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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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77 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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2answers
40 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
27 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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1answer
187 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 ...
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0answers
14 views

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
20 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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0answers
13 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 ...
2
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1answer
45 views

Formation of silica from TEOS

Usually tetraethyl orthosilicate/tetraethoxy silane (TEOS) is mixed with both ethanol and water to produce silica in a sol-gel process. I am curious what happens if one adds TEOS to water at a high pH,...
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1answer
31 views

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
273 views

In the graph provided, which of the substances is the most efficient in acting as an antacid?

If every dot represents the addition of 0.1 g of the respective base. I suppose that the best would be the one that reaches the highest pH, in the shortest time, for example Calcium Carbonate, but if ...
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1answer
41 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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1answer
171 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
38 views

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
33 views

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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1answer
28 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
47 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 ...
3
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1answer
90 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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1answer
39 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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2answers
38 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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0answers
15 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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3answers
1k views

Buffer Capacity Calculation

I know buffer capacity is the following: $$β=\frac{Δ(\ce{H+})}{Δ(\mathrm{pH})}$$ specifically the amount of acid/base that needs to be added to change pH by 1 unit. If I have data about how pH of a ...
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Calculating Buffer Capacity

I completed a titration of Ammonium Acetate buffer solution and to it I added $\pu{2M}$ Hydrochloric Acid. I measured the initial $\ce{pH}$ of the buffer solution before any acid was added and I ...
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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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0answers
12 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: where Cbuf is the total concentration of buffer and Kw is the water ionization ...
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1answer
38 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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2answers
64 views

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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2answers
363 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 ...
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1answer
34 views

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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3answers
345 views

How to make a pH 6.8 Tris buffer?

To preface this, I am a biologist. I need to make a $\mathrm{pH}=6.8$, $\pu{1 M}$ Tris buffer. We have access to Tris base and Tris Hydrochloride. (Unfortunately, none of the fancy Tris compounds ...
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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
503 views

Applying Henderson–Hasselbalch equation to amino acids: which pKa to use to calculate Z-/HZ ratio?

I was wondering which $\mathrm{p}K_\mathrm{a}$ to use when calculating the ratio of $\ce{HZ}$ to $\ce{Z-}$ of amino acids, the Henderson–Hasselbalch formula used: $$\mathrm{pH} = \mathrm{p}K_\text{a} ...
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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
52 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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2answers
1k views

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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474 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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1answer
64 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{[...
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1answer
107 views

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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116 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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1answer
40 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
47 views

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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1answer
2k views

How to calculate pH of solution made of H3PO4 and Na3PO4? [closed]

I am unable to calculate the $\mathrm{pH}$ of a solution made of $\pu{0.1 M}$ $\ce{H3PO4}$ and $\pu{0.05 M}$ $\ce{Na3PO4}$. How to set the approximation and which ions are present at the ...
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0answers
28 views

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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0answers
31 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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2answers
23k 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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2answers
73 views

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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2answers
62 views

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
87 views

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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3answers
8k views

How do indicators work when they mixed with each other?

Methyl orange, bromothymol blue and phenolphthalein indicators were mixed together to form a solution. Over what pH range would the solution be yellow? I cannot understand the question. If two or ...
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3answers
462 views

The effect of NaCl on the ability of an acid to protonate benzoate

I've been doing several experiments using soda to quantify the amounts of caffeine and benzoate. Because of our methods of analysis, we had to decarbonate our soda. The experiment offered two ways for ...