Questions tagged [ph]

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

Filter by
Sorted by
Tagged with
3
votes
2answers
3k views

Why does p mean −log(x)?

$\mathrm{pH} = -\log[\ce{H+}]$ while $\mathrm{pOH} = -\log[\ce{OH-}]$ Why does $\mathrm p$ represent $-\log$ of something? Is it due to some historical reason or due to some scientific reason?
3
votes
2answers
118k views

What is the pKa Range for weak acids and bases?

Am I correct in assuming that the following is true? $\mathrm pK_\mathrm a < 3$ is for a strong acid $3 < \mathrm pK_\mathrm a < 7$ is for a weak acid $7 < \mathrm pK_\mathrm a < 11$ ...
3
votes
2answers
727 views

Why do we neglect the protons from water's autoprotolysis?

Why don't we need to consider the $\ce{H+}$ ions of water when finding the $\ce{pH}$ of $0.01~\mathrm{M}$ of $\ce{HCl}$ solution? The $\ce{pH}$ value of something is depending on the molarity of $\ce{...
3
votes
3answers
596 views

Why does dissolving a salt in water get a high pH?

I dissolved some sodium carbonate in water and I measured the $\mathrm{pH}$. It turned out to be 11. I don't really understand why dissolving it in water increased the $\mathrm{pH}$. I mean, I know ...
3
votes
3answers
1k views

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 ...
3
votes
3answers
100 views

Why are many chemical relationships logarithmic?

I've noticed that in many relationships in chemistry, one variable is linearly related to the logarithm of another. Why is this the case? For example, I carried out an experiment where the dependent ...
3
votes
2answers
13k views

Is it true that a pH higher than the pKa of an acid make the H automatically disassociate?

Will the hydrogen atom always disassociate if the pH of the solution is higher than the pKa of the acid?
3
votes
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 ...
3
votes
1answer
1k views

Why doesn't a neutral solution at any temperature have pH 7?

I am given 4 statements to choose from and find which is correct about a neutral solution: $K_\mathrm{w} = \pu{1.00\times10^-14 mol^2 dm^{-6}}$ The solution contains only $\ce{H2O}$ $\ce{[H+] = [OH-]...
3
votes
1answer
139 views

Impossible pH For Aqueous Weak Acid Solution

An aqueous solution of $\ce{HCl}$ has a $\mathrm{pH}$ of $0.00$ if $[\ce{H+}] = 1.00 \; \mathrm{M}$. I tried to see if an aqueous solution of acetic acid could have a $\mathrm{pH}$ of $0.00$, given ...
3
votes
1answer
358 views

pH Curves for Titrations

Why does the pH rapidly increase near the equivalence point during--why does the slope of the graph of a pH curve sharply increase around this area?
3
votes
1answer
2k views

Calculations for making a buffer from a weak base and strong acid

How many moles of $\ce{HCl}$ must be added to $\pu{100 ml}$ of a $\pu{0.100 M}$ solution of methylamine ($\mathrm pK_\mathrm b = 3.36$) to give a buffer having a $\mathrm{pH}$ of $10.00$? (The answer ...
3
votes
1answer
165 views

Effect of pH on Dilution of HCl Solution

Q. A solution of $\ce{HCl}$ has a $\mathrm{pH}$ of $5$. If $1\ \mathrm{ml}$ is diluted to one litre of water at $\mathrm{pH}=7$. What is the $\mathrm{pH}$ of the resulting solution. Attempt- $$\...
3
votes
1answer
3k views

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 ...
3
votes
3answers
3k views

Phenolphthalein as a indicator for the titration of benzoic acid

Question: Justify the use of phenolphthalein $(\mathrm{p}K_\ce{in}=9.4)$ as a indicator for the titration of benzoic acid $(K_\mathrm{a}=6.3\times 10^{-5})$ with $\ce{NaOH}$. My attempt: I can ...
3
votes
1answer
439 views

Mechanism of pseudo buffer pH maintenance

Some solutions, like concentrated HCl, act as buffers even though they lack the buffering component. What is the cause for such a behaviour?
3
votes
1answer
2k views

Acidic and alkaline salt solutions: why do some salt form acid/bases while others don't [closed]

I have a question regarding salts and their solutions. How come some salts, like sodium carbonate and ammonium chloride, produce acids/bases when dissolved in water? Moreover, how can you predict ...
3
votes
2answers
14k views

Caffeine dissolution

I am looking to add caffeine powder in pure form to water that has a pH level of 7 or higher. What would the pH level be if I do this? Is Caffeine itself acidic?
3
votes
3answers
5k views

How is seawater alkaline?

