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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1answer
1k 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
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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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1answer
411 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
119 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
117 views

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
233 views

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
4k views

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 ...
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1answer
171 views

Finding concentration and moles given final and initial pH

Questions: How many moles of $\ce{NaOH}$ are needed to change $500~\mathrm{L}$ of solution with $\mathrm{pH}\ 2$ to $\mathrm{pH}\ 11$? A swimming pool contains 2 million litres of water at $\...
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What does 0.12 N mean on a bottle of sulfuric acid?

I just bought a bottle of sulfuric acid in order to simulate acid rain for an experiment. I was wondering what $0.12\:\mathrm{N}$ on the bottle means. I need a simplified version of the explanation as ...
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1answer
2k 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. ...
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1answer
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Composition and pH of water produced by air conditioners

I would like to know if there are specific studies or research regarding the condensed water that is generated by air conditioners. Many people feel that this water is acid and corrosive but could ...
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1answer
728 views

Does higher [OH] not entail higher pH?

A student has equal volumes of $\pu{1.0 mol dm-3}$ sodium hydroxide and ammonia solutions. Which statement about the solutions is correct? A. Sodium hydroxide has a lower electrical conductivity ...
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4answers
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Is LiOH a weaker base than NaOH?

Is LiOH a weaker base than NaOH? Note: I'm not interested in "why," but rather what the "real" pKb values are. $$ \begin{array}{lcc} \text{Data for Alkali Metal Hydroxides} \\ \hline \text{Cation} &...
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1answer
646 views

What happens to a quaternary ammonium cation at a pH above its pKa?

I am working with a lipid and I have firm reasons to believe that its pKa is around 8. This lipid is a cationic lipid where the nitrogen is a quaternary amine with two lipid chains and two methyl ...
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0answers
753 views

Calculating the pH of a solution of sodium carbonate

I've seen similar questions on this site, but I'm having trouble as my book said something else. For a $\pu{0.09989 M}$ solution of $\ce{Na2CO3}$, my book said: $$\ce{Na2CO3 + 2H2O -> H2CO3 + 2Na+ ...
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2answers
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Does salinity affect seawater's pH?

If so, how? It seems like excessive salinity within seawater has the same destructive effect on marine organisms just like excessive acidity. But in real terms, is there any relation between salinity ...
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1answer
217 views

What is the citric acid concentration, [HCit], in the lemon juice?

The pH of lemon juice is about 2.1. What is the citric acid concentration, [HCit], in the lemon juice? I am given that $HCit \leftarrow \rightarrow H^+ + Cit^-$ and that $K_a = 8.4 \times 10^{-4}$. ...
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2answers
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What is the ionization constant, $K_a$, of the acid?

A 0.45 M solution of a weak acid, HX, has a pH of 4.5. What is the ionization constant, $K_a$, of the acid? Attempt at solution: [HX] is already given as 0.45 M. [H+] is given by $10^{-4.5}$. ...
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0answers
400 views

Does negative pH mean it is a stronger acid than one with positive pH?

I've searched this site but I don't think this has been asked yet. Does negative pH indicate a stronger acid than a positive pH (since it's further down the scale)? I'm asking this because in one of ...
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2answers
9k views

Calculation of the pH of a mixture of a strong acid and weak acid

The question is to find out the $\mathrm{pH}$ of a mixture of weak acid and strong acid. My book just states the formula as $$\mathrm{pH}=-\log \frac{C_2+\sqrt{C_2^2+4K_\mathrm{a}C_1}}{2}$$ where $...
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3answers
36k views

pH range outside conventional 0-14 [duplicate]

Is a pH value outside 0 - 14 possible? I asked my teacher who said: yes, it is, but very difficult to achieve. Then on the internet, I found multiple answers, one saying it is but because of a fault ...
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1answer
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What's the difference between isoionic point and isoelectric point?

What's the difference between isoionic point and isoelectric point? My teacher uses them interchangeably, but Wikipedia states that isoionic point is when charges are balanced, while isoelectric point ...
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0answers
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Is endpoint pH concentration dependent? Choosing an acid/base indicator

We use titrations to determine analyte concentrations with a standardized titrant and an acid/base indicator, BUT how do we choose the indicator? It is my understanding that indicators are supposed to ...
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1answer
101 views

What is the true formula of pH scale? [closed]

I'm learning Acid and Base at school, and I have a confusion in that topic. The $\mathrm{pH}$ scale is measure of the $\ce{[H+]}$ in a solution. So why is its formula $-\log(\ce{[H+]})$? I don't ...
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Why does CO2 lowers the pH of water below 7?

Ok so I understand that having a pH below 7 is considered to be acidic and I also understand that part of the definition of an acid is that it gives off H+ when dissolved in water(even though not all ...
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0answers
160 views

Henderson-Hasselbalch approximation

The Henderson-Hasselbalch approximation gives us a method to approximate the pH of a buffer solution. The basic equation is as follows: $$\mathrm{pH} \approx \mathrm{p}K_\mathrm{a} + \log\dfrac{\ce{[...
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1answer
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Does the pH of Water affect how Acidic or Basic it is?

I've noticed a lot of people have been recently uploading videos in which they test the pH of multiple brands of bottled water and claim that the more acidic ones (5.5 < pH < 6.5) are worse for ...
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3answers
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How does pH change during the electrolysis of water? [closed]

How does the pH change during electrolysis of a water and magnesium sulphate solution? Also, will this pH change happen every time? Does the pH change differently when there is just water in the ...
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2answers
202 views

Best way to raise pH without alkali metal? [closed]

I have a process that requires pH~14-14.5 to work. I’ve been achieving this with concentrated NaOH solutions, but the Na cations are later causing side reactions which are detrimental. Is there any ...
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1answer
685 views

What is the charge of the amino acid lysine at pH 2?

