All Questions
45 questions
0
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0
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27
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Calculating pH for Polyprotic Acids and Buffers
I’m trying to understand how to calculate pH for polyprotic acids in different scenarios, especially in relation to buffers, and I have a couple of questions:
When
pH≫pKa or pH≪pKa, should I calculate ...
- 1
-4
votes
1
answer
5k
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Salt hydrolysis or buffer solution [closed]
Whenever there a question comes to find the pH of the given solution, I always gets confused to identify the solution if it is a buffer solution or whether it will undergo salt hydrolysis .
Here is an ...
- 103
3
votes
0
answers
28
views
Non-binding buffer at pKa of roughly 6 that dissolves in ethanol?
I'm trying to find a proper buffer for my experiment, which I'd appreciate some suggestions on. I have a solution in which I want to measure the concentration of magnesium ions using a fluorescent ...
- 38.5k
-2
votes
3
answers
498
views
Why are buffer solutions not neutral
I am very confused about buffer solutions and I have lots of ideas about them which don’t integrate together so I really can’t tell which are correct and which are wrong. That being the case it’s ...
- 2,397
2
votes
1
answer
235
views
Effects when 100 mmol NaHCO3 are mixed with 50 mmol HCl
I read somewhere that when $\pu{100 mmol}\ \ce{NaHCO3}$ are mixed with $\pu{50 mmol}\ \ce{HCl}$, a buffer arises. I'm confused, since $\ce{HCl}$ is a strong acid, and I thought the classic buffer is ...
- 44.7k
2
votes
0
answers
112
views
Why do buffer solution only maintain pH to a certain limit?
I know that buffers have a capacity after which they are not able to maintain a relatively stable pH. This capacity is exceeded when we add too much acid or base but I was wondering why does this ...
- 4,636
2
votes
2
answers
74
views
Calculating the pH after adding hydrochloric acid to the potassium hydrogen phosphate solution
I am trying to calculate the $\mathrm{pH}$ of a solution obtained by mixing $\pu{20.00 mL}$ of $\pu{0.2 M}$ potassium hydrogen phosphate solution and $\pu{10.00 mL}$ of $\pu{0.25 M}$ hydrochloric acid ...
- 42.1k
-2
votes
1
answer
107
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Calculate the pH of a buffered solution after adding strong acid [closed]
Calculate the pH of a solution formed by the addition of $0.0020$ moles of $\ce{HCl}$ to $\pu{100.0 mL}$ of $\pu{0.200 M}$ $\ce{CH3NH2}$/ $\ce{0.100 M CH3NH3Cl}$.
$K_\mathrm{b}(\ce{CH3NH2})=4.4\times ...
- 42.3k
4
votes
1
answer
276
views
What is the math behind the formula for the concentration of the strong titrant when calculating theoretical buffer capacity of a diprotic system?
I have a question related to finding the theoretical buffer capacity of a diprotic system, specifically about the formula for the concentration of the strong titrant. In this post:
What is the formula ...
- 3,759
3
votes
1
answer
2k
views
Calculation of pH in diluted buffer
I have been preparing $\pu{150 mM}$ and $\pu{30 mM}$ Tris Buffers (pKa=8.3). Using .15 M solutions of both Tris and Tris-HCL.
Here is the information in which I have calculated theoretical pH values ...
CommunityBot
- 1
1
vote
0
answers
252
views
Exact calculation of pH of diprotic acid plus strong base
Another post has an excellent "exact" calculation for the [H+] (or pH) of a generic diprotic acid dissociating in water.
Combining acid dissociation constants to determine pH of diprotic ...
- 11
-1
votes
1
answer
162
views
pH and degree of dissociation of drugs
I have a doubt, i hope not so stupid.
Suppose we consider a buffer solution of acetic acid/acetate at pH = pKa = 4.76 and we add aspirin (pKa = 3.5): given that the pH of the solution is higher than ...
