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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pH of a Calcium Hydroxide vs Magnesium Hydroxide solution [on hold]
In an AQA 2017 Chemistry paper, a $0.0131 \pu{mol}\cdot\pu{dm^-3}$ saturated solution of calcium hydroxide is prepared and then the question asks to predict the pH of a similar solution of magnesium ...
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2answers
75 views
How to calculate pH of basic salt solution mixed with strong base?
Calculate $\mathrm{ pH }$ of $\pu{ 0.05 mol }$ of $\ce{Zn(CH3COO)2}$ and $\pu{ 0.025 mol }$ of $\ce{ NaOH }$ dissolved in $\pu{ 1 L }$ of distilled water?
I tried to use the systematic method by ...
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1answer
62 views
How do I calculate the hydronium ion concentration if I know the strontium hydroxide concentration?
This is my first question so I would appreciate feedback on how to ask better questions. Forgive me if I don't know how to properly format math/chem. The guide is confusing.
I was taking a practice ...
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2answers
45 views
Calcium Phosphate Dissolution
For what reason does Calcium Phosphate dissolute at low pH? What makes it pH dependent? This question arised after reading about the calcium phosphate bridges in casein micelles and how they 'break ...
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1answer
29 views
By how many pH units does rain vs distilled water change a soil pH test?
Sources state that the concentration of $\ce{H2CO3}$ in rain is of a few µmol; I don't know if that's per ml. The buffering effect of most soils is >1000 µmol $\ce{H+}$/kg.
Is the difference from low ...
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Preparation of Copper (II) Sulfate Pentahydrate Solution
how would you make a solution of Copper (II) Sulfate Pentahydrate to achieve 150, 200, 250 and 300 mgL−1 concentration of copper? I do not have the anhydrous version of the solute. Also, when I ...
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2answers
21 views
Influence of pH on precipitate crystallite sizes?
It's normally assumed that a higher pH of solution would slow nucleation rates and hence lead to larger crystal formation. I've found literature that it is due to solid-liquid inter-facial tension. ...
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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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1answer
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Reference Books on Electrolysis and Chemical Titration process [closed]
I'm in a General Chemistry course in college. We have laboratory, and then we are supposed to make a report on what we did, etc.
I'm not entirely sure what the last laboratory was about, but it was ...
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1answer
42 views
Calculate pH at equivalence point [closed]
Calculate the pH at the equivalence point of a titration of 62 mL of 0.1 M $\ce{CH_3NH_2}$ with 0.20 M HCl. The $\ce{K_b}=4.4\cdot10^{-4}$.
At the equivalence point, the moles of CH3NH2 equals the ...
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Getting pH of a weak acid and conjugate base with a given ratio [closed]
A practice question reads
What is the $\ce{pH}$ of a solution of a weak acid and its conjugate base when the ratio of the concentrations of the conjugate base/weak acid is 1/3? (the weak acid $K_\...
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Can buffer solutions be used to control the pH of ethanol?
For my experiment, I want to investigate the effect of differing pH on the solubilities of a sparingly soluble drug. However, the solubility is too low for me to conduct a reliable study on the ...
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1answer
29 views
Adding weak acid to strong base, find pH [closed]
30mL 3M acetic acid (pka 4.7) is added to 50mL 2M NaOH. what is the resulting pH
a) <2
b) between 2 and 7
c) 7
d) >7
ans =d
can someone explain how to actually solve for pH? the solution ...
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1answer
48 views
Using electrolysis of water as a proton generator [closed]
I'm working on a project right now, where the challenge is to try to use electrolysis as a way of controlling the $\ce{pH}$ of water.
I've set up an experiment where I have two separate chambers or ...
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0answers
16 views
Is it possible to determine the pH that results in maximum buffer capacity from a Bjerrum plot?
If buffer capacity is normally at a maximum when pH=pKa because there is an equal concentration of acid and conjugate base in the buffer (so there's an equal amount of substance that can absorb acid ...
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2answers
41 views
Calculating the pH of a buffer made by a diprotic acid and its double salt
The concentration of the diprotic acid (tartaric acid) will be constant at $\pu{ 0.1 M}$. I want to find the concentration of its double salt (potassium sodium tartrate) needed to create a buffer of $\...
