What is Buffer: Definition and 198 Discussions

A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. In nature, there are many systems that use buffering for pH regulation. For example, the bicarbonate buffering system is used to regulate the pH of blood, and bicarbonate also acts as a buffer in the ocean.

View More On Wikipedia.org
Recent contents Top users
  1. D

    Interpreting buffer solution reaction

    So it seems I've been seeing two different ways of interpreting buffer solution reactions. One to me seems to work with Le Chatelier's Principle and the other doesn't. I am dropping a strong base, NaOH, into a weak acid/base buffer solution. View A: HA + H2O <--> (H3O+) + (A-) Reasoning: The...
  2. S

    Question about buffer solutions

    CH3COOH and CH3COONa is an acidic buffer. It retains the pH when acid is added as CH3COO-+H3O+ <==> CH3COOH+H2O. This reduces the amount of H3O+ allowing a smaller change in pH. It also increases the concentration of the CH3COOH. However, I was thinking about this other equation CH3COOH+OH-...
  3. J

    Finding Buffer Volume with Little Information

    Sorry. The title should read finding volume with little information. Humongous typo :) Homework Statement Suppose you are given 0.50 liter of 0.500 M acetic acid, and 0.50 liter of 0.250 liter sodium acetate. What is the maximum volume of buffer solution that you can make if the buffer must...
  4. J

    Writing Common Ion Concentration in Buffer Eq. Expression

    Homework Statement What is the pH of a buffer solution created by combining 100 mL of 0.2 M acetic acid and 400 mL of 0.10 M sodium acetate? Ka= 1.8 x 10^(-5)Homework Equations 1.8 x 10-5=([C2H3O2-][H+])/([HC2H3O2]) The Attempt at a Solution I know what I'm supposed to do to solve this...
  5. FeDeX_LaTeX

    Calculate pH of Buffer Solution & Understand Ka Equilibrium

    Homework Statement A student sets out to make a buffer solution. The student measures out 27 cm3 of 0.050 mol dm-3 HA solution and reacts with one-third of the volume of 0.10 mol dm-3 sodium hydroxide needed for complete neutralisation. (i) Calculate the volume of sodium hydroxide that the...
  6. S

    Why doesn't a weak acid/base act as a buffer on its own?

    Hello. I am a high school level student and I had a question about weak acids/bases and why they wouldn't work as a buffer on its own. If the dissociation of a weak acid is HA \rightleftharpoons H^{+} + A^{-}, then when we add OH^{-}, it will react with the H^{+} to form water. Because the...
  7. K

    Opamp - preceded by a unity buffer

    Homework Statement Hi, I'm trying to figure out the component values(Rf and C) for the circuit given. The circuit must be designed so that it has a cut-off frequency of 1khz and a low frequency magnitude gain of 1. I know how to do it if i ignore the unity buffer in front but I'm not sure how...
  8. D

    Buffer (pH of a weak acid decreases when we add NaOH Yes, really

    Buffer (pH of a weak acid decreases when we add NaOH! Yes, really.. This is not homework, but just something that I find not following general rule. Just wondering why. So We have the titration of 20.0 mL of .100M HF with .100M NaOH With 0mLof NaOH, the pH=2.08 (by calculating) But...
  9. P

    Can a 0.1M Buffer Solution Be Prepared Using Henderson-Hasselbalch Equation?

    Hey guys, This question seems pretty easy and straight forward but there's a nagging part of me that isn't sure. I want to say 'no' because I think that the solution goes back to it's acid constant dissociativity levels but I'm not sure. So the skinny is that someone needs to prepare a 0.1M...
  10. E

    Chemistry - desperately with buffer calculation.

    1. A buffer is prepared by mixing a 100.0ml of a 0.100M NH3 solution with a 0.200M solution of NH4Cl and making the total volume up to 1.000L of water. What is the volume of the NH4Cl solution required to achieve a buffer at pH=9.5 Ka of NH4+ = 5.6x10^-10 The textbook tell me that the...
  11. A

    Calculating Concentrations in a Buffer Solution

    Homework Statement [/b] A buffer solution was made using 50mL of 0.05M of ethanoic acid and 50mL 0.05 of sodium ethanoate. The question asks what is the concentration of ethanoic acid and ethanoate ions in the buffer solution. I assumed it would be 0.05M but when I asked for help I was told to...
  12. A

    High-Quality Output Buffer for Battery-Powered Audio Circuit | Impedance: 50Ω

    Hi guys, I'm currently designing a battery powered audio circuit. I've already finished all the signal processing stuff, and now I'm looking for a suitable output buffer to drive the speaker, which is about 50Ω impedance. Some of the requirements for the op amp buffer: - Single supply...
  13. Q