- 44.7k
-3
votes
1
answer
104
views
What is the charge of amino acid in alkaline conditions?
This problem refers to the protein buffer in a living system.
"If the blood pH becomes alkaline, there is a release of a proton from the
$\ce{NH3+}$ ion, which takes the $\ce{NH2}$ form."
I ...
- 42.3k
0
votes
0
answers
88
views
Does temperature affect ionic strength?
Hello I apologize if this is a dumb question but if I have a phosphate buffer made up of Na2HPO4 and NaH2PO4 and I gradually increase the temperature (lets say 10,20,30,40,50) what would happen to the ...
3
votes
0
answers
86
views
Measuring [A-]/[HA-] with Buffer and Indicator
I'm very confused on how to calculate the [A-]/[HA] value, given the fact that my dilution series uses buffers at various pH values with the same indicator (supplied at the same concentration to each ...
0
votes
1
answer
76
views
Why doesn't the volume of NH3 = 325 ml in this problem? [closed]
I'm struggling with the problem below, and don't understand why
A buffer solution with pH = 9.0 is to be prepared from a 0.2 M ammonia
solution and a 0.15 M $\ce{HCl}$ solution. The sum of the molar
...
- 423
0
votes
0
answers
81
views
How to calculate the buffer capacity for polyprotic acids? specifically H2PO4 --- HPO42- + H30+
as the title says. Is b= amount of OH-/ H3O divided by volume of buffer x change in pH wrong to use with polyprotic acids? Can I calculate the buffering capacity of a sodium phosphate buffer made up ...
- 11
0
votes
1
answer
1k
views
A method to create NH3-NH4Cl buffer solution using titration method
My aim is to create a basic buffer solution.
I know that to create a basic buffer solution, we need a strong acid and weak base. In my case I have chosen $\ce{NH3}$ and $\ce{NH4Cl}$.
Using titration, ...
- 42.1k
3
votes
2
answers
769
views
Finding final pH of the buffer solution without applying Henderson equation
A is beaker with $\pu{0.1 M}$ $\pu{25 cm^3}$ solution of $\ce{NH3}.$ B is beaker with $\pu{0.1 M}$ $\pu{5 cm^3}$ $\ce{HCl}.$ Now the solution of A and B is mixed. What will be the final $\mathrm{pH}$ ...
- 42.1k
-3
votes
1
answer
83
views
pH calculation of a mixure containing 2 strong acids and a buffer mixture
Calculate the pH of a mixtureof 10 mL 0,1 M HCl ; 5 mL 0,1 M HNO3 ; 10 mL 0,2 M HAc ; 15 mL 0,4 M NaAc.
My understanding was that I have to find the [H+] by:
finding the concentration of the products ...
- 42.3k
0
votes
0
answers
66
views
How to find pH for acetate buffer?
Calculate the pH of the solution that results when $\pu{40.0 mL}$ of $\pu{0.100 M}$ $\ce{CH3COOH}$ is mixed with $\pu{30.0 mL}$ of $\pu{0.200 M}$ $\ce{NaCH3COO}.$ $K_\mathrm{a}(\ce{CH3COOH}) = \pu{1....
- 38.5k
0
votes
0
answers
1k
views
How to calculate a citric acid and trisodium citrate buffer?
I am trying to calculate how to prepare 500 mL of a citric acid (H3Cit) and trisodium citrate (Na3Cit) buffer with a pH = 4.5 and a total concentration of 0.1 M. I know that it is necessary to use the ...
- 71
2
votes
2
answers
8k
views
Preparation of ammonium acetate buffer for HPLC
Buffer solutions are typically prepared by dissolving an appropriate salt in water and then adjusting the $\mathrm{pH}$ to the desired position by addition of the conjugate acid or base.
For example, ...
- 44.4k
1
vote
0
answers
611
views
How strongly affected is the buffering capacity of sodium carbonate - sodium bicarbonate by temperature changes?