If when water and carbon dioxide react they form carbonic acid, carbonate, and bicarbonate, how does seawater still have a pH of around 8? Doesn't a compound need an hydroxide ion to be a base?
3
votes
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 ...
3
votes
2answers
12k views

Why will a strong acid neutralize as much base as a weak acid?

This is a simple concept that I can't seem to understand. Why will a strong acid neutralize as much base as a weak acid, if the acids are of the same volume and concentration? A strong acid will ...
3
votes
2answers
1k views

Can Henderson-Hasselbalch equation be used to determine the pH of a solution when a strong base and a strong salt of that base stay together?

The following problem I have stated was not given to me as a homework. I have found this one in my textbook. I have solved it in my own way, but I'm not sure about the correctness of my procedure. I ...
3
votes
2answers
27k views

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

A 100 ml $\ce{HCl}$ solution has a pH of $3.7$. You want the solution to be of pH 4.5. You have a solution of $10\ \mathrm M$ $\ce{NaOH}$. How much $\ce{NaOH}$ do you need to add to to the $100\ \...
3
votes
2answers
10k views

Solution for storing a glass electrode

What kind of storage solution is required for a glass electrode? Is 3 M $\ce{KCl}$ sufficient for this purpose? If so, what is the approximate pH of that solution (the solution I use presently has a ...
3
votes
2answers
7k views

About pH of an aqueous solution of SO2

Probably we can have an aqueous solution of $\ce{SO2}$ by dissolving it in water, because we would have an equilibrium between $\ce{SO2(g)}$ and $\ce{SO2(aq)}$: $$\ce{SO2(g) <=> SO2(aq)}$$ How ...
3
votes
2answers
841 views

Find amount of acid and base required to make buffer

I am wondering if it is possible to know exact amount of acid and base that we can put in together to make a buffer. I want to make a 0.05 M extraction buffer using disodium hydrogen phosphate (DHP) ...
3
votes
1answer
89 views

Figuring out the pH

So, I’m refreshing my college chemistry a bit. Could someone give me a pointer on the following practice exercise? What is the pH at 25 degrees Celsius in a bucket with 10 liter pure water in which a ...
3
votes
1answer
52 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: $K_h = 5.6\times 10^{-10}$ ...
3
votes
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? ...
3
votes
1answer
66 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 ...
3
votes
1answer
115 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 ...
3
votes
1answer
118 views

Why isn't there a third buffering zone in the pH curve of this titration?

I'm in chem 30 right now and we were learning about pH curves and buffering zones. I was looking at a question on the titration of $\ce{H3PO4}$ with $\ce{NaOH}$. The curve showed two qualitative ...
3
votes
1answer
378 views

How would one correct for a blank in a potentiometric titration?

I want to do a potentiometric titration with perchloric acid of a sample consisting of active drug (weak base) and two other components. Based on theory, I already know that these two other components ...
3
votes
2answers
1k views

Can hydrofluoric acid etch glass at a pH of 7.0?

Will it still etch glass when very dilute? Will the reaction still proceed slowly? At what pH will the reaction stop completely? From Wikipedia on hydrogen fluoride: "Although hydrofluoric acid is ...
3
votes
3answers
2k views

Solubility Product and Buffers

I've been assigned a homework and the question looks like this :- The ionization constant of benzoic acid is $6.46 \times 10^{-5}$ and solubility product for silver benzoate is $2.5 \times 10^{-13}$...
3
votes
2answers
10k views

Diluting acetic acid to obtain a solution of pH 5 [closed]

What percent of a solution needs to be acetic acid for a particular $\mathrm{pH}$? I have 100% acetic acid, and want $1~\mathrm{L}$ of solution with a $\mathrm{pH}$ of 5. I've done some research, but ...
3
votes
2answers
1k views

Carbonic acid-hydrogencarbonate buffer system pH calculation?

