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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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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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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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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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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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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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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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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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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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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577 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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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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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
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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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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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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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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 $\...
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How to find pH by mixing two solutions of different concentrations?

A mixture is made by combining 110 mL of 0.15 M $\ce{HCl}$ and 215 mL of 0.055 M $\ce{HI}$. What is the pH of the solution? $$\ce{HCl -> H+ + Cl-}$$ $$\ce{HI -> H+ + I-}$$ According to what I ...
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Wood Hydrolysis

According to this article on Live Strong, children have an average saliva pH of 7.5, while adults tend to be more acidic, with a saliva pH of 6.5 or lower. Even though a pH of 6 is not very ...
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Does a solution of pH zero contain hydroxide ions? [closed]

Are there hydroxide ions in a solution of pH 0?
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Where on the backbone does a peptide get protonated at low pH?

As a particular example, how does the backbone of a peptide look at $\mathrm{pH}~2$? Where does the backbone get protonated in such an acidic solution? I know that at low $\mathrm{pH}$ the free ...
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Which salt will best be able to buffer the addition of HCl?

From these three salts, which will be best able to buffer the addition of $\ce{HCl}$? ammonium chloride sodium carbonate ammonium acetate. I think sodium carbonate is the right choice ...
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1answer
282 views

Why doesn't pH = pKa1 in the buffer zone for this titration?

Below is an image from my textbook representing the titration curve for the titration of $5.00\ \mathrm{mL}$ of $0.010\ \mathrm M$ $\ce{H2S2O3}$ with $0.010\ \mathrm M$ $\ce{KOH}$, which has $\mathrm ...
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pH throughout a titration

Estimate the $\ce{pH}$ of the solution that results when $\ce{75.0 mL}$ of $\ce{0.275 M HCl}$ is added to $\ce{50.0 mL}$ of $\ce{0.275 M Na2HPO4 (aq)}$. My book gives the successive $\ce{Ka}$ values ...
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1answer
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Acid neutralization [closed]

I am working on a biogas plant, digester volume 3000 liter, right now pH condition is acidic at 4.00 my requirement is to maintain pH to 6.50 to 7.20 what should I do? some suggestions are there like, ...
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How do I find the theoretical pH of a buffer solution after HCl and NaOH were added, separately?

This question is about the theoretical pH of a buffer solution. Calculate the theoretical pH values expected for a $\pu{200mL}$ buffer solution containing a 1:1 ratio of acetic acid and sodium ...
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Water values and water hardness

We have drinking water with the following values: Calcium mg/l 62.7 Magnesium mg/l 10.3 total hardness 7.) dH 11.1 Total hardness 7) mmol/l CaCO3 1,99 Carbonate hardness °dH 8.5 ...
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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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What are the products of the dissociation of sodium bicarbonate in water? What is the relative pH of the solution?

I had a recent question on a test that asked what the products would be if sodium hydrogen carbonate were dissolved in water. I had a few candidate answers $\displaystyle\ce{NaHCO3 -> Na+ + HCO3-}$...
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Calculating the pH of a highly dilute solution of HCl

For relatively high concentrations of $\ce{HCl}$, I usually just assume that $[\ce{H+}] = [\ce{HCl}]$, because $\ce{HCl}$ is a strong acid and is completely ionized in solution. By taking the negative ...
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What is the pH of CsBr?

What is the pH of CsBr? 3.8 7 9 12 According to me, $\ce{Cs+ + H2O <<=> CsOH + H+}$ (because $\ce{CsOH}$ is a strong base, the forward reaction should not occur, right?) ...
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EQPt pH of a Monoprotic Acid-Base Titration: Product of Molarites Over Their Sum

Context The Henderson-Hasselbalch equation is as follows. $$pH=-\log\big(K_a\big)+\log\bigg(\frac{[A^-]}{[HA]}\bigg)$$ One may follow its derivation in order to understand how it came to be, yet ...
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756 views

Calculate pH of a weak acid and weak base neutralization reaction

I'm an industrial pharmacist needing some help with some chemistry basics. I'm trying to calculate the theoretical pH of an effervescent preparation containing 2 mmol citric acid ($\ce{H3C6H5O7}$), 4 ...
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What chemicals are in tap water that gives it a slightly basic pH level

In chemistry, we recently did a lab where we observed the different ways of reading pH of several different substances. We used things such as red cabbage juice, litmus paper, pH paper and a pH probe. ...
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1answer
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Confusion About Acid/Bases That Don’t Follow the Arrhenius Definition [closed]

I understand that acidity is merely a reflection of how many free hydrogen ions are in water, and basisicity is just a reflection of the number of hydroxide ions, but I don’t understand how this ...
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1answer
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Does dilution of a buffer affect pH?

