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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33 views

How identify acid and base for Henderson-Hasselbach equation [closed]

If I am asked to determine the pH in e.g. 60 mM Na2CO3 and 30 mM NaHCO3 or 50 mM NaHSO4 and 40 mM Na2SO4 How do I go about to identify which of these two is the base and which is the acid? ...
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79 views

Why is the pH level of carbonation loss decreasing then increases afterwards?

We have done an experiment of the titration of unsealed sprite soda to find the amount of carbonic acid being loss on various duration (0 to 1 hour), due to decrease pressure. The calculation was to ...
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30 views

Finding the molarity of an unknown weak acid when its pH and volume is given

In lab we measured the pH of $\pu{25.0 mL}$ of an unknown acid. The pH was $2.43$. I’m supposed to figure out the molarity. How? I don’t know the $K_a$ or anything. Volume seems useless. I really just ...
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1answer
25 views

How was the ionization constant of water found? [closed]

We were just starting to learn about pH in school recently and we learned that $K_w$ is a constant at $\pu{298 K}$ and it's equal to $10^{-14}$, the teacher said this could be found experimentally but ...
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10 views

How to calculate the amount of solid soda added to increase the pH of a solution [closed]

0.1 mole of HCN and 0.01 mole of AgI are in solution in 1 litre of water. We add solid soda to increase the pH of the solution. Ka(HCN/CN-)=10^-9.2 Ks(AgI)=10^-16 KD(Age(CN)^- 2)=10^-21 When the AgI ...
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1answer
36 views

Dilution of Ca(OH)2 and its pH [closed]

A basic solution of Ca(OH)2 was diluted until a final concentration of 10^-9 M. What is the pH?
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33 views

Is menthol in aqueous solution acidic or alkaline? [closed]

I was wondering whether the menthol added in common "mint based" chewing gum has a potentially acidic nature. I can't seem to find any answers for this via a web search.
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2answers
131 views

Calculating pH of rain water

The concentration of $\ce{SO2}$ in the atmosphere over a city on a certain day is $\pu{10 ppm}$. Given that solubility of $\ce{SO2}$ in water is $\pu{1.3653 mol L-1}$ and $\mathrm{p}K_\mathrm{a}$ of $\...
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21 views

How do you find the ph of lime juice through titration?

I am doing an experiment on the effect of time on the pH of Lime juice. I was wondering how you would calculate the pH through titrations using 1 Molar NaOH. I have been racking my brain on this for a ...
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1answer
33 views

Why does the concentration of the acid equals that of the base at the mid-point of titration? [closed]

Consider this graph of the titration of a weak acid and a strong base: The buffering region is strongest at the midpoint of titration because there is equal concentrations of acetic acid and its ...
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2answers
83 views

Why is H⁺ ion considered the source of acidity, and OH⁻ considered the source of basicity? [closed]

As the title implies, what caused the association between $\ce{H+}$ and acidity, and between $\ce{OH-}$ and basicity?
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68 views

Can Acids have pH of more than 7? [duplicate]

Consider a solution of $\text{HCl}$ with a concentration of $10^{-10}$ $\text{M}$. Now, if I find it's pH: $$\begin{aligned}\text{pH} &= -\log([\text{H}^+])\\ \text{pH} &= -\log(10^{-10}) = 10\...
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29 views

How will the dielectric constant of water change when ethyl acetate is added?

How will the dielectric constant of water change when ethyl acetate is added? The $\mathrm{p}K_a$ value of weak acids in aprotic solvents will be lower than in protic solvents because the dielectric ...
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1answer
46 views

Finding Ka of a monoprotic weak acid from pH and concentration of added sodium salt

A solution of $\pu{0.36 M}$ of the sodium salt of a generic monoprotic weak acid $\ce{HA}$ has a $\mathrm{pH}$ value of $8.782.$ $K_\mathrm{a} = ?$ Why doesn't the following formula work in this ...
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1answer
53 views

Accurate method to calculate the pH of a salt from a weak acid and weak base

Can someone help me with this? The problem is as follows: Find the $\mathrm{pH}$ of $\pu{1M}$ solution of $\ce{NH4CN}$. Their respective hydrolysis constants are: $K_h = 5.6\times 10^{-10}$ ...
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1answer
78 views

pH After titration

$\pu{50mL}$ $\ce{SO2}$ titrated with $\pu{0.1M}$ of $\ce{KBrO4}$ with reaction: $$\ce{KBrO4 + 4SO2 + H2O -> 4H2SO4 + KBr}$$ The equivalent point is reached when the volume of $\ce{KBrO4}$ is ...
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3answers
81 views

Tap water pH adjustment using citric acid

I've lowered tap water pH from 7 to 6 using citric acid. After couple of hours pH raised again to 7. What is the reason for this raise? Citric acid overcomes waters buffering feature then raise the $...
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2answers
2k views

How does pH affect the degradation of ascorbic acid (vitamin C)?

