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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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3answers
575 views

Why does dissolving a salt in water get a high pH?

I dissolved some sodium carbonate in water and I measured the $\mathrm{pH}$. It turned out to be 11. I don't really understand why dissolving it in water increased the $\mathrm{pH}$. I mean, I know ...
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pH and materials selction [closed]

I working on the Navy study guide for their nuclear engineering programs and I am not a Chemist. Thus, I have come here to try and develop a better understanding of the subject matter. Why is pH ...
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95 views

Why are many chemical relationships logarithmic?

I've noticed that in many relationships in chemistry, one variable is linearly related to the logarithm of another. Why is this the case? For example, I carried out an experiment where the dependent ...
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2answers
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Is it true that a pH higher than the pKa of an acid make the H automatically disassociate?

Will the hydrogen atom always disassociate if the pH of the solution is higher than the pKa of the acid?
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1k 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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350 views

pH Curves for Titrations

Why does the pH rapidly increase near the equivalence point during--why does the slope of the graph of a pH curve sharply increase around this area?
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2k views

Calculations for making a buffer from a weak base and strong acid

How many moles of $\ce{HCl}$ must be added to $\pu{100 ml}$ of a $\pu{0.100 M}$ solution of methylamine ($\mathrm pK_\mathrm b = 3.36$) to give a buffer having a $\mathrm{pH}$ of $10.00$? (The answer ...
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1answer
164 views

Effect of pH on Dilution of HCl Solution

Q. A solution of $\ce{HCl}$ has a $\mathrm{pH}$ of $5$. If $1\ \mathrm{ml}$ is diluted to one litre of water at $\mathrm{pH}=7$. What is the $\mathrm{pH}$ of the resulting solution. Attempt- $$\...
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Does NaOH have a higher OH- concentration than NH3?

In my book it's a multiple choice question with only one correct answer. There are two solutions of $\ce{NaOH}$ and $\ce{NH_3}$ that have similar concentrations and volumes. These two are among ...
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Phenolphthalein as a indicator for the titration of benzoic acid

Question: Justify the use of phenolphthalein $(\mathrm{p}K_\ce{in}=9.4)$ as a indicator for the titration of benzoic acid $(K_\mathrm{a}=6.3\times 10^{-5})$ with $\ce{NaOH}$. My attempt: I can ...
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1answer
345 views

Mechanism of pseudo buffer pH maintenance

Some solutions, like concentrated HCl, act as buffers even though they lack the buffering component. What is the cause for such a behaviour?
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2answers
12k views

Caffeine dissolution

I am looking to add caffeine powder in pure form to water that has a pH level of 7 or higher. What would the pH level be if I do this? Is Caffeine itself acidic?
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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?
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Why will a strong acid neutralize as much base as a weak acid?

This is a simple concept that I can't seem to understand. Why will a strong acid neutralize as much base as a weak acid, if the acids are of the same volume and concentration? A strong acid will ...
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2answers
958 views

Can Henderson-Hasselbalch equation be used to determine the pH of a solution when a strong base and a strong salt of that base stay together?

The following problem I have stated was not given to me as a homework. I have found this one in my textbook. I have solved it in my own way, but I'm not sure about the correctness of my procedure. I ...
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2answers
26k views

How do I calculate how much sodium hydroxide I need to add to get a new pH?

A 100 ml $\ce{HCl}$ solution has a pH of $3.7$. You want the solution to be of pH 4.5. You have a solution of $10\ \mathrm M$ $\ce{NaOH}$. How much $\ce{NaOH}$ do you need to add to to the $100\ \...
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10k views

Solution for storing a glass electrode

What kind of storage solution is required for a glass electrode? Is 3 M $\ce{KCl}$ sufficient for this purpose? If so, what is the approximate pH of that solution (the solution I use presently has a ...
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2answers
7k views