The Henderson-Hasselbalch equation for the $\mathrm{pH}$ of a buffer solution of the monoprotic acid $\ce{HA}$ is given by $$\mathrm{pH}=\mathrm pK_\mathrm a+\log{\frac{[\ce{A-}]}{[\ce{HA}]}}$$ Since ...
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Why is a buffer solution best when pH = pKa i.e. when A-/HA=1

Buffers work best when $\mathrm{pH}$=$\mathrm{p}K_\mathrm{a}$ From the Henderson-Hasselbalch equation, $\mathrm{pH}= \mathrm{p}K_\mathrm{a} + \log_{10}\left(\frac{[\ce{A-}]}{[\ce{HA}]}\right)$ If $...
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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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Calculating the pH of a weak acid from the Kb of its conjugate base

I'd start off by saying it's been many years since I was in chemistry lessons and have forgotten much, but recently I have had to relearn a lot of basic chemistry. The following doesn't really impede ...
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171 views

Safely lowering bleach pH without chlorine gas?

According to Eurekalert, by lowering the pH of household bleach (e.g., by adding vinegar or citric acid), we can increase $\text{[HOCl]}$ and consequently greatly improve the disinfecting capabilites ...
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The effect of pH and solubility on coagulation in water treatment

In water treatment, a specific pH range must be met in order for the process of coagulation to occur properly. Sources have stated this is due to the pH affecting the solubility of the coagulant, but ...
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Working out pH of solution when excess NaOH is added

In a pH titration, $30\text{cm}^3$ of $\ce{NaOH}$ is added to $\pu{20 cm3}$ $\ce{CH3COOH}$. The concentrations of both solutions was $\pu{0.5 mol dm-3}$. $K_\mathrm{a} = \pu{1.7 x 10^{-5}}$ for $\ce{...
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Finding the pH value of HF [closed]

Find the pH value of HF. $pH = -\log[H+]$ for strong acids $pOH = -\log[OH-]$ for strong bases $pH = 1/2(pKa - \log C)$ for weak acid $pOH = 1/2(pKb - \log C)$ for weak base HF is weak acid so $...
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What is the pH of starch?

We need to identify an unknown for a chemistry lab. It's either starch or zinc sulfate. We know that zinc sulfate is acidic, but what is the pH of starch?
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Finding pKa from equivalence point on titration curve [closed]

Is there a mathematical proof/explanation of why $\mathrm{p}K_\mathrm{a}$ corresponds to the $\mathrm{pH}$ at $\text{Volume of titrant}/2$ at the equivalence point? A concise proof will suffice.
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Why does gaseous HCl not change dry blue litmus paper to red?

I am doing a practical in lab, in which HCl is to be evolved. I found that when blue litmus is near the evolved gas, it doesn't turn red. But, when litmus is dipped in water and then brought near the ...
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Calculating PH of solution after adding strong acid (equilibrium)

Consider the classic example when talking about acids and bases: Say you have 1M of $\ce{HCL}$ and you throw it into water, calculate the resulting pH (= concentration of $\ce{H3O+}$). The way this ...
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1answer
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Determining volume of acid needed to be added to reach a specific pH

Suppose there are $\pu{0.024}$ moles of $\ce{Na2HPO4}$ in a $\pu{0.250L}$ solution. How would we calculate the amount of $\pu{0.145M}$ $\ce{HCl}$ needed to reach a $\mathrm{pH}$ of 6.60? I have ...
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Find the concentration of proton after adding a acid to NaOH [closed]

I have this simple problem that I cannot figure out though, only the first part. 100 ml of 1.0 $\frac{mol}{L}$ $NaOH_(aq)$ contains ( a ) g of NaOH. After mixing 100 ml of 1.0 $\frac{mol}{L}$ $...
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What mass of potassium lactate is needed to 300.0 mL of 0.238 M Lactic acid solution to make a solution with a pH of 4.00? pKa (lactic acid) =3.86

Upon attempt, I've yielded an answer of 11.91g. My calculations do not take 300 mL Lactic acid solution into account, and now I somewhat know the error is at least partially due to the fact that my ...
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1answer
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How to calculate the amount of citric acid to neutralise the pH within wastewater?

We have an effluent tank, with a consent to discharge at between 5.5 - 11 pH, the tank holds 100000 liters of dirty water. When the pH reaches 10.5 we add citric acid to bring the pH down. How ...