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
2
votes
1answer
85 views

Buffer Systems and Ion Reaction

If we have a buffer solution as follows where HA is a weak acid and $\ce{A-}$ is its conjugate base, $\ce{HA + H2O<=>H3O+ + A-}$, do we ever consider $\ce{A- + H2O<=>HA + OH-}$? This is ...
6
votes
2answers
21k views

MgCl2 acidic or neutral in water?

I'm currently taking chemistry 12. On our test we were asked, when given a $0.1~\mathrm{M}$ solution of certain compounds whether the resulting solution when added to water would be acidic, basic, or ...
0
votes
1answer
313 views

link between acidity and [H3O+]

Suppose I have an aqueous solution (1) of $\ce{CH3COOH}$. The chemical species in the solution will be $\ce{H2O, H3O+, CH3COO-}$ and, since it's a weak acid, some $\ce{CH3COOH}$ will remain. Suppose ...
5
votes
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 ...
1
vote
0answers
29 views

Predictions about hydrolysis reactions [duplicate]

Predict whether these $1.0~\mathrm{M}$ solutions are acidic, basic, or neutral. Lets start with $\ce{CH3NH3+NO3-}$ How do I approach a problem such as this? I certainly do not know all the chemical ...
5
votes
3answers
2k views

Solubility Product and Buffers

The ionization constant of benzoic acid is $6.46 \times 10^{-5}$ and solubility product for silver benzoate is $2.5 \times 10^{-13}$. How many times silver benzoate is more soluble in a buffer of $\...
1
vote
1answer
511 views

pH of a mixture of base and an acid

I have the following question: Assume that you have two solutions. One of $50\ \mathrm{cm^3}$ $\ce{HCl}$ $\mathrm{pH} = 1.3$ and one of $150\ \mathrm{cm^3}$ $\ce{Ba(OH)2}$ $\mathrm{pH} = 12.3$. If we ...
2
votes
1answer
5k views

Titration curve of a diprotic acid with a strong base titrant

I have wonders regarding the titration curve of the titration of sulphuric acid, or any diprotic acid, with a strong base. I am aware of the fact that a diprotic acid is protolysed in two steps but, ...
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 ...
2
votes
2answers
1k views

pH level of fabric with regard to inhibiting fungal growth

Someone on another forum made the point that doing laundry with sodium hypochlorite (bleach) will kill any fungus such as athlete's foot fungus, but that after the fabric dries, the pH level of the ...
1
vote
1answer
1k views

Phosphate buffer system

Can anyone show me how to find the masses of $\ce{NaH2PO4}$ and $\ce{Na2HPO4}$ needed to prepare $1.0~\mathrm{L}$ of a $0.1~\mathrm{M}$ phosphate buffer solution with $\mathrm{pH} = 7.4$ using the ...
12
votes
1answer
15k 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 ...
4
votes
3answers
635 views

What is the physical quantity/magnitude of pH?

I have a database to classify variables/parameters in water resources as follows: Variable: Precipitation (P); Quantity: Length; Units of measurement: mm (millimeters). Following the example, what ...
2
votes
0answers
638 views

Buffer capacity of different types of milk

Currently I am tasked with designing an experiment that that I will have to perform in 2-4 weeks, but I don't have to decide on on a topic soon. I was thinking of performing an acidometric titration (...
0
votes
0answers
384 views

Titration of hydrochloric acid with sodium hydroxide

I have a question regarding titration of hydrochloric acid with sodium hydroxide. Assume you have a solution of NaOH with pH = 12. With this NaOH you titrate a HCl solution. Then, will the pH of the ...
2
votes
0answers
36 views

Titration curve of strong acid with strong base [duplicate]

I have a question regarding the titration curve for $\ce{HCl}$ titrated with $\ce{NaOH}$. Why does it look like it does, with a steep slope near the equivalence point and a flat slope at the beginning ...
5
votes
1answer
5k views

Difference in calculated pH and the real pH of a phosphate buffer?