I know that vitamin C degrades over time (as I understand through oxidation). However, I am having trouble understanding how changing the pH of the solution in which the vitamin C is affects the rate ...
12
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1answer
5k views

Is the equation pH + pOH = 14 valid at different temperatures?

$\mathrm{pH} + \mathrm{pOH} = 14$ For water at 60 degrees Celsius, $K_\mathrm{w} = 1 \times 10^{-13} = [\ce{H+}] \times [\ce{OH-}]$ Hence, $[\ce{H+}] = 1 \times 10^{-6.5} = [\ce{OH-}]$ So $\...
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1answer
14k views

Effect of Temperature on pH of Water

The $K_\mathrm w$ is a function of temperature. It is $10^{-14}$ at $25\ \mathrm{^\circ C}$. When the temperature is $50\ \mathrm{^\circ C}$, the $K_\mathrm w$ can be calculated to be somewhere around ...
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18 views

How to find the molar concentration of two compounds mixed together in a buffer solution having the Kb and its Ph [duplicate]

Calculate how many milliliters of a $\pu{8.00 \times 10^{−1} M}$ solution of $\ce{NH3}$ and how many milliliters of a $\pu{7.80 \times 10^{−1} M}$ solution of $\ce{NH4Cl}$ are needed to get to a liter ...
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37 views

pH responsive polymer which is immiscible in water?

Can anyone suggest a pH-responsive polymer, which is immiscible in water (polar solvent) but miscible in oil (e.g vegetable oil)? I want to study the change in the density of such polymers when they ...
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1answer
216 views

“Adjust pH of the solution to 5.0±0.1 with acetic acid (by potentiometry)”

In a procedure description I'm translating, there's this sentence (I here quote it literally, word for word, as it is in Russian): Adjust the pH of the solution to 5.0±0.1 with acetic acid (by ...
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1answer
19 views

How does increasing the Hydrogen Concentration of CuSO4 (electrolyte) affect electroplating of copper

I'm trying to find an answer as to how lowering the pH of the CuSO4 solution during electroplating of copper affects the amount of copper deposited onto the cathode. My very basic understanding is ...
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1answer
200 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
48 views

Can ascorbic acid be neutralized and keep it's elastic properties in dough?

Ascorbic acid (C6H8O6) is commonly used in dough to give it strength and elasticity. However, I need this dough to be alkaline, or at the very least neutral. I've used sodium carbonate (Na2CO3) before ...
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2answers
58 views

pH of amphoteric species

For a solution of $\ce{HA-}$, I have seen the following approximations for the $\mathrm{pH}:$ $$\mathrm{pH} = \frac{1}{2}(\mathrm{p}K_\mathrm{a1} + \mathrm{p}K_\mathrm{a2})\tag{1}$$ $$\mathrm{pH} = \...
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3answers
95 views

How to simplify these system of equilibrium equations

What is the pH when $0.025$ mol $\ce{NiCl2}$ is added to $\pu{1.00 L}$ of a $\pu{0.100 M}$ solution of $\ce{HCN}$, if the formation constant for $\ce{Ni(CN)4^2-}$ is $K_f=\pu{1.0e22}$, and the $K_a$ ...
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2answers
82 views

Acidic nature of boric acid when its concentration high

Following statement was given for boric acid $(\ce{H3BO3}):$ At low concentrations $(\leq\pu{0.02 M})$ essentially $\ce{B(OH)3}$ and $\ce{B(OH)4-}$ are present, but at higher concentration the ...
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1answer
132 views

Understanding the increase in pH of a buffer solution upon incremental additions of NaOH analytically

So let's say we have $200\ \mathrm{mL}$ of $1\ \mathrm M$ $\ce{CH3COOH}$ solution. In this solution we have the equilibrium $\ce{CH3COOH <=> CH3COO- + H+}$. To that we add $100\ \mathrm{mL}$ of $...
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97k 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
56 views

Is there a relationship between acidity of the water solution and oxidation/reduction reactions?

