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 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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0answers
15 views
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 ...
1
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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
$$\ce{[H^+] =\frac{[...
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0answers
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Why do some cations and anions interact with water to form corrresponding acids and bases(hydrolysis)? [duplicate]
I have seen in my textbook that on cations/anions formed on ionization of salts either exist as hydrated salts in aqueous solutions or interact with water to reform corresponding acids/bases depending ...
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2answers
42 views
Calculating dissociation degree from pH and Ka without given initial acid concentration
Is it possible to calculate the dissociation degree (DD) from pH and Ka without directly been given the initial acid concentration?
I found the following formula:
$$\text{DD} = \frac{K_\mathrm{a}}{...
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0answers
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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
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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
27 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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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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0answers
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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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How to find the pH for a very diluted HCl solution? [duplicate]
Yesterday my chemistry professor asked us to try to solve this problem.
Find the pH of this reaction: $$\ce{HCl + H2O -> H3O^+ + Cl^-}$$
Knowing that:
The volume of the solution is 1 liter.
...
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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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3answers
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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
122 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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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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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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1answer
38 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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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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1answer
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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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2answers
33 views
Does a solution of pH zero contain hydroxide ions? [closed]
Are there hydroxide ions in a solution of pH 0?
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1answer
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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
47 views
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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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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1answer
33 views
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, ...
2
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0answers
36 views
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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0answers
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How to measure pH of deionized water
reverse osmosis deionized water (RODI) is used to rinse acid off silicon after it undergoes silicon etching. Sample of water is taken and measured by using pH meter. However, pH meter takes a 1-2 ...
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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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1answer
48 views
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
276 views
How to calculate pH of the Na2Co3 solution given ambiguous Ka values
This is the exact question i faced on 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{Na2CO3 -&...
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If Ti(NO3)4 is dissolved in water, what would be the change of pH?
Does this compound exist in nature. I would suppose the salt would dissolve in it's ions (Nitrate and $\ce{Ti+}$). Wouldn't the nitrate react with the hydrogen in the water and give us a acid? And ...
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2answers
262 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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1answer
83 views
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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0answers
55 views
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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2answers
300 views
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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0answers
37 views
Capacity of buffer
I want to dissolve 23 mg of EDC (N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride) in MES buffer with pH=6. How can I know the amount and concentration of MES buffer which can keep the pH=...
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1answer
40 views
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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1answer
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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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1answer
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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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1answer
244 views
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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1answer
2k views
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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Buffer solutions
So my understanding of buffer solutions is that when a strong acid is added, it will react with the conjugate base to convert the strong acid to a weak acid. The weak acid then dissociates to reform ...
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1answer
251 views
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
78 views
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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1answer
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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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1answer
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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
1k views
pH value of HF, hydrogen fluoride or hydrofluoric acid?
I've been looking for a source but I find different results when I try looking for an answer to this.
I'm looking for weight percentages of 1 to 10% HF (~0.5 to ~5.1M) and what their pH values are.
...
