Questions tagged [buffer]
Use for questions regarding solutions containing a mixture of a strong acid and weak base or vice versa.
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questions
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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 ...
0
votes
1answer
35 views
pH of PBS after adding acetic acid
Why is there a need for pH adjustment below ? Can pH go below 4.3 after adding acetic acid to PBS ?
“First prepare stock solution consisting of 50 ml of 10× PBS (pH 7.4), 12.5 ml of 80% glycerol, and ...
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0answers
34 views
Calcium reactor and pH
In a $400$ liter aquarium, whose bicarbonate level is kept constant, it is initially equal to $122\space\text{mg/L}$ and you want to raise the $\text{pH}$ from $8.3$ to $8.48$. For this, a calcium ...
-1
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1answer
38 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 ...
-1
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1answer
39 views
How do buffers work? and why only solutions of a weak acid and its salt with a strong base or vice versa work as a buffer [closed]
Please note that the definition of a buffer in my textbook is given as
The solutions which resist change in pH on dilution or with the addition of small amounts of acid and alkali are called Buffer ...
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32 views
How do two species from the same buffer system have different pKa values? [closed]
$$
\begin{array}{lr}
\hline
\text{Reagent}~(\pu{0.1 M}~\text{solutions}) & \mathrm{p}K_\mathrm{a} \\
\hline
\text{Ammonia} & 9.25 \\
\text{Acetic acid} & 4.75 \\
\text{Ammonium chloride} &...
-1
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1answer
59 views
How exactly does a buffer made up of a weak acid and its conjugate base work upon addition of hydroxide ions? [duplicate]
Consider a buffer solution containing a weak acid and its conjugate base ($c_\mathrm{total} = \pu{0.1 mol L-1}$):
$$\ce{HA <=> H^+ + A^-}$$
When $\ce{H+}$ ions are added (from a strong acid), ...
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1answer
29 views
buffer "recipe" needed [closed]
I have a question, that I hope can be answered without the respondant showing off how much they know about chemistry and talking in "words of art". It's been 50 years since I tool chemistry ...
1
vote
0answers
53 views
Buffer problem in polyprotic acids [duplicate]
I read a problem which was as follows:
Equal volumes of $\pu{1M} \ \ce{H3PO4}$ and $\pu{1M} \ \ce{Na3PO4}$ are mixed. The $\mathrm{pH}$ of the resultant mixture is (along with this $K_\mathrm{a1}, K_\...
2
votes
2answers
106 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}$ ...
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0answers
35 views
Preparation of phosphate buffer of ph 7.4
Can I make a phosphate buffer of pH 7.4 starting with phosphoric acid and then adding NaOH until the pH reaches 7.4. What are the disadvantages of using this method over sodium phosphates?
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1answer
32 views
titrating a weak acid with strong base in the present of buffer
I would like to get a neutral salt solution for a weak acid whose pKa is 3.42. This weak acid is in the form of solution (now is 20% w/w), thus I cannot directly dissolve the powder into the buffer ...
0
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0answers
34 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{...
0
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2answers
99 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 ...
9
votes
2answers
367 views
How to (numerically) model a phosphoric acid titration curve
I've been learning how to simulate a 1M phosphoric acid titration curve using numerical methods in R.
So far has this has been the best curve:
Notice how it flattens out (artificially) towards the ...
-2
votes
1answer
265 views
Is mixture of ammonium hydroxide and ammonium nitrate a buffer solution? [closed]
Is a mixture of $\ce{NH4OH}$ and $\ce{NH4NO3}$ a buffer solution?
I have seen some examples with $\ce{NH4OH}$ and $\ce{NH4Cl}$ but never $\ce{NH4NO3}$.
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1answer
57 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 ...
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1answer
100 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{...
-2
votes
1answer
495 views
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}$...
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0answers
136 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}$ ...