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1answer
25 views
Why does buffer capacity of tartrate buffer generally decrease as the buffer pH increases?
From what I see, the buffer capacity of tartrate buffer is generally decreasing as buffer pH increases. Why is this? Also, does this mean that tartrate buffer doesn't have a maximum buffer capacity at ...
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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:
where Cbuf is the total concentration of buffer and Kw is the water ionization ...
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1answer
42 views
Why is maximum buffer capacity for some diprotic buffers not when pH = pKa?
According to Rajkovic et al. [1]:
$$β = \frac{[\ce{H+}]}{K_\mathrm{w}} + 2.303\cdot\frac{[\ce{H+}]\cdot K_\mathrm{a}\cdot c}{[\ce{H+}] + K_\mathrm{a}}$$
where $K_\mathrm{a}$ is the ...
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1answer
94 views
pH of CH3CH2NH2 buffer solution [closed]
For $\pu{550.0 mL}$ of a buffer solution that is $\pu{0.170 M}$ in $\ce{CH3CH2NH2}$ and $\pu{0.150 M}$ in $\ce{CH3CH2NH3Cl}$, calculate the initial pH and the final pH after adding $\pu{0.020 mol}$ ...
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2answers
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Dissociation degree hell, Ostwald's law of dilution
Greetings dear chemists!
I got a nice exam problem on wich i am stuck for hours, well maybe the problem is with me. I know the problem can be solved. So here we go.
We got a weak monoprotic acid, we ...
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1answer
41 views
Effects of Ka on the Half-Equivalence Point
I'm new to studying chemistry at a university level and am currently reviewing acid-base titrations. I am wondering about the relationship between your ionization constant for a weak acid ($K_\mathrm{...
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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 ...
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Drug pH and pKa known, is it an acid or a base? [closed]
I want to answer the question if a drug which is analysed for pH and pKa is ionised or not ionised in a cow stomach with a pH of 6.
The drug has a pH of 8,52 and a pKa of 8,78.
Since the pH is 8,52 ...
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1answer
21 views
The pH scale/calculating pH level [closed]
How much water do you need to add to 10 mL of a solution of HCl with a pH of 4 to change the pH to 5?
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1answer
38 views
Identifying Lewis acid
What is the Lewis acid on the reactants side?
$$\ce{HNO2(aq) + HPO4^{2-}(aq) <=> NO2-(aq) + H2PO4-(aq)}$$
The book says it is the $\ce{H+}$ only, not the whole molecule of the nitrous acid, ...
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2answers
54 views
not understanding buffering region vs equivalence point [closed]
"During the titration of a weak polyprotic acid with a strong base, the first stoichiometric equivalence point occurs when the moles of added base are equal to the moles of the initial acid species. ...
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1answer
92 views
Determining the reduction potential of a half cell reaction at a given pH
$E^\circ_\ce{Cu^2+|Cu} = \pu{0.34 V}$.
What will be reduction potential at $\mathrm{pH} = 14$ for the same couple?
Given that $K_\mathrm{sp}$ of $\ce{Cu(OH)2}$ is $10^{-19}$.
My Attempt
I think ...
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1answer
41 views
Determination of pKb of a mono acidic base
$20$ mL of a weak monoacidic base($\text{BOH}$) requires $12$ mL of $0.3$ M $\text{HCl}$ solution for the equivalence point. During titration, the pH of the base solution was $10$ upon the addition of ...
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1answer
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Calculate pH of a buffer solution
Calculate the pH in a buffer prepared from $\pu{50 mL, 0.30 M}$ formic acid ($\ce{HCOOH}$) and $\pu{30 mL, 0.40 M}$ sodium formate ($\ce{HCOONa}$).
My way of solving:
$n_{\ce{HCOOH}} = 0.05 \times ...
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0answers
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NMR Prediction for compounds at variable pH values
Like the title says, I'm looking for any software package that may be able to simulate a variety of NMR at a variety of different pHs. The majority of the software programs that I've found do not have ...
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2answers
833 views
Why proton concentration is divided by 10⁻⁷?
I am reviewing the book Biochemistry Concepts and Connections by Appling, Cahill, and Mathews and I cannot understand why they divide by the hydrogen concentration by $10^{-7}$. Why not just leave it ...