I'm from Colombia and I joined this site to ask a question that I could not solve yet. I am calculating the amounts to prepare a phosphate buffer with two salts. I want to prepare a buffer system with ...
2
votes
0answers
639 views

pH meter and paraformaldehyde

We have had an ongoing debate in our lab and several bad pH electrodes. I would like to ask the following question Do paraformaldehyde soloutions (2-4% w/v) damage pH meter electrodes? If so, why?
2
votes
1answer
590 views

pKa of Tris corrected for ionic strength

I have a question regarding the molar fraction calculation of Tris buffer at different temperatures. Tris dissociates according to the following equation: $$\ce{Tris + H2O -> Tris+ + OH-}$$ So, ...
2
votes
1answer
9k views

How to determine and derive the protonation state of a functional group based on its pKa?

In our biochemistry class we were introduced to a rule of thumb, which goes something like this: "If the pH of a solution is one or more units below the $\mathrm{p}K_\mathrm{a}$ of a group, then ...
1
vote
2answers
413 views

Wood Hydrolysis

According to this article on Live Strong, children have an average saliva pH of 7.5, while adults tend to be more acidic, with a saliva pH of 6.5 or lower. Even though a pH of 6 is not very ...
3
votes
2answers
15k 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?
1
vote
1answer
182 views

Calculating the pH

I have a question about a pH calculation which is the following: Calculate the pH of $10^{-8}\ \mathrm{mol/L}$ $\ce{HCl}$ solution in water. ($\ce{HCl}$ is a strong acid which completely ionizes in ...
1
vote
1answer
148 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 ...
2
votes
2answers
2k views

pH calculation - adding distilled water after titration [closed]

Will someone help me figure out how can I solve the following question? We are given 110 ml of acetic acid (pKa=4.76), with concentration of 1M, to which we add 10 ml of NaOH with concentration of ...
6
votes
1answer
139 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}}...
0
votes
1answer
980 views

pH of bleach solution slowly decreasing?

I work within a science department in a school. We are demonstrating Universal Indicator and something odd has happened. Our bleach solution (~2.5% Sodium hypochlorite) turns blue when UI is added but ...
3
votes
2answers
4k 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?
1
vote
1answer
5k views

p-value for ions in a solution?

The question in my class notes read as: Calculate the p-value for each ion in a solution that is $2.00 \times 10^{-7}\ \mathrm{M}$ in $\ce{NaCl}$ and $5.4 \times 10^{-4}\ \mathrm{M}$ in $\ce{HCl}$....
1
vote
2answers
370 views

Is there any law for pH conservation in chemical reactions?

I would like to know (just curiosity) if there is any law for pH conservation in chemical reactions. (like conservation of momentum in dynamics). EDIT The reaction I would like to take as example is ...
2
votes
1answer
73 views

Relative levels of the two most prominant glutamate species at pH 4.7

Calculate the relative levels (i.e. ratios of concentrations) of the two most prominant glutamate species at pH 4.7. I know that the Henderson–Hasselbalch equation is to be used which is $$\mathrm{pH=...
1
vote
2answers
22k views

Titration of H3PO4 with NaOH

I came across an ionic equilibrium problem stating: Find the pH when 150 ml 1 M $\ce{NaOH}$ has been added to 100 ml 1 M $\ce{H3PO4}$. I'm stuck with this question. What I know: $$\ce{H3PO4 + NaOH ...
5
votes
2answers
35k views

Does dissolving salt in water change the pH?

