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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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
718 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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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
606 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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721 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
196 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
139 views

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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388 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
2k views

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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87 views

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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154 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
44 views

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
3k views

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
188 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
658 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
1k views

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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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
3k views

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
212 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
2k views

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
302 views

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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3answers
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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
124 views

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
329 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
477 views

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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2answers
14k views

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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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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1answer
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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
530 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 ...
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1answer
87 views

Why is the combination of hydrated aluminium oxide and magnesium hydroxide used to treat heartburn?

Why is the combination of hydrated aluminium oxide and magnesium hydroxide used to treat heartburn? I get why $\ce{Mg(OH)2}$ would be used since its a strong base and is badly soluble in water. Thus ...
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Alternatives to EDTA for calcium ion chelation

Are there any $\ce{Ca^2+}$ chelating agents (other than EDTA) that are as good as EDTA in terms of binding calcium ions and effective in a pH range of $5$ to $9$?
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1answer
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Determination of pKa by absorbance and pH of buffer solutions

I've been tasked (as part of a report) to calculate the $\mathrm pK_\mathrm a$ of 4-nitrophenol by measuring the pH and absorbance of six 'buffer solutions' containing the 4-nitrophenol: $$\begin{...
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1answer
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Why is the pH scale only from 0-14? [duplicate]

Why can't there be more hydrogen ion concentration in acids or lesser hydrogen ion concentration in bases? Why should there even be any hydrogen ion concentration in alkalis? (I know pH is calculated ...
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1answer
98 views

Why can we ignore the weak conjugate base/acid when calculating the pH in a titration problem? [closed]

Take the reaction 350 mL of 0.8M HCN and 0.6M NaOH for example. The problem asks us the calculate the pH when we add 500 mL of 0.6M NaOH into the 350 mL of 0.8M HCN (This is more than enough to ...
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1answer
99 views

pH calculation of HK2PO4

I am struggling with a calculation I should know how to do, but I feel like I may be missing crucial information. Here's the outline: I dissolve $\pu{6.0 g}$ of $\ce{HK2PO4}$ in $\pu{20 mL}$ of water....
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4answers
50k views

Shouldn't the pH at the equivalence point always be 7?

I learned in class that the equivalence point in an acid-base titration is reached when the solution contains an equal amount of substance of $\ce{OH-}$ and $\ce{H+}$ ions. However, in a weak acid and ...
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2answers
1k views

Relating pH and buffer capacity

So, here is the equation for a weak acid - strong base pH curve And here is the expression gotten when the derivative of concentration of hydronium ions with respect to volume of base added is ...
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1answer
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pH value of distilled (pure) water [duplicate]

What is exactly the pH value of distilled water? which is correct? Neutral(not acidic not alkaline)pH 7? pH 6?
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2answers
751 views

How can one calculate the pH of a solution?

So, I have 1 litre of acetate buffer, and 0.1 mol of oxonium ions/$\ce{H3O+}$ is added. The task is to calculate the pH of this solution. What I was thinking: $$\ce{CH3COOH + H2O <=> CH3COO- + ...