    Simple molarity, buffer question

    Homework Statement this is a part of a buffer solutions problem 3.3g of solid NaC2H3O2*3H2O added to 46mL of deionized water and 4.0 mL of 6.0M HC2H3O2. a. How many moles of HC2H3O2 are contained in a 19 mL of the above buffer? b. How many moles of NaOH would need to be added to the 19...
  14. mesa

    Question about acetic acid buffer solutions

    I want to make sure I understand the relationship between OH- and COOH properly. So if the NaOH is introduced into a buffer solution of acetic acid and it dissociates does the OH- (due to it's very electronegative nature) immediately rip off the H+ from the COOH? If I want to calculate pH do...
  15. T

    Solving Henderson-Hasselbalch Equation: Buffer Question

    BIOCHEM: buffer question! You have a sample of 50 mL of 0.2 M formic acid, which has a pKa of 3.75 (Ka = 1.78x10-4). How much 2 M KOH must be added to adjust the pH of the sample to 3.75? The correct answer is 2.5mL I tried using the henderson hasslebach equation and I just cannot wrap my...
  16. J

    Henderson-Hasselbalch buffer calculations - B + A Question

    Homework Statement To purify osprase you must use 750 mL of an extraction buffer consisting of 0.500 M Tris, pH 7.8, 100 mM NaCl, 20% sucrose. You have the following chemicals available: Tris base (FW = 121.1 g/mol; pKa = 8.1) 1.00 M HCl NaCl (FW = 58.4 g/mol) Sucrose (FW = 342 g/mol)...
  17. J

    Buffer Calculation using the Henderson-Hasselbalch Equation

    Homework Statement Prepare 750 mL of 0.5 M phosphate buffer, pH 6.7 and pKa 7.21. NaH2PO4 (119.96 g/mol) and Na2HPO4 (141.96 g/mol) is available to use. Homework Equations pH=pKa+log(B/A) The Attempt at a Solution I have the solution from my teacher, but I have no idea how he...
  18. Q

    Potassium Phosphate Buffer

    So I want to make a Potassium Phosphate Buffer from monobasic and dibasic forms of potassium phosphate because it was recommended for doing circular dichroism scans due to its low absorption in the UV region. However I don't understand the proportions of mono basic and dibasic forms of potassium...
  19. A

    Buffer solution capacity determination

    I have 3 buffer solutions with 3 components each and 3 buffer solutions with 2 components. I want to compare the capacities. But first I want to understand what exactlycapacity is and how can I calculate it! I have this page...
  20. E

    Finding the transfer Function of a Voltage Buffer

    This is the circuit that I'm trying to work with. Essentially, as far as I can see it's a voltage divider connected to a voltage follower. I have the output of the first op amp as: H(s)=S1/In1= 1/10 = 0.1. However I'm not sure if there are how to obtain characteristics of such a simple...
  21. S

    Calculating pH of a Buffer System After Addition of Base

    Homework Statement You have 400 mL of a solution of 0.20 M Na3PO4 buffer at pH 6.5. You add 0.7 g of NaOH to this solution. What will be the new pH? Homework Equations I suppose vital givens will be: pH = p_Ka + log[(A-)/(HA)] p_Ka values for H3PO4 = 2.15, 6.78, 12.4...
  22. M

    Preparation of sodium phosphate buffer solution

    hi guys, How can I prepare 20 mM sodium phosphate buffer (pH 6.9) containing 10 mM NaCl ? I mean how many grams of sodium dihydrogenphosphate, disodium hydrogenphosphate and sodium chloride are needed for 1 L of buffer solution. The buffer solution is prepared at room temperature (25C) and...
  23. M

    Mastering Buffer Solution Problems: A Guide for Understanding pH Changes

    I have a somewhat decent understanding of what a buffer is (stops an acid/base from changing the pH so dramatically), but when it comes to problems involving them, I am flat out lost and I haven't been so frustrated before. What is there to know about these types of questions, like what will the...
  24. B

    Find pH of Buffer: NaH2PO4 & Na2HPO4 Solution

    Homework Statement A buffer is made by dissolving 13.0g of sodium dihydrogen phosphate, NaH2PO4, and 15.0g of disodium hydrogen phosphate, Na2HPO4, in a litre of solution. What is the pH of the buffer? a) 7.84 b)7.47 c)7.20 d)6.85 e)6.63 Homework Equations pH = -log [H+]...
  25. M