I am particularly interested in the effect or lack of effect of dissolved NaCl in regards to pH in water. It would be interesting also if anyone has any insight for other salts and their effects. ...
1
vote
0answers
551 views

Derivation of buffer capacity

I read an article about Buffer capacity The reaction is: $\ce{HA <=> H+ + A-}$ They have given that: But shouldn't $C_{buf}=[HA]+[A^-]+[H^+]$ ? The total concentration at equilibrium is $c(...
0
votes
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 ...
15
votes
1answer
6k views

Calculating the pH of a highly dilute solution of HCl

For relatively high concentrations of $\ce{HCl}$, I usually just assume that $[\ce{H+}] = [\ce{HCl}]$, because $\ce{HCl}$ is a strong acid and is completely ionized in solution. By taking the negative ...
2
votes
1answer
18k views

Calculating pH: Weak Acid, Strong Base

This is a question that had me puzzled for quite a while. I feel that information is missing. A weak acid, $\ce{HA}$, $K_a = 1.0$ x $10^{-4}$, is titrated with $\ce{NaOH}$. At the equivalence point,...
3
votes
2answers
28k 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\ \...
5
votes
2answers
7k views

Why is the pKa of the thiol group in N-acetylcysteine higher then the pKa of the thiol group in cysteine?

I understand why cysteine has a $\mathrm pK_{\mathrm a}$ of 8.3. But the $\mathrm pK_{\mathrm a}$ of thiol in N-acetylcysteine is 9.27. Since there is an acetyl group attached to the nitrogen, doesn't ...
3
votes
2answers
11k 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 ...
4
votes
1answer
2k views

pH of sodium metasilicate anhydrous vs pentahydrate when dissolved in water

I'm not a chemist and don't remember much chemistry from school, so please forgive a naive question (I've read the Wikipedia article on sodium silicate though). I'm researching this topic to make ...
5
votes
1answer
855 views

NaOH Normality Slowly Changing

Our lab uses a sodium hydroxide solution of a (theoretically) known normality (0.8000 - 1.0000) to titrate product samples for quality control. However, we suspect that the normality of the $\ce{NaOH}...
4
votes
1answer
4k views

Why does hydrogen phosphate act as a base?

Let's look at question c: a) Write a balanced equation for the reaction. $$\ce{2 NaOH + H3PO4 -> Na2HPO4 + 2 H2O (l)}$$ b) When some crystals of $\ce{Na2HPO4}$ were dissolved in water, ...
1
vote
0answers
161 views

Is the pH of a solution (orange juice) affected by the presence of a metal?

Is the pH of a solution (orange juice) affected by the presence of a metal (aluminium, tin or iron for example)? I know that the metal will corrode in the presence of an acid (citric acid in this case)...
4
votes
1answer
477 views

Atmospheric Nitrogen gas and human body pH buffers

It looks like the human body doesn't have the ability to breakdown atmospheric $\ce{N2}$, as of now $\ldots$ So an enzyme like nitrogenase (found in cyanobacteria) fixes $\ce{N2}$ and produces $\ce{...
7
votes
1answer
180 views

Amending soil pH to change the color of hydrangea flowers

I would like to ensure that my hydrangeas are blue. I am told that adding ammonium sulfate or aluminium sulfate will cause the soil to be more acidic. I am also told that adding elemental sulfur will ...
-3
votes
1answer
370 views

Ph of acid would be one? [closed]

I am interested in the chemical lsd or "acid". I wanted to know if lsd is acid in its pure form would that mean it is water?
3
votes
2answers
8k 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 ...
2
votes
1answer
4k views

Phosphate buffer from phosphoric acid and K2HPO4?

Is it possible to make a solution of ph 7 phosphate buffer solution using phosphoric acid and $\ce{K2HPO4}$ ? How can I calculate the amount of $\ce{K2HPO4}$ needed for 1L of phosphoric acid ? Edit: ...
7
votes
3answers
15k views

Why amino acids (Zwitterion) become either negative or positive at low and high pH solutions?

The amino acids are Zwitterions. In neutral pH, an Amino acid's amino group has a postive charge and Carboxyl group has negative charge. They cancel each others charge thanks to the $Hydrogen$ that's ...

1
9 10
11
12 13
15