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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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Why does the pH of a reaction between magnesium and hydrochloric acid stay the same?

I did an experiment where I reacted magnesium with hydrochloric acid and tested the pH of the solution at the beginning and at the end. My pH paper told me that the pH did not change or at least very ...
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1answer
14 views

pH calculation and concentrations of all species present in a solution [on hold]

When $\ce{NO2}$ is bubbled into water, it is completely converted to $\ce{HNO3}$ and $\ce{HNO2}$: $$\ce{NO2 + H2O -> HNO3 + HNO2}.$$ Calculate the $\mathrm{pH}$ and the concentrations of ...
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How much Sodium Bicarbonate (NaHCO3) do I need to add to specific volume of water to increase the pH by specific amount? [on hold]

I'm trying to increase the pH of a nutrient solution for algae I'm attempting to grow. I suspect that my algae will grow at a higher pH than contaminants. I want to raise the pH of a container of ...
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1answer
27 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 $\ce {[HCl]=10^{-8} mol dm^{-3}}$ Here they are able to deduce $$\ce{[H^+] =\frac{[...
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2answers
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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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Why do some cations and anions interact with water to form corrresponding acids and bases(hydrolysis)? [duplicate]

I have seen in my textbook that on cations/anions formed on ionization of salts either exist as hydrated salts in aqueous solutions or interact with water to reform corresponding acids/bases depending ...
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1answer
482 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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4 views

What is the optimal pH for electrolysis? [closed]

I am Electro etching some metal and I'm trying to find the optimal pH / optimal DIY mixture for a cost-effective electrolyte.
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1answer
31 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
332 views

What is the pKa of iodous acid?

Searching the web readily gives the $\mathrm{p}K_\mathrm{a}$ of hydroiodic acid, hypoiodous acid, and iodic acid, however, extensive searching did not result in any value of the $\mathrm{p}K_\mathrm{a}...
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1answer
28 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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3k views

Determining the pH of an organic solvent

Our work is faced with the issue of determining the charge of compounds that are dissolved in chloroform. One could realistically determine the charge of the relevant moieties knowing the $\mathrm{p}...
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1answer
25 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
47 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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2answers
33k views

Volume required to dilute solution for a pH change

A $\pu{100 mL}$ solution of $\ce{NaOH}$ has a $\mathrm{pH}$ of $13$. What volume of water in $\pu{mL}$ must be added to change the $\mathrm{pH}$ to $11$? My steps: Begin by calculating conc. of $[\...
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2answers
834 views

Why does adding salt to water reduce the pH?

I recently heard someone claim that adding table salt to vinegar caused HCl to form which helped them clean coins - clearly not the case - however I thought I'd disprove it by doing an experiment. So ...
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2answers
8k views

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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35 views

Calculating pH of extremely dilute HCl solution [duplicate]

The $pH$ of a $10^{-8} M$ (M = moles per liter) $HCl$ solution is to be calculated. The plan is to calculate the ionization constant ($K_a$/acidity) first, and then derive the $pH$. However, as the ...
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4answers
520 views

Why can't the strength of superacids be measured in water?

I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to ...
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2answers
5k views

Effect of pH on electrolysis

I understand(more or less) that acidification of water helps in the dissociation of water into ions. Acids easily dissociate into ions in aqueous solution. So accordingly the hydrogen from the acid ...
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1answer
22 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 ...
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12k views

Does the number of H+ ions in solution go up on dilution of a weak acid?

In my textbook, a footnote says: In case of weak acids, on dilution the total number of $\ce{H^{+}}$ ions in solution increases because dissociation of the weak acid increases This didn't make ...
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1answer
118 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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3answers
5k views

Sugar solutions have a neutral pH in themselves, but it makes your body acidic. Why? [closed]

I'm not an expert, but as far as I understood a sugar solution is completely neutral since sugar can't take hydrogen ions out of the water or donate them in. Sugar is a non ionic compound, so it does ...
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1answer
817 views

pH of a buffer solution calculation

Calculate the pH of a mixture of $75\:\mathrm{cm^3}$ of methanoic acid solution of concentration $0.10\:\mathrm{mol\:dm^{-3}}$ and $75\:\mathrm{cm^3}$ of sodium hydroxide solution of concentration $0....
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1answer
2k views

Dissolving Tylenol Science Experiment - why is it fastest in distilled water?

My son has a science experiment for class to dissolve Tylenol (325mg acetaminophen) in 3 different solutions (125 mL volume each): Distilled water Vinegar (1 part white vinegar to 4 parts water) Salt ...
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2answers
3k views

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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15k views

If you add AlCl3 to water, why does the pH decrease?

You are not adding any hydrogen ions, so why does the pH of the solution decrease? Thank you in advance. EDIT: I will add the context of my asking this question to clarify some details. This is not ...
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1answer
138 views

How to solve for concentration of two equilibrium reactions with finite equilibrium constants?