I am learning about the pH of buffer solutions, and am slightly confused by my text book's calculation. For the blood's buffer system of carbonic acid and hydrogencarbonate ions as the conjugate case, ...
3
votes
2answers
656 views

How to report pH values?

I have measured the pH in the water-soluble fraction of a powder. I weighed in a certain amount of powder and a certain amount of water, and extracted the water-soluble fraction. I then measured the ...
3
votes
1answer
740 views

How do I know that an acid and conjugate base are present in equimolar amounts?

Acetylsalicylic acid is a molecule in several popular drugs such as Magnyl and aspirin. Its pKa is 3.5, and I'm about to calculate the pH of a 0.010 M solution of acetylsalicylic acid. I've read up ...
3
votes
1answer
163 views

Carbonate + acid reactions - How to recognize these type of reactions?

So I've got $$\ce{CaCO_3 + HCl \rightarrow CO_2 + H_2 O + CaCl_2}$$ I'm wondering how I can recognize these types of reactions? I know that when I mix an acid and a base I get salt and water but in ...
3
votes
2answers
148 views

Why does the pH of this solution rise instead of fall when exposed to the atmosphere?

I have a couple of big barrels with a $50\,\mathrm{L}$ demi-water solution of the following nutrients: $$ \begin{array}{rl} 200~\mathrm{\mu M} & \ce{NH4NO3} & +\\ 30~\mathrm{\mu M} & \ce{...
3
votes
1answer
346 views

Amphoteric amino acid titration

Glycine $(\ce{NH2CH2COOH})$ is an amino acid with two $\mathrm{p}K_a$ values $(\mathrm{p}K_{a,1}=2.0, \ \ce{COOH};\ \mathrm{p}K_{a,2}=10.0, \ \ce{NH2})$. (a) If $0.01~\mathrm{mol}$ of this amino ...
3
votes
1answer
123 views

Less maintenance-dependent continuous pH testing

I am creating an automated chemical component mixing system (DIY project). One of the features required is continuous monitoring of pH value in my main solution. I do not need it to be very precise, ...
3
votes
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 ...
3
votes
1answer
1k 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 $\ce{NH4HSO4}$ ...
3
votes
1answer
113 views

Which formula to use to find the pH of a solution? [closed]

I just had my first exam yesterday, and I'm always tripped with this question that combines neutralization with buffer solution. The task is to find the pH. I did try to understand the general concept ...
3
votes
1answer
1k views

Does gold always become gold chloride when dissolved with HCl and an oxidizer and can it always be precipitated with sodium metabisulfate?

I tried to extract gold from computer parts by STRIPPING the gold using $\ce{HCl}$ and $\ce{H2O2}$ by dissolving the copper & nickel underneath but i added FAR too much $\ce{H2O2}$ by a stupid ...
3
votes
3answers
203 views

Acid disassociation constant of an acid when pH of a solution is given

Q. A solution contains $\pu{0.09M}~\ce{HCl}, \pu{0.09M}~\ce{CHCl2COOH}$ and $\pu{0.1M}~\ce{CH3COOH}$. The pH of the solution is 1. If $\ce{K_a}$ for acetic acid is $10^{-5}$, then calculate $\ce{K_a}$ ...
3
votes
1answer
1k views

Can the colour change in litmus paper be explained by conjugated systems?

I have been trying to understand the colour change in litmus paper on a more detailed level than "the chemical identity changes, and therefore also physical properties". I have knowledge of the ...
3
votes
1answer
145 views

Is there any reason to fear personal exposure to rain with a pH of 3.1?

Where I live now there can be significantly acidic rain. The government posts measurements for many cities and there can be stretches for days or longer with reported pH of 3.2 or 3.1. I even saw 2.9 ...

1 2 3 4 5 14