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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4
votes
3answers
125 views

Iterative method for calculating pH of a weak acid / base

The problem asks to determine the $[\ce{H+}]$ in a $0.20~\mathrm{M}$ solution of $\ce{Na3PO4}$. The $K_\mathrm{a}$ of $\ce{HPO4-}$ was given as $4.5\times 10^{-13}$, which then allows one to calculate ...
16
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2answers
2k views

pH probe bulb - what is happening within the glass?

I am trying to understand how the glass bulb of a pH electrode of a pH meter works - the glass bulb itself. Not the reference electrode or the rest of the electrode (HCl, Ag/AgCl wire, etc...), the ...
-2
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0answers
21 views

How do you calculate pH, with different types of acids in solution? [on hold]

New question 41.0 mL of 0.0150 M hydrochloric acid, 130 mL of 0.0650 M hydroiodic acid and 55 mL of 0.00680 M sulfuric acid are pipetted into a 250 mL volumetric flask, which is then filled up to the ...
-2
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0answers
15 views

In the picture below, which one is acidic, alkalalinse and neutral [on hold]

Which form do you think is present at acidic pH, which one in neutral solutions, and which one in alkaline solutions? Briefly justify your answers, based on the availability of protons at different pH ...
-2
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0answers
20 views

How to calculate pH of final solution using volume and pH of initial solutions? [on hold]

When two solutions of equal volume with pH 2 and 8 are mixed, what happens to resulting pH ? How to calculate the final pH? I am being too specific this time.
4
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1answer
2k views

How does pH affect the degradation of ascorbic acid (vitamin C)?

I know that vitamin C degrades over time (as I understand through oxidation). However, I am having trouble understanding how changing the pH of the solution in which the vitamin C is affects the rate ...
1
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0answers
42 views

Calculating ionic strength and pH of a buffer solution [on hold]

Im trying to calculate ion strength and pH of solution. Components of the solution: 47 ul of 1000 pmol DNA in Elution Buffer (10 mM Tris-HCl pH 8.5) was bound to 3 ul of 10 µM YoYo1 (flourescent dye) ...
-2
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0answers
29 views

Calculate pH of final solution using volume and pH of initial solutions [closed]

I have an 800mL solution of TBS (pKa=8.06), HCl, and water at a pH of 7.61 to which I add 200mL of pure 7.0 pH water. What is my final pH? Please show me the calculation too.
0
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1answer
2k views

How to calculate pH of the Na2CO3 solution given ambiguous Ka values

This is the exact question I faced on an exam. Calculate the pH of $\pu{0.05 M}\ \ce{Na2CO3}\ (\ce{H2CO3}: K_\mathrm{a,1}= 4\times 10^{-7},\ K_\mathrm{a,2}= 4.7\times 10^{-11})$ Solution $$\ce{...
0
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1answer
309 views

Calculate mass concentration of Ca(OH)2 solution

Can anyone help me calculate the mass concentration of $\ce{Ca(OH)2}$ solution with molar mass $\pu{74.1 g/mol}$ at the $\pu{pH of 12.8}$. My work so far: From the pH I get the molar concentration ...
-2
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1answer
59 views

Why does the addition of tetraethyl ammonium bromide reduce solution pH? [closed]

I am looking at a system that adds tetraethyl ammonium bromide to water. Over time, the concentration of tetraethyl ammonium bromide gradually increases, leading to a fall in the pH. I am trying to ...
98
votes
8answers
55k views

Is a negative pH level physically possible?

A friend of mine was looking over the definition of pH, and wondering if it is possible to have a negative pH level. From the equation below, it certainly seems possible—just have a $1.1$ (or ...
1
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0answers
25 views

Impact of pH? Change in Binding Affinity of protein-ligand complex based on pH and Kd?

When the $\mathrm{pH}$ was $5.0$, the temperature was $\pu{25 °C}$,the $K_\mathrm{D}$ was $\pu{5 μM}$, and [L] was equal to $K_D$, the protein(s) were half bound. Question considers half bound ...
-1
votes
1answer
34 views

How can I prepare two phosphate buffer of different concentrations but give same pH? [closed]

How is it that buffers of different compositions can have the same pH? For example, it is possible to prepare 0.01 M phosphate buffer of pH 7.0 and 0.1 M phosphate buffer of pH 7.0? How? I used ...
1
vote
1answer
41 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 ...
1
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2answers
7k views

Is methyl orange acidic or basic?

