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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How to make MgCl2 buffer [closed]

I am told to make a MgCl2 buffer (50ml, 50mM, pH7.4). Could you let me know how to make this? (Including explanation and calculation) I understand when making Tris-HCL buffer, you could start with ...
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1 vote
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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 ...
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1 answer
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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 ...
-3 votes
1 answer
46 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 ...
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0 votes
0 answers
65 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 ...
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3 votes
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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
71 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 ...
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4 votes
2 answers
146 views

Why does "bis-tris propane" have two pKa values?

Wikipedia gives two pKa values for "Bis-tris propane". What about bis-tris-propane gives this compound two pKa values where other compounds have only one? How am I to choose which pKa value ...
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0 answers
34 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 ...
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33 views

Calculating acid volumes needed

I collect water quality samples used for irrigation. The samples are sent to a lab to measure $\ce{Ca^{2+}, Mg^{2+}, CO3^{2-}, HCO3^-}$, pH, and total dissolved solids. I need to use acid to prevent ...
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3 votes
1 answer
83 views

What happens when you add a weak acid to a solution buffered at a pH of 8.0?

There are a lot of textbook examples showing what happens to the pH of a buffered solution when you add strong acids and strong bases. Searching for an example calculation where you add weak acids or ...
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-1 votes
1 answer
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Will the solid formed after dehydration of a disodium hydrogen phosphate + sodium hydroxide solution be hygroscopic at STP?

Given a solution consisting of disodium hydrogen phosphate + sodium hydroxide (approaching a pH of 12), will the solid formed after dehydration of the solution be hygroscopic at STP? Which salts are ...
0 votes
1 answer
162 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, ...
-3 votes
1 answer
56 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 ...
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0 votes
0 answers
59 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....
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0 votes
2 answers
41 views

How to make NaxPO4 buffer?

I am currently trying to make a buffer for protein expression. According to the article, I am to use a buffer with $\pu{50 mM}$ $\ce{Na_{x}PO4}$, $\pu{pH 8}$ (and $\ce{0.5 M NaCl}$). How do I make the ...
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0 votes
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Finding dissolved amount of base from pH and solubility product

Calculate the amount of $\ce{Mg(OH)2}$ which is solubilized in $\pu{1.25 L}$ of a buffered solution at $\mathrm{pH} = 9.5$. $(K_\mathrm{sp}(\ce{Mg(OH)2}) = \pu{5.61E-12})$. From $\mathrm{pH}$ I ...
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0 votes
0 answers
340 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 ...
1 vote
0 answers
42 views

Can addition of a "neutral" salt like NaCl assist pH test strip measurement accuracy in low ionic strength/poorly buffered solutions?

After a web-search, it seems ISAs (Ionic Strength Adjusters) are offered commercially to assist pH electrode/probe measurements. Presumably meant to increase conductivity (without affecting pH ...
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How to estimate the pH of multi-component buffer (phosphate buffer in equilibrium with CO2 rich atmosphere)?

I wonder how the pH of buffer solution can be estimated if buffer consists of several systems in equilibrium to the gas phase. For example, (based on growth medium for one of the bacteria) buffer ...
1 vote
0 answers
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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
1 answer
369 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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1 answer
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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 ...
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-1 votes
1 answer
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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 ...
1 vote
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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} &...
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1 answer
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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), ...
-5 votes
1 answer
34 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
0 answers
55 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_\...
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2 votes
2 answers
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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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-1 votes
1 answer
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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 votes
0 answers
80 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{...
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2 answers
411 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 ...
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9 votes
2 answers
629 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 ...
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-2 votes
1 answer
804 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 $\ce{NH4NO3}$.
-1 votes
1 answer
275 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 ...
-4 votes
1 answer
362 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{...
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1 answer
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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 $\ce{NaCN}$...
5 votes
0 answers
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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 votes
1 answer
73 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{...
1 vote
2 answers
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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 ...
2 votes
2 answers
3k 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, ...
3 votes
2 answers
355 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 $\mathrm{pH}$ ...
-2 votes
1 answer
1k 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 ...
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-2 votes
2 answers
378 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 ...
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-1 votes
1 answer
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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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1 vote
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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 ...
0 votes
2 answers
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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 $\...
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2 votes
1 answer
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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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1 vote
1 answer
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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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2 answers
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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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