    Quantity of buffer solution needed to resist pH change

    Hello there, I've got a question here which asks me to calculate how much (in mol/L) of buffer solution to add to 1 litre of solution to resist the change away from a pH of 7.0. a) if there was an increase of 3.99367 x 10-8 of [H+] ions Because the question is talking about pH in a...
  26. M

    Calculate pH of Media Buffer Solution

    I am trying to come up with a series of minimal media to grow a coculture. there are multiple compound concentrations being varied. I want to calculate the pH of each media. I am having a little bit of a problem calculating the final pH of each complex buffer. For example what would be the pH if...
  27. C

    How to make a sodium carbonate/sodium hydrogen carbonate buffer

    Homework Statement "Plan how to make 100mL of a buffer solution with a pH of 10.8 to be made using only sodium carbonate, sodium hydrogen carbonate and water" Homework Equations pH= pKa+ log(CO32-)/(HCO3-) The Attempt at a Solution I tried rearranging it, but I'm not sure what to do...
  28. M

    Calculating pH of buffer after adding HCl

    Homework Statement If the Tris buffer was exactly pH=9.0, calculate expected pH value after addition of 1 ml of 0.05 HCl. Buffer: 4 ml of 0.01M Tris, pH 9.0 HCl: 1 ml of 0.05M HCl Homework Equations H-H: pH=pKa+log[A-]/[HA] The Attempt at a Solution 9.0=8.21+log[A-]/[HA]...
  29. M

    Volume of Tris Needed to Prepare Buffer Solution

    Homework Statement Calculate the theoretical volumes of 1.0 M Tris base, 1.0 N HCL or 0.2 NaOH, and water needed to prepare 50 ml of a 0.1 M Tris buffer pH 9.0. pKa of Tris: 8.21 Homework Equations Henderson-Hasselbalch: pH=pKa + log[A-]/[HA]The Attempt at a Solution Honestly, I don't even know...
  30. K

    Adding a strong acid to buffer solution

    Homework Statement I'm trying to find the pH change of adding 0.001 mol of HNO_{}3 to a buffer solution containing 0.24 M HF and 0.55 M NaF in 0.100 L. K_{}a = 3.5E-4 therefore pK_{}a=3.47 Homework Equations pH=pK_{}a+log_{}10[base]/[acid] (Henderson-Hasselbach equation) and of...
  31. R

    Can strong acids and salts be used to create a pH 0.5 buffer?

    Homework Statement The assignment is to create a pH buffer in lab. My assignment is pH 0.5. Homework Equations [H+] = (Ka)([HA]/[A-]) log [HA] = pKa - pH + log [A-] The second equation was provided by the instructor, the first is from the textbook. The Attempt at a Solution...
  32. T

    Finding the pH of a buffer solution when a strong acid is added

    Homework Statement Three milliliters of a 2.0 M solution of HCL are added to 1 liter of buffer solution containing 0.40 moles of the weak acid, propanoic acid (Ka = 1.4 x 10-5) and .50 moles of its conjugate base, sodium propanate. 1) find the ph of the buffer solution 2) find the ph when...
  33. F

    Max Frequency of a 74AC240 Octal Buffer Chip

    I am trying to construct an inexpensive inverter for a battery-powered AC experiment. I was planning on using as part of it a 74AC240 buffer chip, however, no matter where I look I cannot seem to find what its maximum operating frequency is. The inverter needs to produce a frequency of several...
  34. S

    Preparing an extraction buffer with PMSF and 2-mercaptoethanol

    Homework Statement We have a 100 mL of 10 mM Tris-HCl, 1 mM EDTA, pH = 7.4 We're supposed to add PMSF to a final concentration of 1 mM and 2-mercaptoethanol to a final concentration of 1 mM. The stock solution of PMSF is .10 M PMSF in absolute ethanol. The 2-mercaptoethanol is also in the...
  35. S

    Chemistry Find number of moles of HCl to change pH of Histidine buffer.

    Homework Statement There is 400 mL of 0.2 M histidine buffer- pH 11. Find the moles of HCl that are needed to change the pH to 3.2. Homework Equations pH= pKa+log[b]/[a] The Attempt at a Solution First, this is how you would go from acid to base (acid-->base): 1. There is 400 mL of 0.2 M...
  36. J

    Buffer Solution Concentrations and Initial Conditions

    Homework Statement http://s359.photobucket.com/albums/oo40/jsmith613/?action=view&current=ChemistryQ.png I still don't see why they tell you the initial concentrations are the same? what if they were different? Homework Equations The Attempt at a Solution
  37. W

    Why does a buffer is used in an audio amplifier?