0
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1answer
54 views
Question regarding chemical equilibrium when adding a salt to acid solution
Having read the following was wondering something:
$$\mathrm {p}K_\mathrm{a} = -\log\frac{[\ce{H+}]_\mathrm{eq}[\ce{A-}]_\mathrm{eq}}{[\ce{HA}]_\mathrm{eq}} $$
$$\ce{HA <=> H+ + A-}$$
$$\mathrm{...
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vote
2answers
78 views
Confusion regarding the mechanism of acidic/basic buffer solutions
While learning about acidic and basic buffer solutions we were told that they can resist pH change if we add small amounts of acid or base by neutralizing the $\ce{H+}$/$\ce{OH-}$ ions from the added ...
3
votes
1answer
690 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, ...
2
votes
1answer
198 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 $\mathrm{pH}$ ...
0
votes
1answer
509 views
How to change pH of CuSO4?
I'm currently very desperate to know this. I'm doing an experiment about adsorption/chelation of Cu ions in CuSO4 using banana peels using the UV-Visible spectroscopy. How do I change the pH of 0.1M ...
-2
votes
2answers
243 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 ...
-1
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1answer
75 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 ...
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0answers
385 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 ...
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2answers
4k views
Calculating ratio of conjugate base and acid when pH and pKa are given
Buffer solutions are used by biological mammalian systems to maintain the $\mathrm{pH}$ of blood plasma within a narrow range. In these systems, the compound from which this solution is obtained is $\...
2
votes
1answer
88 views
Finding new pH after adding potassium hydroxide to citrate buffer
Calculate the $\mathrm{pH}$ change of citrate buffer containing $\pu{10.26 mmol}$ of citric acid and $\pu{6.98 mmol}$ citrate caused by adding $\pu{4.72 mmol}$ of potassium hydroxide. $\mathrm{p}K_\...
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1answer
2k views
How to calculate bicarbonate and carbonate from total alkalinity [closed]
It's been a long time since I did my chemistry classes and I'm currently trying to analyze groundwater samples for hydrogeology purposes. I would like to evaluate carbonate and bicarbonate ...
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2answers
57 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 $0.2\textrm{M } \ce{NaOH}/\ce{HCl}$. ...
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0answers
65 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....
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3answers
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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 ...
1
vote
1answer
41 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 ...
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0answers
322 views
Stable physiological buffer to make NAD+ solution
I was wondering what would be the most stable physiological buffer for nicotinamide adenine dinucleotide (NAD+), for potential storage as frozen aliquots - 6 months stability or around there would be ...
0
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0answers
49 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 &...
2
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2answers
397 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 ...
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votes
1answer
63 views
Preparation of Ca/PO4/acetate solution
EDIT: This is not a homework problem and we need this for an exploratory study on teeth demineralization. There is further work planned around this activity, which may not be relevant to the question. ...
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3answers
4k views
What's the effect of temperature on buffering capacity?
I did some research online but I still couldn't get any conclusion. Some said that the buffering capacity decreases when temperature increases because of the increase in ionisation of the weak acid ...
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2answers
5k 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 $\...
2
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1answer
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 ...
6
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3answers
3k 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 $\...
3
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1answer
85 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
1answer
714 views
What is total concentration of buffer used in derivation of buffer capacity?
ChemBuddy — The buffer capacity provides the following:
$$\ce{HA <=> H+ + A-}$$
Total concentration of the buffer $c_\mathrm{buf}$ is given by
$$c_\mathrm{buf} = [\ce{HA}] + [\ce{A-}]\tag{19.3}$...
3
votes
3answers
7k 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 $\...
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1answer
4k views
How many moles NH4Cl must be added to NH3 to create buffer with pH=9?
How many moles of $\ce{NH4Cl}$ must be added to $\pu{2.0 L}$ of $\pu{0.10 M}$ $\ce{NH3}$ to form a buffer with $\mathrm{pH}=9$? Assume the addition does not change the volume of the solution ...