I have a small problem of equilibrium that I counldn't solve. I want the exact answer. No approximations please. $$ \begin{array}{ll} \ce{H2O + H2O <=> H3O+ + OH-} &\quad\left(K_w = 1\cdot ...
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1answer
123 views

Optimum pH range for formation of Schiff bases

What is the optimum range of pH for the formation of Schiff Bases by the addition of hydroxylamine to an aldehyde or a ketone? According to Peter Sykes' A Guidebook to Mechanisms in Organic Chemistry,...
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1answer
27 views

Regarding acid-base reactions, how does one know when a hydrophobic base substance is fully protonated?

When there's a weak base substance (hydrophobic powder), and it needs to be completely protonated by adding an acid (eg: HCl), how does one know when it's completely protonated? Since the powdered ...
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1k views

Why does saline have a pH of 5.5?

I am a physician and administer 0.9% NaCl in water ("normal saline") to patients frequently. The bag says it has a pH of 5.5 (compared to the human body of 7.4). I am asking why the pH is so low. It ...
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2answers
1k 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 ...
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35 views

Seeming discrepancy between pKa and corresponding Ka of methylamine

The first entry in PubChem for the $\mathrm pK_\mathrm a$ of methylamine is $10.657$ at $25\ \mathrm{^\circ C}$. My elementary understanding is that this would be found as the negative log of the $K_\...
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2k views

Why should colorimetric titration of a weak acid with a weak base not be done in laboratory? [closed]

Why should colorimetric titration of weak acid with a weak base (or vice versa) not be done in laboratory? How can I draw a pH graph for this?
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3answers
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What is the necessary volume of concentrated HCl to prepare a solution with a pH of 1.8?

I am trying to solve the following exercise: What volume of a concentrated $\ce{HCl}$ solution, which is $36.0\%$ $\ce{HCl}$ by mass and has a density of $1.179~\mathrm{g~mL^{-1}}$, should be ...
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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 ...
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2answers
9k views

Why does an acid have a low pH value?

When study biology in class, I don't know how my teacher get to the topics on pH value. So, she says that pH stands for percentage hydrogen. Then, I thought there is something strange about it cause ...
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37k views

The reason behind the steep rise in pH in the acid base titration curve

Most books refer to a steep rise in pH when a titration reaches the equivalence point. However, I do not understand why … I mean I am adding the same drops of acid to the alkali but just as I near the ...
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41 views

Understanding how the definitions of pH and activity are compatible

At $T=\pu{25 ^\circ C}$ and $P=\pu{1bar}$, the density of water is $\pu{0.997 kg L-1}$. Neglecting nonideality of the mixture $\ce{H2O(l), H+}$ and $\ce{OH-}$ (all activity coefficients are close to $...
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2answers
16k views

MgCl2 acidic or neutral in water?

I'm currently taking chemistry 12. On our test we were asked, when given a $0.1~\mathrm{M}$ solution of certain compounds whether the resulting solution when added to water would be acidic, basic, or ...
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1answer
39 views

Experimental determination of pH [closed]

I am trying to determine the experimental pKa for two weak acids that were titrated against 0.20M NaOH. I have read elsewhere that you can take the point where the graph becomes steep and divide the ...
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2answers
69 views

When an acid is added to water, why does the hydroxide ion concentration decrease?

At equilibrium in pure water, we have $$\ce{[H_3O+][OH-]} = 10^{-14}$$ Since $\ce{H3O+}$ and $\ce{OH-}$ ions are produced in pairs, we may conclude $$\ce{[H_3O+]}=\ce{[OH-]} = 10^{-7}$$ So far so ...
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396 views

Should the 'a' in the acid dissociation constant (Ka or pKa) be capitalised?

In science, the negative logarithm of the acid dissociation constant is denoted $\mathrm{p}K_\mathrm{a}$ or $\mathrm{p}K_\mathrm{A}$ depending on the source (lowercase "a" or uppercase "A"). Since it ...
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2answers
3k views

Alkaline glycine buffer molarity

Having never prepared a buffer solution before, I am hoping for a little help in understanding the process. This method I plan to use calls for a $\pu{0.1M}$ glycine buffer at pH $10.6$. Some ...
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1answer
16 views

What are standard controllers for automatic pH control?

My background in control theory comes from electrical engineering (robots, motors, etc.) and I want to build a control system for automatic pH control. Can I directly apply my knowledge from ...
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1answer
39 views

neutralization of a strong acid with a strong base [closed]

When a 1M H2SO4 is mixed with an equal volume of 1M NaOH, is the mixture acidic, basic, or neutral?
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81k views

Why does pH affect fermentation?

I know that the lower the pH the faster fermentation occurs. Why does this happen?
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1answer
37 views

How do I calculate the amount of polyprotic acid and base needed to achieve a certain buffer pH?

e.g. Citric Acid and Trisodium Citrate $\ce{H3C6H5O7 <=>[ka_1] H2C6H5O7- + H+ <=>[ka_2] HC6H5O7^2- + H+ <=>[ka_3] C6H5O7^3- + H+}$ Using the definition of Ka and substituting for ...
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2answers
381 views

Why the pH of xanthan gum in aqueous solution is 7 (neutral) when it has glucuronic and pyruvic acids in its chemical structure?

Since xanthan gum has both glucuronic and pyruvic acids in its chemical structure, it should release $\ce{H+}$ ions upon solvation in an aqueous solution and make it acidic. However, the meausured $\...