    Let a simple concept of an audio amplifier is to be designed like this (in BJT) : CC *CE* CE * OUTPUT ... and CC acts as a buffer. Why does a buffer is required for the amplification? Wouldn't it be much more simpler if CC is being canceled out? CC = Common Collector CE= Common Emitter...
  38. C

    Buffer Solutions: Explained with Equations

    what is buffer solution, explain with equation.
  39. C

    PKa and Buffer Solutions: Understanding Optimal pH for Maximum Buffer Capacity

    I read that a buffer solution has its greatest buffer capacity when its pH = pKa. The pH part I get but how can a solution have a pKa? Ka is the dissociation constant of an acid. Does this mean that to get maximum buffer capacity, you should adjust the pH of the solution so it equals the pKa of...
  40. V

    Efficient Buffer Preparation: 500ml MgCl2, Glucose, ATP, and Tris-Cl at pH 7.8

    Homework Statement Prepare 500ml of a reaction buffer containing .82% MgCl2, 62.5 mM glucose, 950 ATP, and 100mM Tris -Cl, pH 7.8 Use the stock solutions you have prepared we had to prepare in previous problems: 500ml 1.75M glucose 25mL 2.5% glucose 2L of 1.8 Tris, pH 8.5...
  41. V

    Question about sig figs in buffer problem

    Homework Statement prepare 1L of a .1M acetate buffer with a pH of 5.22 Homework Equations pK of acetate is 4.70 The Attempt at a Solution this is what my professor did: ph = pK + log(base/acid) 5.22 = 4.70 + log(base/acid) antilog(.52) = (base/acid) 3 = (acetate/acetic acid) = 3.3/1...
  42. A

    Citric acid buffer solution for prac

    Hi Guys, Citric acid has three different values for pKa because it is a polyprotic acid. I am aiming to make a buffer solution with sodium citrate but I am not sure which pKa value to use in the Henderson-Hasselbalch equation. Does anyone have any ideas?
  43. Z

    Designing a Unity Gain Common-Collector Buffer Using LT Spice | Tips & Tricks

    hi i am having my frist attempt on designing a common- collector transistor buffer which has a unity gain of 1. i am using lt spice to check the input and output of my buffer, however i am not sure how to determine if my buffer is working. if my input is a square wave with 3 volt amplitude...
  44. L

    Purpose of a voltage follower (buffer)?

    What are the applications of a voltage follower?
  45. X

    What is the pH of a buffer solution with known concentrations of HClO and NaClO?

    Homework Statement A 100.0mL buffer solution is 0.175M in HClO and 0.150M in NaClO. Find the pH of the solution.Homework Equations Ka=10^-pH ([H30+][A-])/([HA]) -log([H30+]) = pH The Attempt at a Solution [HClO] [H3O+] [ClO-] I .175 0 .150 C...
  46. K

    Calculating Concentrations in a 1.0-L Buffer Solution with Added HCl

    Homework Statement A 1.0-L buffer solution is 0.105 M in HNO2 and 0.180 M in NaNO3. Determine the concentrations of HNO2 and NaNO3 after addition of 1.8 g HCl. Homework Equations None The Attempt at a Solution I turned 1.8 g of HCl into mols and got 0.0494 mol of HCl. I subtracted...
  47. A

    Henderson-Hasselbalch and PH buffer equation

    Homework Statement Calculate the ph of a buffer made by mixing 50.0 mL of 0.10M of acetic acid with 50.0 mL of 0.10M sodium acetate. Use the Henderson-Hasselbalch equation. Homework Equations pH = pKa + log ([base]/[acid]) The Attempt at a Solution I know how to do this problem...
  48. R

    Buffer adding common ion effect?

    Homework Statement What will be the pH of a solution that contains 0.100 M CH3COOH and 0.100 M NaCH3COO?Ka = 1.8x10-5 IMPORTANT: THE REACTION IS NOT BETWEEN CH3COOH AND CH3COO- - My question here is why the ice table was setup as so by the instructor? see below... Homework...
  49. K

    Calculate the pH of a buffer made

    Homework Statement Calculate the pH of a buffer made with 10.0 g of K2HPO4 and 5.0 g of KH2PO4 in 1.0L of water. Homework Equations -log Ka + log (base/acid) = pH The Attempt at a Solution So...mathwise, I know how to do this problem. My only question is, aren't K2HPO4 and KH2PO4...
  50. U

    Henderson Hasselbach Eq'n. Tris HCL Buffer

    i need to create a solution of 0.70M Tris HCL buffer of pH 7.9 using 12.1 M of HCL pKa = 8.3 so far this is what i have: I need 8.49 g of Tris HCL because: ...(o.7M)*0.1L *(121.4g/mol) THIS part of the calculation is right so don't worry about it. however i can't get the ratios right...
Back
Top