About pH of an aqueous solution of SO2

Probably we can have an aqueous solution of $\ce{SO2}$ by dissolving it in water, because we would have an equilibrium between $\ce{SO2(g)}$ and $\ce{SO2(aq)}$: $$\ce{SO2(g) <=> SO2(aq)}$$ How ...
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788 views

Find amount of acid and base required to make buffer

I am wondering if it is possible to know exact amount of acid and base that we can put in together to make a buffer. I want to make a 0.05 M extraction buffer using disodium hydrogen phosphate (DHP) ...
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1answer
89 views

Figuring out the pH

So, I’m refreshing my college chemistry a bit. Could someone give me a pointer on the following practice exercise? What is the pH at 25 degrees Celsius in a bucket with 10 liter pure water in which a ...
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1answer
64 views

What could be causing noisy pH measurements?

I designed and built a hydroponics system with pH logging and I am trying to understand why pH measurements in the nutrient reservoir vary ~ ±0.2 pH while measurements in a separate bottle of probe ...
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1answer
92 views

Dissociation constants of leucine

Leucine is a type of amino acid. Let me write its chemical formula as $\ce{NH2-C5H10-COOH}$. On the wikipedia page, https://en.wikipedia.org/wiki/Leucine, there are two dissociation constants, one for ...
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1answer
114 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
343 views

How would one correct for a blank in a potentiometric titration?

I want to do a potentiometric titration with perchloric acid of a sample consisting of active drug (weak base) and two other components. Based on theory, I already know that these two other components ...
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2answers
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Can hydrofluoric acid etch glass at a pH of 7.0?

Will it still etch glass when very dilute? Will the reaction still proceed slowly? At what pH will the reaction stop completely? From Wikipedia on hydrogen fluoride: "Although hydrofluoric acid is ...
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9k views

Diluting acetic acid to obtain a solution of pH 5 [closed]

What percent of a solution needs to be acetic acid for a particular $\mathrm{pH}$? I have 100% acetic acid, and want $1~\mathrm{L}$ of solution with a $\mathrm{pH}$ of 5. I've done some research, but ...
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1answer
127 views

Impossible pH For Aqueous Weak Acid Solution

An aqueous solution of $\ce{HCl}$ has a $\mathrm{pH}$ of $0.00$ if $[\ce{H+}] = 1.00 \; \mathrm{M}$. I tried to see if an aqueous solution of acetic acid could have a $\mathrm{pH}$ of $0.00$, given ...
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Carbonic acid-hydrogencarbonate buffer system pH calculation?

I am learning about the pH of buffer solutions, and am slightly confused by my text book's calculation. For the blood's buffer system of carbonic acid and hydrogencarbonate ions as the conjugate case, ...
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2answers
617 views

How to report pH values?

I have measured the pH in the water-soluble fraction of a powder. I weighed in a certain amount of powder and a certain amount of water, and extracted the water-soluble fraction. I then measured the ...
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1answer
715 views

How do I know that an acid and conjugate base are present in equimolar amounts?

Acetylsalicylic acid is a molecule in several popular drugs such as Magnyl and aspirin. Its pKa is 3.5, and I'm about to calculate the pH of a 0.010 M solution of acetylsalicylic acid. I've read up ...
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1answer
153 views

Carbonate + acid reactions - How to recognize these type of reactions?

So I've got $$\ce{CaCO_3 + HCl \rightarrow CO_2 + H_2 O + CaCl_2}$$ I'm wondering how I can recognize these types of reactions? I know that when I mix an acid and a base I get salt and water but in ...
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Why does the pH of this solution rise instead of fall when exposed to the atmosphere?

I have a couple of big barrels with a $50\,\mathrm{L}$ demi-water solution of the following nutrients: $$ \begin{array}{rl} 200~\mathrm{\mu M} & \ce{NH4NO3} & +\\ 30~\mathrm{\mu M} & \ce{...
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1answer
336 views

Amphoteric amino acid titration

Glycine $(\ce{NH2CH2COOH})$ is an amino acid with two $\mathrm{p}K_a$ values $(\mathrm{p}K_{a,1}=2.0, \ \ce{COOH};\ \mathrm{p}K_{a,2}=10.0, \ \ce{NH2})$. (a) If $0.01~\mathrm{mol}$ of this amino ...
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1answer
122 views

Less maintenance-dependent continuous pH testing

I am creating an automated chemical component mixing system (DIY project). One of the features required is continuous monitoring of pH value in my main solution. I do not need it to be very precise, ...
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1answer
2k views

What's the difference between isoionic point and isoelectric point?