What is the charge of the amino acid lysine at $\mathrm{pH}=2$? $\mathrm{p}K_\mathrm{a}$'s are carboxylic: 2.18; amino: 8.95; side chain: 10.79. The side chain of lysine is an amine group, so I ...
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1answer
104 views

What is so special about positive hydrogen ions that they are used in pH calculation?

I just learned about pH. If I understand it correctly, all it really tells is the concentration of positive hydrogen ions (protons) there are in a given liquid. Why is this pH scale entirely ...
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1answer
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Why does pOH increase when pH decreases?

Let's say you add $\ce{HCl}$ to water. The $\ce{H+}$ ion concentration increases and that causes a decrease in $\mathrm{pH}$. But why would the $\mathrm{pOH}$ increase? I can't see why added $\ce{H+}$...
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1answer
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Difference in pH of water and rainwater

In my textbook (Olmsted and Williams 4th ed) it is given that pH of pure water is 7, pH of unpolluted rain water is between 5-6 and pH of acid rain is between 4-5. It is obvious that pH for acid ...
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1answer
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Find the half equivalence point

How to find the half equivalence point knowing the pH, molarity, titrant added at equivalence point? This a fairly straightforward and simple question, however I have found many different answers to ...
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1answer
214 views

Numerical on acetic acid - sodium acetate buffer

Starting with 1 L of 2.0 M $\ce{CH3COOH}$, we wish to make a buffer solution of pH=4.00. Consider two ways to make the buffer: a) One way would be to add sodium acetate. How many moles must be added?(...
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1answer
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Titration of sodium carbonate and nitric acid

I am trying to find the pH of the following problem (Answer key is $\mathrm{pH}=10.77$) Calculate the $\mathrm{pH}$ of a $\pu{100 mL}$ solution containing $\pu{40.0 g}$ of $\ce{Na2CO3}$ after $\...
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1answer
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pH value of a very dilute alkaline solution [closed]

What is the pH of a $\pu{10^-9 M}$ $\pu{NaOH}$ solution? I think it is 5.
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Computation of pH when an acid and base are mixed in solution

I'm doing a basic chemistry course, and we are currently learning how to compute $\text{pH}$ from the acid dissociation constant (using $\left[\text{H}^{+}_{(\text{aq})}\right]=\sqrt{K_{a}\left[\text{...
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1answer
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Deriving the buffer formula

Essentially I want to derive the buffer formula: $\ce{pH}$ = $\mathrm{p}K_\mathrm {a}$ + $\log$ $\left(\frac{\alpha}{1-\alpha} \right)$ to $\alpha$ = $\left(\frac{1}{10^{\mathrm{p}K_\mathrm{a}-\ce{pH}}...
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2answers
330 views

Equilibrium constants for lewis acids such as Ca2+

I need to calculate the theoretical $\mathrm{pH}$ in a $50~\mathrm{mL}$ water solution where $6.4\times10^{-4}~\mathrm{g}$ of $\ce{Ca^{2+}}$ is present. The reaction I base this on is the following $$...
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1answer
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Why was my soap measured as acidic?

I've always been told soap is basic in pH. A few years back in a high school chemistry class, we measured the pH of various substances with universal pH indicator. We measured some liquid hand soap ...
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3answers
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pH and materials selction [closed]

I working on the Navy study guide for their nuclear engineering programs and I am not a Chemist. Thus, I have come here to try and develop a better understanding of the subject matter. Why is pH ...
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pH of dilute HCl solution

What is the pH of a solution of $3.4 \times 10^{-10}$ moles of $\ce{HCl}$ in a volume of $\pu{150.7L}$? This is dilute so I expect pH to be high. $$\frac{3.4 \times 10^{-10}\ \mathrm{mol}}{150.7\ \...
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What is the pH of ice?

The pH of pure liquid water depends on temperature. It is about pH = 7.0 at room temperature, pH = 6.1 at 100 °C, and pH = 7.5 at 0 °C. What happens to the pH (or to the ion product) of pure water ...
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If the pH is zero, what would be the normality of a sulphuric acid solution?

If pH of the solution is zero, what would be the normality of $250 \, \mathrm{ml}$ $\ce{H2SO4}$ solution? My work: $\mathrm{pH} = 0$, hence the concentration of $\ce{H+}$ ions is $\pu{1 mol L^-1}$, ...
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2answers
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Calculating the pH of a dilluted aqueous KOH solution

Calculate $\mathrm{p}\ce{H}$ of an aqueous solution of $0.01\:\mathrm{nM}~\ce{KOH}$ in water. I think that water also has $\ce{OH-}$ ions in concentration of $10^{-7}\:\mathrm{M}$ (since $\mathrm{p}\...
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1answer
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How to calculate the pH of a 0.325 M solution of pyridine hydrofloride?

How to calculate the $\mathrm{pH}$ of a $0.325~\mathrm{M}$ solution of $\ce{C5H5NHF}$? The $K_\mathrm{b}$ for $\ce{C5H5N}$ and $\ce{C5H5NH+}$ is $1.7\times 10^{-9}$. Here's my work, but it's wrong (...
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Does NaOH have a higher OH- concentration than NH3?

In my book it's a multiple choice question with only one correct answer. There are two solutions of $\ce{NaOH}$ and $\ce{NH_3}$ that have similar concentrations and volumes. These two are among ...
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1answer
535 views

pH of aqueous very dilute hydrochloric acid

Calculate the $\mathrm{pH}$ of pure water in which $\ce{HCl}$ was added. The final concentration of $\ce{HCl}$ is $\pu{10^{-6}M}$. So what I did was to add the concentration of $\ce{H3O+}$ in pure ...