I would like to do a lab regarding the affects of temperature on the buffering capacity of sodium carbonate - sodium bicarbonate in particular for sulfuric acid. Currently I have two competing ...
- 11
-1
votes
1
answer
803
views
Prepairing a Sodium Acetate buffer - Meaning of molarity
We have instructions to prepare a "50 mM Sodium Acetate, pH 5 solution". I am not entirely sure what does the molarity refer to in this case. Does it mean:
Add Sodium Acetate salt up to 50 ...
- 44.7k
1
vote
0
answers
98
views
How do two species from the same buffer system have different pKa values? [closed]
$$
\begin{array}{lr}
\hline
\text{Reagent}~(\pu{0.1 M}~\text{solutions}) & \mathrm{p}K_\mathrm{a} \\
\hline
\text{Ammonia} & 9.25 \\
\text{Acetic acid} & 4.75 \\
\text{Ammonium chloride} &...
- 38.5k
0
votes
1
answer
122
views
How exactly does a buffer made up of a weak acid and its conjugate base work upon addition of hydroxide ions? [duplicate]
Consider a buffer solution containing a weak acid and its conjugate base ($c_\mathrm{total} = \pu{0.1 mol L-1}$):
$$\ce{HA <=> H^+ + A^-}$$
When $\ce{H+}$ ions are added (from a strong acid), ...
- 42.3k
3
votes
2
answers
7k
views
How to Prepare a Buffer Solution?
Problem
I am given the task of preparing three buffer solutions at pH $10$, $9.5$, and $9.0$ . I have available concentrated ammonia and $\pu{3M}$ hydrochloric acid. The buffer capacity desired is $\...
- 42.3k
2
votes
2
answers
206
views
Finding the pOH of a buffer from the scratch without the Henderson Hasselbalch equation
I found this question on the internet that said:
Find the pOH of the solution obtained by mixing $\pu{0.1 mol}$ of $\mathrm{NH_4 OH}$ $(K_\mathrm b = 10^{-5})$ and $\pu{0.1 mol}$ of $\ce{(NH4)2SO4}$ ...
- 312
0
votes
0
answers
124
views
Given initial moles of weak acid, find moles of conjugate base to be added to get a final pH (volume unknown)
I am preparing notes on buffers and I came across this problem on a website:
Given 10.0 mmol of a weak acid HA with $\textrm{p}K_a =5$, how many mmol of NaA needs to be added to have a final $\textrm{...
- 1
0
votes
2
answers
835
views
Calculating the pH of a 'buffer' solution?
Question: Determine the $\mathrm{pH}$ of the solution resulting when $\pu{100 cm^3}$ of $\pu{0.50 mol dm-3}$ $\ce{CH2ClCOOH}$ is mixed with $\pu{200 cm^3}$ of $\pu{0.10 mol dm-3}$ $\ce{NaOH}$.
The ...
- 42.1k
5
votes
0
answers
190
views
What pH value of 1M sodium crotonate solution supposed to be?
I need to prepare the $\pu{1M}$ solution of sodium crotonate, however, I don't have one in lab, but I do have sodium hydroxide and crotonic acid.
Thus, I calculated that for $\pu{100 mL}$ of $\pu{1M}$ ...
- 151
-1
votes
1
answer
541
views
How to calculate how much weak acid would dissociate in water?
So I know water has a pH of 7. If we add 0.1 mol of a strong acid inside 1 liter of water, it WILL fully dissociate into 0.1 mol of A- and 0.1 mol of H+ thus making the pH of the solution 1.
But what ...
- 2,077
-4
votes
1
answer
792
views
How to calculate pH of an CH3COOH solution? [closed]
please, does anyone know, how to properly (with calculation procedure) calcutate $\mathrm{pH}$ of an $\ce{CH3COOH}$, when you know only:
-$\ce{CH3COOH}$ is 8% (water solution)
-density of $\ce{...