It has been saying that if adding too much indicator in solution, the ph value of solution would be changed. From this, it can be saying that indicators have a pH value. Methyl orange is the indicator ...
1
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2answers
46 views

Calculating amount of base needed to achieve a specific pH in a mixed ethanol-water solvent

I'm looking for some way to calculate how much base I will need to add to an unbuffered solvent consisting of a mixture of ethanol and water in order to basify it to a specific reading (10) on an a pH ...
0
votes
1answer
106 views

Understanding the increase in pH of a buffer solution upon incremental additions of NaOH analytically

So let's say we have $200\ \mathrm{mL}$ of $1\ \mathrm M$ $\ce{CH3COOH}$ solution. In this solution we have the equilibrium $\ce{CH3COOH <=> CH3COO- + H+}$. To that we add $100\ \mathrm{mL}$ of $...
1
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1answer
44 views

How a titration curve is affected when a poorly soluble salt is formed?

Suppose that I have $\pu{100 mL}$ solution of strong acid, $\ce{HA}$, at $\pu{0.10 mol L^{-1}}$. This solution is titrated with a strong base solution, $\ce{BOH}$, at $\pu{0.10 mol L^{-1}}$. Suppose ...
2
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0answers
19 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 ...
-2
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2answers
59 views

Finding the pH of the solution

In this video, at 3:30 min professor solves two equations $$\ce{H2O —> H+ + OH-}$$ and $$ \ce{HCl —> H+ + Cl-}$$ and deduces $[\ce{H+}] = [\ce{Cl-}] +[\ce{OH-}]$. How come this happen from ...
0
votes
0answers
19 views

pKa values for amino acid

To calculate the pI value, we take the average of the pKa values from the 2 groups that result in a net charge of 0. For that to happen, the pKa values should be at the midpoint of titration where ...
2
votes
1answer
61 views

What is the formula for theoretical buffer capacity for a diprotic buffer system?

According to Chembuddy, the formula for theoretical buffer capacity for a monoprotic buffer system is as follows: $$β = 2.303\left(\frac{K_\mathrm{w}}{[\ce{H+}]} + [\ce{H+}] + \frac{C_\mathrm{buf}...
1
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1answer
26 views

The time-dependent pH value in a fermentation

I want to know if someone has supporting tips or solutions to my problem: In biotechnology, fermentations are used to grow microorganisms. These need a specific media/broth in which temperature, pH, ...
-1
votes
1answer
38 views

How to predict whether a salt will act as an acid or as a base in aqueous medium? [closed]

How to would we know if a salt such as $\ce{CO_2}$ reacts acidic or basic in water. The explanation I see everywhere is that you have to see the acid and base that makes up the salt, in the case of $\...
-3
votes
1answer
53 views

How does sodium carbonate reduce pH?

Sodium carbonate is used in pools to raise pH. From my understanding, it would dissociate in water like so: $$\ce{Na2CO3 <=> 2 Na+ + CO3^2-}$$ To raise pH, doesn't it have to absorb hydrogen ...
1
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1answer
101 views

pH of very dilute acids

From doing some research on the site I have found that many people have posted about solutions of $\ce{HCl}$ where $[\ce{HCl}] = \pu{1e-8 mol dm-3}$ Here they are able to deduce $$[\ce{H+}] = \frac{[...
1
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1answer
42 views

Acid solution — lower pH when diluted

Today I came across a "thought experiment" regarding $\mathrm{pH}$ of a diluted acid solution. This idea looks somewhat logical but obviously contradicts the reality. Can you show me where is the ...
3
votes
0answers
31 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 ...
0
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0answers
44 views

What is the pH of a solution of iron acetate?

What is the pH of a $\ce{0.1 M}$ solution of $\ce{Fe(CH_3COO)_3}$? I'm not sure how to do this, as it would involve complicated mass balance equations, but I think I can apply the approximation $\ce{...
0
votes
3answers
65 views

Doubt on process to calculate pKa [closed]

I have to solve an exercise that I've been trying for a long time without success. Information that I have: pH @ certain temperature of an aqueous dissolution of an acid molar concentration ...
2
votes
1answer
53 views

Confusion regarding calculating the pH of a salt of weak acid and weak base

I need to calculate the $\mathrm{pH}$ of a salt of weak acid and weak base in an aqueous solution. Method I used for calculation For a salt of weak acid and weak base (assuming complete dissociation ...
-1
votes
1answer
2k views

Calculating the pH upon titrating barium hydroxide and hydrochloric acid

Question: Calculate the pH produced from mixing $\pu{25.0 mL}$ of $\pu{0.420 M} $ $\ce{Ba(OH)_2}$ with $\pu{125 mL}$ of $\pu{0.120 M}$ $\ce{ HCl}$. Attempt: I'm learning about acids and bases ...
1
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1answer
64 views

Titration of barium(II) hydroxide by hydrochloric acid

$\pu{25 ml}$ of $\pu{0.024 M}$ $\ce{HCl}$ is titrated into a volumetric flask which initially contains $\pu{45 ml}$ of $\pu{0.034 M}$ $\ce{Ba(OH)2}$. Calculate the $\mathrm{pH}$. This is how I ...
1
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1answer
55 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 ...
1
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0answers
18 views

Why might litmus paper and universal indicator give conflicting pH readings in an acid-carbonate reaction?