What I want to know is if there is a relationship between the acidity of the water solution and redox reactions and if there is a relationship what favors the oxidation and what favors the reduction? ...
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Acidity comparison on R-PO3H2

Question Compare the acidity $(K_\mathrm{a1})$ of the following three acids: $\ce{H3PO4},$ $\ce{Ph-PO(OH)2}$ and $\ce{H3C-PO(OH)2}.$ Thoughts These three acids are of type $\ce{R-PO3H2},$ where ...
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130 views

Fitting multiple pKa's

I have three histidine residues that are next to each other in a protein. When I compute the fraction of unprotonated states for each individual histidine as a function of $\mathrm{pH}$ my titration ...
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2answers
160 views

Use of Concentration for pH

When we find the pH of a solution, do we use normality or molarity? My teacher said that if the compound is present by itself, we can use normality but in all other cases we should use molarity. Can ...
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1answer
5k views

How to calculate pH of the Na2CO3 solution given ambiguous Ka values

This is the exact question I faced on an 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{...
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2answers
511 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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1answer
4k views

What actually happens when citric acid is added to a highly alkaline soap solution?

A few days ago I made an experiment. I diluted a few small chunks of bar soap with 20 ml of water. I then measured the ph of the solution which was around 10. I then added a tiny amount of citric acid....
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192 views

Why does pKw first decrease but eventually increase when temperature rises?

I understand the initial decrease in pKw. $\ce{Heat + H2O (l) <=> H+ (aq) + OH- (aq)}$ Temperature increases, reaction shifts to the right, so $\ce{H+} \text{ and } \ce{OH}$ ...
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4answers
42k 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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2answers
45 views

Can I make a buffer with a weak acid without adding it's conjugated base, when the desired pH of the solution is exactly the pKa of the weak acid?

An acid will be 50% dissociated when the solution it's in have a pH equal to the acid pKa ('afirmation 1', for later reference). We also know that a good buffer solution have equal concentrations of ...
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45 views

Is contribution to pH by an acid or base always greater than salt hydrolysis?

I was solving a titration question and the reaction I came to was this: $$ \begin{array}{lcccc} \ce{&BOH(aq) &+ &HCl(aq) -> &BC(aq) &+ &H2O(l) }\\ \text{Initial} & x &...
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How to clean pocket pH meter before storage?

Hello. I read about different methods how to clean this specific(attached photo)pocket pH meter before storage and i can't figure out what is the right way. One method says to stir the pH meter(...
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2answers
3k views

Relationship between pH and volume

I had prepared two different volume of solution: $\pu{500 mL}$ and $\pu{100 mL}$ with same concentration ($1\%$), but I obtain different $\mathrm{pH}$. Will volume affect $\mathrm{pH}$?
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1answer
88 views

pKa of phenols using UV-Vis spectroscopy

I have done an experiment where I dissolved four different substituted phenols in acidic, basic, and buffer solutions, and recorded the UV-Vis spectra for each. I'm supposed to pick a wavelength where ...
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0answers
68 views

What is the pH and pKa relationship of LaCl3 in water and its precipitant La(OH)3?

In light of this question and its answers, I hope to get some insights into the $\mathrm{pH}$ of $\ce{LaCl3}$ in water and its $\mathrm{pH}$ relationship to $\ce{La(OH)3}$ precipitant's $\mathrm{p}K_\...
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1answer
77 views

How to calculate the number of protons in a sphere given the volume and the pH?

The spherical radius of a nano-droplet of a solution ($\mathrm{pH}$ of which is $6$) is given as $\pu{20nm}$. I can find the molar concentration of $\ce{H+}$ and subsequently the number of $\ce{H+}$ ...
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2answers
1k views

How to calculate the composition of a borate buffer with a defined pH using the Henderson-Hasselbalch equation?

I am struggling with what appears to be an extremely easy pH problem that uses the Henderson-Hasselbalch equation. The problem and answer provided by the book is given below. I understand where the ...
6
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3answers
2k 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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51 views

Hydronium ion concentration to compare pH values

I'm having a bit of trouble with this question: Which has a higher $\mathrm{pH}$ value, $\pu{0.001 M}$ $\ce{HCl}$ or $\pu{0.1 M}$ $\ce{CH3COOH}$ $(K_\mathrm{a} = \pu{1.8E-5})?$ I have calculated ...

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