Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [ph]

pH (or the potential of hydrogen) is a scale used to measure how acidic or basic an aqueous solution is.

0
votes
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. ...
0
votes
0answers
31 views

Buffer/ Indicators / % protonated

I have a buffer with a pH of 5. First I need to find what indicator to use. My options are (Thymol Blue - $\mathrm{p}K_\mathrm{a} = 8.9$), (Bromothymol Blue- $\mathrm{p}K_\mathrm{a} = 7.1$), or (...
0
votes
2answers
682 views

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 ...
1
vote
1answer
306 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 ...
0
votes
0answers
435 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+ ...
2
votes
2answers
934 views

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 ...
-3
votes
2answers
102 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 $10^{-4.5}$. ...
0
votes
1answer
135 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 $K_a = 8.4 \times 10^{-4}$. ...
1
vote
0answers
204 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 ...
-1
votes
1answer
981 views

Calculating the pH upon titrating barium hydroxide and hydrochloric acid

Question: Calculate the pH produced from mixing $\pu{25.0 mL}$ of $\pu{0.420 M} $ $\ce{Ba(OH)_2}$ with $\pu{125 mL}$ of $\pu{0.120 M}$ $\ce{ HCl}$. Attempt: I'm learning about acids and bases ...
3
votes
1answer
883 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 ...
1
vote
0answers
44 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 ...
0
votes
0answers
79 views

How much sodium hydroxide powder do I need to add to get a new pH?

I want to increase the pH of a $\pu{300 ml}$ deionised water solution from 7 to 11. How much sodium hydroxide should I add? I have tried this but the answer doesn't seem correct (because it's so small)...
0
votes
0answers
28 views

How does a glass pH electrode measure potential difference? [duplicate]

I think I have a basic understanding of how an ion-selective electrode (in particular the pH electrode) works. I've read that section of Harris's Quantitative Chemical Analysis many times. The gap ...
-1
votes
1answer
91 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 ...
-1
votes
2answers
223 views

How to make a pH 6.8 Tris buffer?

To preface this, I am a biologist. I need to make a $\mathrm{pH}=6.8$, $\pu{1 M}$ Tris buffer. We have access to Tris base and Tris Hydrochloride. (Unfortunately, none of the fancy Tris compounds ...
1
vote
0answers
123 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{[...
-1
votes
1answer
42 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 ...
1
vote
3answers
1k 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 ...
1
vote
1answer
349 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 ...
0
votes
2answers
120 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 ...
1
vote
1answer
88 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 ...
3
votes
1answer
814 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 $\ce{H+}$...
-1
votes
1answer
988 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 ...
-1
votes
1answer
140 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?(...
-2
votes
1answer
187 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.
1
vote
1answer
191 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 ...
0
votes
1answer
5k views

Why are limes alkaline, but lemons are acidic? They taste about the same [closed]

So, this is kinda a dumb question, but I'm curious.
2
votes
0answers
76 views

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 $9$?
-2
votes
1answer
45 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 ...
0
votes
1answer
2k views

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 ...
0
votes
1answer
85 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....
1
vote
1answer
241 views

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{...
0
votes
0answers
23 views

Significance of Hydrogen ion activity in pure water when considering pH

So I've read this regarding the pH level of pure water at different temperatures, but the answer only considers that the pH of the pure water is equal to the negative log of the concentration of the ...
-1
votes
1answer
2k views

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?
-1
votes
1answer
930 views

pH value change with dilution

How does pH value change with dilution for the question shown in the picture? I expect the pH value to increase with dilution. Is there any case where the value remains same with dilution?
4
votes
2answers
383 views

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 $\...
3
votes
2answers
943 views

Why does pH change with temperature? [duplicate]

Why does pH change with temperature? I recently read up on some chemistry notes, and found out that the higher the temperature of distilled water, the lower the pH. Why? Does this apply to other ...
3
votes
1answer
61 views

Dissociation constants of leucine

Leucine is a type of amino acid. Let me write its chemical formula as $\ce{NH2-C5H10-COOH}$. On the wikipedia page, https://en.wikipedia.org/wiki/Leucine, there are two dissociation constants, one for ...
-1
votes
1answer
42 views

Redox - concentration cell

I'm studying galvanic cells and I've found a demonstration that lead me to an impossible result, so there must be a mistake, but I can't find what it is. My problem is about concentration cells made ...
-1
votes
1answer
204 views

calculating ph of a mixture of acids

I came across a question that couldn't find the answer to and i couldn't find the answer anywhere. The question is the following. You have a soltion created by dissolving HCN and HBrO in water (T = ...
0
votes
2answers
109 views

Weight of sodium acetate required to get to certain pH

How many grams of $\ce{CH3COONa}$ we need to dissolve in $\pu{2.50 L}$ of water to get a solution with $\mathrm{pH} = 9.00$? Given $K_\mathrm{a}(\ce{CH3COOH}) = 1.75\cdot 10^{-5}$ Like solving a ...
2
votes
1answer
767 views

Mixing Ca(OH)2 with Ca(NO3)2

Mixing $\ce{Ca(OH)_2}$ with $\pu{0.1 M}$ concentration of $\ce{Ca(NO3)2}$. What will actually happen in the process? What I will see with my eyes? I know that $\ce{Ca^2+}$ cation with concentration ...
3
votes
0answers
1k views

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 ...
-1
votes
1answer
43 views

Can i calculate the solution of the problem in more simple way?

and i got a serious question. During my exercises at home, i found that im struggling a lot while solving simple problem`s like this one: I have an aquatic substance with 0.100 M of $\ce{Mg(NO3)2}$ ...
3
votes
0answers
216 views

What pH indicators are commonly used for non-polar medium?

Compounds, commonly used as pH-indicators, are soluble in aqueous media and polar solvents (DMSO, DMF, NMP etc.) and are functional pretty much across all these solvents. However, practically none ...
3
votes
1answer
487 views

Calculating the pH of a ammonium hydrogen sulfate solution

I am attempting to complete a question in which I need to use an ICE table to calculate the pH of a $\pu{2.61 mol L-1}$ $\ce{NH4HSO4}$ (ammonium hydrogen sulfate) solution. When $\ce{NH4HSO4}$ ...
-1
votes
1answer
787 views

Blue litmus turning pink

I just read that carbonic acid turns blue litmus pink and not red. Is it just because it is a weak acid. What about organic acids then? How do they respond to the litmus test? If strength and ...
1
vote
2answers
964 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 $\mathrm{pH}$?
3
votes
1answer
7k views

What is exactly the pH value of distilled water?

This was asked by one of my students in my class. I know it is the pH of 7, but others say it can be 6.55 pH