- 42.1k
-2
votes
1
answer
1k
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Preparation of a HCN/NaCN buffer that has a pH of 9.8 and an osmotic pressure of 1.35 atm at 298 K
You are asked to prepare $\pu{2.0 L}$ of a $\ce{HCN/NaCN}$ buffer that has a $\mathrm{pH}$ of $9.8$ and an osmotic pressure of $\pu{1.35 atm}$ at $\pu{298 K}$. What masses of $\ce{HCN}$ and $\ce{NaCN}$...
- 42.1k
-2
votes
2
answers
573
views
Why is sodium bicarbonate added to lower the pH? [closed]
I use salicylaldehyde, chloroacetic acid and sodium hydroxide for the synthesis of o-formylphenoxyacetic acid. In the procedure it is written that after the reaction I need to add sodium bicarbonate ...
- 44.7k
-1
votes
1
answer
280
views
When is a buffer solution considered efficient?
By this I mean what is the rigorous definition of a buffer solution?
I know that a buffer is a solution able to resist changes of $\mathrm{pH}$, but how much resistance to $\mathrm{pH}$ does a ...
- 44.7k
3
votes
3
answers
8k
views
Finding is the concentration of H⁺ in a benzoate buffer solution after adding HCl
Q: A buffer with a $\mathrm{pH}$ of 4.44 contains $\pu{0.21 M}$ of sodium benzoate and $\pu{0.12 M}$ of benzoic acid. What is the concentration of $\ce{[H+]}$ in the solution after the addition of $\...
- 42.1k
1
vote
0
answers
3k
views
Which is more effective at raising pH, Tums or baking soda?
Chemical buffers like Tums (calcium carbonate) and bases like baking soda (sodium bicarbonate) are both used medically to reduce acidity in the stomach to ease heartburn symptoms. I'm curious which is ...
-1
votes
2
answers
440
views
Creating a buffer with with a target pH and given weak base?
I need to create a $100\textrm{mL}$ buffer of $\textrm{pH = 9.20}$ with ammonia and ammonium chloride such that $\textrm{pH = }9.20\pm0.50$ with $20\textrm{mL}$ of $0.2\textrm{M } \ce{NaOH}/\ce{HCl}$. ...
- 22.4k
2
votes
0
answers
495
views
How to determine the pH of citrate buffer system
I used this table (http://microscopy.berkeley.edu/Resources/instruction/buffers.html) to make a citrate buffer system. The Pka value is 6.4, and I multiplied the solution by ten to make a larger batch....
- 5,080
5
votes
3
answers
3k
views
Am I understanding buffering capacity against strong acid/base correctly?
I just want to make sure I'm understanding buffering capacity correctly.
I've been working on this problem:
Suppose you have an acetic acid buffer, $\mathrm{p}K_\mathrm{a} = 4.74$, at the ...
- 44.7k
1
vote
1
answer
109
views
Why does Calcium (specifically Calcium Carbonate) inhibit the Citrate buffer system?
Is it because citrate chelates calcium and then is unable to react with other chemicals being added? If so can someone explain this reaction to me, or if not provide what the reason is? If anyone has ...
- 44.7k
2
votes
2
answers
2k
views
Can I make a buffer with a weak acid without adding it's conjugated base, when the desired pH of the solution is exactly the pKa of the weak acid?
An acid will be 50% dissociated when the solution it's in have a pH equal to the acid pKa ('afirmation 1', for later reference).
We also know that a good buffer solution have equal concentrations of ...
- 22.4k
0
votes
0
answers
52
views
Is contribution to pH by an acid or base always greater than salt hydrolysis?
I was solving a titration question and the reaction I came to was this:
$$
\begin{array}{lcccc}
\ce{&BOH(aq) &+ &HCl(aq) -> &BC(aq) &+ &H2O(l) }\\
\text{Initial} & x &...
- 30k