The resulting neutralised (which wasn't actually neutralised due to not realising CaCO3's insolubility) solution between Hydrochloric Acid and Calcium Carbonate, as per balanced equation CaCO₃ + 2HCl ...
-3
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1answer
30 views

Acid/Base Indicator [closed]

I'm not sure how the concept and math work on this problem. Can someone show me how you can get the answer, both conceptually and using math?
-2
votes
1answer
26 views

Calculating the pH of Strong Acid Solutions [closed]

Calculate the $\mathrm{pH}$ of a $\pu{1.5e–11 M}$ solution of $\ce{HCl}.$ How is the $\mathrm{pH}~7?$
7
votes
1answer
162 views

Amending soil pH to change the color of hydrangea flowers

I would like to ensure that my hydrangeas are blue. I am told that adding ammonium sulfate or aluminium sulfate will cause the soil to be more acidic. I am also told that adding elemental sulfur will ...
2
votes
1answer
211 views

Why does slaked lime water lose alkalinity over time?

When I throw 3 handfuls of white lime $\ce{Ca(OH)_2}$ into 60 gallons of tap water, the initial pH value is 11.4, but unknowingly it changes to pH 7. What is the chemistry behind it? How long does ...
2
votes
1answer
72 views

Why does pH of a buffer solution change according to Henderson–Hasselbalch equation? [closed]

If I add a little amount of acid or base to a buffer solution, the pH of the buffer won't change. That's what the diagramatic mechanism tells us. But according to Henderson–Hasselbalch equation, the $...
1
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0answers
28 views

Do TDS meters measure HCO₃⁻/CO₃²⁻?

I am trying to add $\pu{2 g}$ of $\ce{KHCO3}$ to $\pu{20 L}$ of RO water $(\mathrm{pH} = 5.2)$ which theoretically it will add $$ \begin{array}{lr} \hline \ce{K+} &\pu{10.32 ppm} \\ \ce{HCO3-} &...
0
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0answers
20 views

What is the cause for the difference in pH between NaCl and Ringer Lactate

Reading this article, I came across a passage which got me to think of this question: "Normal saline contains approximately $\pu{154mM}$ of each $\ce{Na+}$ and $\ce{Cl-}$ with average pH of 5.0 and ...
1
vote
0answers
28 views

Acid and base separation on an anion exchange column [closed]

I'm new with this concept and so I would need some advice. I want to separate an acid and a base in a water solution. The acid has $\mathrm{p}K_\mathrm{a}(\ce{HA}) = 5$ and the corresponding acid of ...
9
votes
1answer
4k views

Is there a means to measure pH without indicators?

I have created a solution that should contain hydroxide ions. Therefore, the pH > 7, but is there any way to roughly estimate the pH in absence of any indicator? Maybe using current, or checking ...
0
votes
0answers
55 views

Calculate the pH

Calculate the pH of a dissolution of 100 ml of 0.1 M solution of ammonium chloride in the style of 100 ml of 0.1 M hydrochloric acid solution $\ce{NH4Cl -> NH4+ + Cl-}$ $\ce{HCl -> H+ + Cl-}$ ...
12
votes
2answers
818 views

Why are synthetic pH indicators used over natural indicators?

Synthetic indicators seem to be exclusively used when determining the pH of a substance with an indicator (with the exception of that school experiment where you boil cabbage to demonstrate natural pH ...
2
votes
0answers
51 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 ...
1
vote
1answer
108 views

Calculating pH when weak base is added to an strong acid

$\ce{NH3}$ solution of $\pu{0.1 mol dm-3}$ is being added to a $\pu{25.0 cm3}$ of $\pu{0.1 mol dm-3}$ $\ce{HCl}$ solution. Calculate the pH of the solution when volume of added $\ce{NH3}$ solution is $...
1
vote
1answer
124 views

Why do weak acids like ethanol not act as a strong base in water?

In water, ethanol has a $\mathrm{p}K_\mathrm{a} = 15.9$ which means that its $\mathrm{p}K_\mathrm{b}$ is $-1.9$. Which implies that all weak acids in water are in fact strong bases. But this is not ...