What's the difference between isoionic point and isoelectric point? My teacher uses them interchangeably, but Wikipedia states that isoionic point is when charges are balanced, while isoelectric point ...
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1answer
111 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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1answer
1k 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 ...
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Acid disassociation constant of an acid when pH of a solution is given

Q. A solution contains $\pu{0.09M}~\ce{HCl}, \pu{0.09M}~\ce{CHCl2COOH}$ and $\pu{0.1M}~\ce{CH3COOH}$. The pH of the solution is 1. If $\ce{K_a}$ for acetic acid is $10^{-5}$, then calculate $\ce{K_a}$ ...
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1answer
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Can the colour change in litmus paper be explained by conjugated systems?

I have been trying to understand the colour change in litmus paper on a more detailed level than "the chemical identity changes, and therefore also physical properties". I have knowledge of the ...
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1answer
140 views

Is there any reason to fear personal exposure to rain with a pH of 3.1?

Where I live now there can be significantly acidic rain. The government posts measurements for many cities and there can be stretches for days or longer with reported pH of 3.2 or 3.1. I even saw 2.9 ...
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Solubility Product and Buffers

I've been assigned a homework and the question looks like this :- The ionization constant of benzoic acid is $6.46 \times 10^{-5}$ and solubility product for silver benzoate is $2.5 \times 10^{-13}$...
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1answer
661 views

Accuracy of pH meters in MgSO4 solution

I bought a 2 pH meters several months back from Amazon for roughly $10 a piece. I couldn't tell you how they work, but here's the link on Amazon: http://www.amazon.com/gp/product/B0087LOWIA/ref=...
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1answer
847 views

What is the pH of this H2SO4 solution? [duplicate]

I'm trying to solve a simple problem which is driving me crazy. It says: Estimate the pH of a solution that contains 1 gram of $\ce{H_2SO_4}$ dissolved in 1 liter of water. When I solve the ...
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1answer
899 views

Calculating the pH of a ammonium hydrogen sulfate solution

I am attempting to complete a question in which I need to use an ICE table to calculate the pH of a $\pu{2.61 mol L-1}$ $\ce{NH4HSO4}$ (ammonium hydrogen sulfate) solution. When $\ce{NH4HSO4}$ ...
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1answer
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Effect of pH on positive and negative charges of a zwitterion

I read that the isoionic point is defined as the pH at which a zwitterion molecule has an equal number of positive and negative charges and no adherent ionic species. I have two questions ...
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1answer
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Identifying unknown solution with indicators. why is one pKa value ignored and how to treat negatives values?

Three test tubes contain an identical solution of unknown pH. The first one is tested with thymolphthalein and turns colourless The second is tested with a-naphtholphthalein and turns blue ...
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1answer
844 views

Calculating charge of amino acids (am I doing it right?)

Please consider this picture of a peptide chain: I've done some examining on the different amino acids and concluded that the chain is as follows: Lys-Leu-Gly-Ser-Citrullin (variant of arginine). I ...
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1answer
687 views

Red Cabbage Indicator colour change with Sodium Metabisulphite

I made some pH indicator by boiling and straining cabbage juice and in an effort to keep it from spoiling for a while without having to store it at fridge temperatures I added some wine making ...
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1answer
135 views

Isoelectric pH of colloids?

How did we derive the relation between the isoelectric pH and the dissociation constants for the amino and carboxyl groups on zwitterionic amino acids. $$pI=\frac {pK_{a1}+pK_{a2}}{2}$$ where $$\ce{...
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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 ...