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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 ...
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2answers
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Should the tip of the burette of an automatic titrator be immersed in the analyte?
In all the tutorials I found online, the tip of the burette (containing the titrant - NaOH) was immersed into the analyte solution. My question is: shouldn't the tip be out of the solution? Isn't ...
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What are the concentration changes when diluting an equimolar acetic acid: acetate buffer?
When a buffer (for example, a mixture of 100 mM acetic acid and 100 mM acetate), is diluted 10-fold, all the concentrations change drastically. Surprisingly, after re-establishment of equilibrium, the ...
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1answer
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How is preparing a buffer possible?
I understand the concept of an equilibrium buffer solution, however I am a bit hung on how creating it doesn't shift the weak acid equilibrium.
$$\ce{CH3COOH + H2O <=> CH3COO- + H3O+}$$
$$ K_\...
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1answer
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What alkali and alkaline earth metal oxides will turn moist red litmus blue and finally white? [closed]
How many of the following will turn moist red litmus blue and finally white?
$\ce{Li2O}$, $\ce{KO3}$, $\ce{RbO2}$, $\ce{Cs2O2}$, $\ce{BeO}$, $\ce{MgO}$, $\ce{BaO2}$, $\ce{SrO}$.
Since bleach ...
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54 views
What is the benefit of using a pH indicator reagent over pH strips or a meter?
I've recently started getting into chemistry a bit as a hobby. Nothing serious, just amateur level stuff mostly, primarily just to educate myself.
Whenever I need to determine the pH level of a ...
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1answer
46 views
Dissociation behaviour of polyelectrolytes
Assuming a solution of 100 polycationic molecules, each of them carrying 100 amino groups and an apparent pKa of 6.5. Would it mean that, at a pH of 6.5,
50 molecules will be fully protonated
50 ...
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2answers
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What's wrong in this?
While calculating pH of 10^-8M HCl, we take into account the H+ ions released by water. But water also releases OH-ions.So she shouldn't they neutralise the H+ ions?
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2answers
115 views
Can an acid have a high pH? [closed]
I am studying anesthetics and came across thiopental which is considered a weak acid. However it has a pH of 10.5. I always learned that greater than 7 is alkaline. I’m looking for some guru to help ...
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1answer
46 views
Concentration of Hydrogen Ions
I am slightly confused about one certain task.
There are 4 different solutions ($\ce{NH3}$, $\ce{HCl}$, $\ce{NaOH}$, $\ce{CH3COOH}$), their concentration is the same $(c = \pu{1 mol L-1}).$ Which ...
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3answers
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Solubility and pH
I was reading about antacids. It stated that in earlier times $\ce{NaHCO3}$ and a mixture of aluminium and magnesium hydroxide were used as antacids. In excess $\ce{NaHCO3}$ can make the medium ...
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1answer
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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{[...
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2answers
95 views
Calculating dissociation degree from pH and Ka without given initial acid concentration
Is it possible to calculate the dissociation degree (DD) from pH and Ka without directly been given the initial acid concentration?
I found the following formula:
$$\text{DD} = \frac{K_\mathrm{a}}{...
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1answer
38 views
How to calculate the pH of a solution given the concentration and pKa's of solutes? [closed]
For example, if I have a solution of 50mM acetlycholine (pKa = 4.5), how would I go about calculating the pH of the solution?
Thanks
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1answer
34 views
pH change with temperature
I understand that the pH of solutions decreases as the temperature increases but is there a reason as to why some solution's pH decreases more than others even if the temperature change is the same?
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1answer
37 views
Evaluate mass of salt needed to add to a buffer solution knowing only pH
This is an exercise taken from an old exam, I'm struggling with the resolution.
To a solution of a generic weak acid $\ce{HA}$ were added $\pu{2.40 g}$ of a potassium salt of the $\ce{KA}$. The ...
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1answer
53 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
35 views
Why must a buffer solution contain both a weak acid and a salt solution of its conjugate base?
Doesn’t the weak acid dissociate to produce the conjugate base on its own?
I understand that when a strong base is added to the buffer solution, the hydroxide ions will react with the hydrogen ions ...
