
182 views

How to know the aluminium sulfate solubility as function of the pH?

I'm trying to find a diagram or a reference for to know the solubility of aluminium sulfate $\mathrm{Al_{2}(SO_{4})_{3}}$ in differents pH values. Something like:
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1answer
2k views

pH value of a buffer solution of HClO and NaClO [closed]

So, I have 200mL of HClO 0,64M. I mix it with 0,1mol of NaClO. How should I calculate the pH? My question is about this: should I keep attention about changes made to the solution volume after adding ...
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96 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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pH at different concentrations

In making gummies with pectin, the pH is very important and needs to be at or below 3.4. USP indicates dissolving it in a 10% solution to test the pH, while some use a 50% solution. I'm told the ...
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1answer
115 views

How do the pKa and pH indicate to the proper environment of protonation?

I have been reading an abstract of a paper for a couple of minutes (reference below) but I cannot understand a piece of it. The abstract: The ionization state and $\mathrm pK_\mathrm a$ of the ...
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31 views

Building a proton pump for aqueos solution with suitable membrane and electricity?

I know the pH effect during electrolysis ( Effect of pH on electrolysis) and i wonder if it could be used in combination with a membrane (e.g. Nefion DuPont) to build a "proton pump". I need i slight ...
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Can buffers regulate the pH, or do they just smooth out pH bumps?

Hydrogen carbonate can react with hydrogen ions to create carbonic acid which degrades into water and carbon dioxide that can be exhaled or excreted otherwise. That lowers the pH, yes. However, in ...
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94 views

Which formula to use to find the pH of a solution? [closed]

I just had my first exam yesterday, and I'm always tripped with this question that combines neutralization with buffer solution. The task is to find the pH. I did try to understand the general concept ...
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127 views

How to make an alkaline wax mixture?

I want to treat a wax so that it has an alkaline pH of at least 10. I tried just mixing sodium hydroxide with beeswax but the sodium hydroxide reacted with the beeswax and changed its properties. I ...
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1answer
60 views

Effect of the pH on the synthesized nanoparticles [closed]

I have synthesized gold nanoparticles in water through the seed-mediated thermal method by cationic additive $\ce{Ag+}$ as an assisted growth procedure [article]. The pH of the nanoparticles solution ...
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1answer
47 views

Concentration of Carbon dioxide in Blood

Let's say we're able to decrease concentration of carbon dioxide in blood, how will the pH of the blood be affected? My Reasoning : Since blood has approximately 92% water, it is safe to assume the ...
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1answer
504 views

Find increase in OH- ion concentration after base is added

The pH of a solution is 7.00. To this solution sufficient base is added to increase the pH to 12.0. the increase $\ce{OH-}$ ion concentration is: (A) $5$ times (B) $1000$ times (C) $10^5$ ...
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2answers
336 views

What is the pH of HCl solution at $10^{-8}$M? [duplicate]

After using the negative logarithmic value of $\ce{H^+}$ ion concentration, I get a value of pH that results in base. Can you please help me? Thank you in advance
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448 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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1answer
1k views

Which compound or compounds are responsible for color change in blue butterfly pea flower tea?

Blue Butterfly Pea flower tea is blue by default. Add citrus juice and it turns purple. What compound or compounds are responsible for this reaction to change in pH? Wikipedia doesn't say, nor can I ...
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0answers
22 views

Determining pH of immunoprecipitation buffer recipe

I'm following a protocol for extraction of proteins from yeast, and I came across this recipe for immunoprecipitation buffer: $\pu{50 mM}$ HEPES-$\ce{KOH}$, pH 6.8, $\pu{150 mM}$ $\ce{KOAc}$, $\pu{...
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1answer
2k views

pH of an amino acid solution

I'm trying to help a friend of mine with this chemistry question: What is the pH of a $1.0M$ solution of glycine? They're given that the pKa of COOH is $2.4$ and the pKa of the amine group is 9.6. ...
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166 views

pH-value of a multicomponent buffer [closed]

We are trying to predict the pH-value of a multicomponent buffer. It consists of: \begin{array}{lcrr} \# &\text{Component} &C,\,\pu{mol L-1} &\mathrm{p}K_\mathrm{a1} &\mathrm{p}K_\...
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Determining the acid dissociation constant change with temperature in sparkling water

I already have the different values of pH at the different temperatures, but what I'm trying to figure out is obtaining the acid dissociation constant using these pH values. Is there a way I can do ...
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2answers
879 views

pH of dilute acids in hexane

Consider a strong acid $\ce{HA}$. In a $\pu{1000 mL}$ of hexane (assume it is unable to accept a proton) we "dissolve" (this can mean forming a suspension with vigorous stirring - otherwise we can use ...
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Chemistry behind lip balm coloring based on skin pH

I stumbled across an ad for a clear, colorless lip balm that purportedly tints your lips a shade of pink determined by your skin's pH. This balm stain applies on clear then reacts with your skin's ...
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1answer
874 views

What are the side effects of adding dry ice to a swimming pool?

My apartment complex pool was closed today due to a resident dumping a large quantity of dry ice into the pool. In the notification from my landlord, they stated: Dry ice is frozen carbon dioxide ...
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2answers
599 views

Which definition of Acids and Bases conforms to the pH scale?

It's all in the title. Is it the Arrhenius or the Brønsted-Lowry definition? Or is it some other definition? Also, our teacher told us that $pH$ stands for "Power of Hydrogen", but some sources say ...
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56 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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0answers
338 views

How does acid damage skin? [closed]

As I understand it, acids are substances which have a high concentration of H+ ion which makes acid an acid. When interacting with our skin, acid can damage it. How does this concentration of protons ...
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1answer
514 views

Why would the pH of a solution not be 7 at the equivalence point of an acid-base titration? [duplicate]

Is it because the new substance formed might be acidic/basic ? The internet defines this point as when the number of moles of the acid equals the number of moles of the base. But if we have for ...
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1answer
72 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{...
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Will an aqueous sodium hydroxide solution degrade over time?

I have a chiller bath, which is attached to a 150 ton cooling unit through 4" PVC pipe. The bath itself holds around 5000 gallons of water, and is made of 304 stainless steel. It constantly circulates ...
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3answers
924 views

How do the numbers on the pH scale compare? [closed]

How do the numbers on the pH scale compare? Example – is a pH of 4 twice as strong as a pH of 2? Remember the pH scale is not linear! Also, "is 4 twice of 2" isn't my question. I just want to know the ...
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92 views

Wondering how I should have graded this question (freshman lab, about buffer capacity)

I TA the intro freshman lab course. In a lab about buffers and buffer capacity, the students were instructed to make 50 mL of a 0.1 total molar pH 6.70 buffer by dissolving solid $ KH_2PO_4 $ and $ ...
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2answers
491 views

Bicarbonate decomposition and pKa [closed]

I want to understand why the p$K_{\mathrm a}$ of $\ce{HCO3-}$ is approximately 10.2 and not less. My hypothesis is this : Bicarbonate could react in two ways in an aqueous solution: $[1]\qquad\ce{...
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41 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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1answer
183 views

Could we reach a pH of 4.9 by blowing through straws?

According to Wikipedia's article on Breathing: The permanent gases in gas we exhale are 4% to 5% by volume more carbon dioxide and 4% to 5% by volume less oxygen than was inhaled. If I started ...
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3k views

Calculating concentration of H+ Ions using Ka Value [closed]

I have this homework question that I am a bit stuck on for an answer. If anyone could help that would be great. Question: For a $\pu{0.2M}$ $\ce{HNO2}$ solution ($\pu{K_a= 4.5 \times 10^{-4}}$) ...
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1answer
88 views

Why isn't there a third buffering zone in the pH curve of this titration?

I'm in chem 30 right now and we were learning about pH curves and buffering zones. I was looking at a question on the titration of $\ce{H3PO4}$ with $\ce{NaOH}$. The curve showed two qualitative ...
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1answer
706 views

Why doesn't a neutral solution at any temperature have pH 7?

I am given 4 statements to choose from and find which is correct about a neutral solution: $K_\mathrm{w} = \pu{1.00\times10^-14 mol^2 dm^{-6}}$ The solution contains only $\ce{H2O}$ $\ce{[H+] = [OH-]...
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How much citric acid do I need to add to bring pH down from 4.8 to 4.2?

It has been a number of years since I did chemistry calculations. I would like to know how much citric acid (powdered form - assuming it is 100% anhydrous) to add to a food product to reduce the pH ...
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3answers
76 views

Finding ions in water samples

So for a school chemistry assignment I was given 5 water samples and a bunch of different reagents to help me find out what was in the solutions. I'm stuck on two. The first one had a pH of 7 and ...
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1answer
835 views

Calculating pH of solution of phosphoric acid and ammonia

What is the $\ce{pH}$ of the solution created when $\ce{50ml}$ of $\ce{0.2M}$ $\ce{H3PO4}$ is mixed with $\ce{50ml}$ of $\ce{0.4M}$ $\ce{NH3}$? This problem can be approached rigorously. That's what ...
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What is causing the buffer region in a weak acid - strong base titration?

For the buffer region in this, why does it stop the pH from increasing? At the start: $$\ce{CH3COOH + NaOH -> CH3COONa + H2O}$$ Which means there will be a high amount of salt in the solution, ...
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1answer
267 views

Litmus paper reactions for mixed solutions [closed]

I am wondering what could cause my litmus paper to first react to the alkaline. turning blue, and then changing to an acidic red color?
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1answer
292 views

Acid-Base buffer question

Calculate the change in pH of a buffer made by combining $\pu{500 ml}$ of $\pu{0.1 M}$ $\ce{CH_3CH_2COOH}$ and $\pu{500 ml}$ of $\ce{CH_3CH_2COONa}$, when $0.04$ moles of $\ce{NaOH}$ is added to the ...
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1answer
46 views

Am I solving this pH problem correctly?

A liter of a solution contains $\pu{0.120 mol}$ of $\ce{C6H5COOH}$ $(K_a = 6.5 ×10^{-5})$ and $\pu{0.105 mol}$ of $\ce{C6H5COONa}$. I'm asked to calculate the pH of the solution after adding $\pu{100 ...
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395 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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429 views

pH level in human body [closed]

For my alkaline diet, I need to maintain a pH that's above 7, I need to achieve the objective like this: I have eaten 300 g of grapefruit (pH = 13), and eaten 70 g of chocolate (pH = 5,5). What pH ...
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87 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 ...