Volume of Tris Needed to Prepare Buffer Solution

In summary: So the final equation would be 1.0M Tris+ (1.0N HCL)?In summary, to prepare a buffer with a pH of 9.0 using 0.1 M Tris and water, you would need: 0.005 mols of Tris, 1.0 M Tris base, and strong acid or strong base.
  • #1
MissSpice
4
0

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 how to start.

I know how to calculate moles of each, ratio of [Tris]/[Tris+] (I got 6.16 by 10^(9-8.21)), etc, but I don't what I actually need to use for the calculation... Help?
 
Physics news on Phys.org
  • #2
First of all - how much TRIS do you need to prepare 50 mL of 0.1 M solution?

Then you need to add strong acid (or strong base) to convert part of the TRIS to conjugate acid (or base) - this is a simple stoichiometry.

Finally you need to fill up to 50 mL.
 
  • #3
Borek said:
First of all - how much TRIS do you need to prepare 50 mL of 0.1 M solution?

I would need .005 mols, (0.1M Tris)x(0.05L)=.005. But then how do I go back to ml from here? And where does the 1.0M Tris base come in, since that is the solution I am diluting to get the 0.1M solution?

EDIT: I think I figured it out. Would it be (1.0M Tris)(X L)=(0.1M Tris)(.05L), so I would need 5mL of 1.0M Tris?

I still don't understand the HCl and NaOH part though; what do you mean by simple stoichiometry?
 
Last edited:
  • #4
MissSpice said:
Would it be (1.0M Tris)(X L)=(0.1M Tris)(.05L), so I would need 5mL of 1.0M Tris?

Yes, it is just an application of molar concentration definition (##C = \frac n V##) and mass conservation (amount of substance doesn't change during dilution).

I still don't understand the HCl and NaOH part though; what do you mean by simple stoichiometry?

First things first - for buffer solution you need a pair of conjugate acid and base. Is TRIS a base, or an acid? How can you prepare other substance from the pair?
 
  • #5
Borek said:
First things first - for buffer solution you need a pair of conjugate acid and base. Is TRIS a base, or an acid? How can you prepare other substance from the pair?

It's a base. So I would use the 1.0 N HCl to generate the acid, Tris+?
 
  • #6
TRISH+ to be exact, but yes, you are no the right track.

Assume protonation reaction went to completion - that's where the stoichiometry comes into play.
 

1. What is the formula for calculating the volume of tris needed to prepare a buffer solution?

The formula for calculating the volume of tris needed to prepare a buffer solution is V = (M * Vf * MWf) / MWi, where V is the volume of tris needed, M is the desired molarity of the buffer solution, Vf is the final volume of the buffer solution, MWf is the molecular weight of the final buffer solution, and MWi is the molecular weight of tris.

2. How do I determine the molarity of my buffer solution?

The molarity of a buffer solution can be determined by dividing the moles of the buffer component (such as tris) by the total volume of the solution in liters. Molarity = moles / volume (in liters).

3. Can I use any concentration of tris to prepare a buffer solution?

Yes, you can use any concentration of tris to prepare a buffer solution as long as you adjust the volume of tris needed according to the desired molarity of the buffer solution. However, it is recommended to use a concentration that is within the solubility range of the buffer component.

4. Why is it important to accurately measure the volume of tris for preparing a buffer solution?

Accurately measuring the volume of tris is important because it directly affects the molarity of the buffer solution. If the volume is not measured correctly, the final molarity of the buffer solution will be different from the desired molarity, which can affect the effectiveness of the buffer in maintaining the desired pH.

5. Can I use a different buffer component instead of tris to prepare a buffer solution?

Yes, you can use a different buffer component instead of tris to prepare a buffer solution. However, the formula for calculating the volume of the buffer component needed will be different and will depend on the specific buffer component and its molecular weight.

Similar threads

  • Biology and Chemistry Homework Help
Replies
3
Views
1K
  • Biology and Chemistry Homework Help
Replies
12
Views
2K
  • Biology and Chemistry Homework Help
Replies
1
Views
10K
  • Biology and Chemistry Homework Help
Replies
4
Views
1K
  • Biology and Chemistry Homework Help
Replies
5
Views
4K
Replies
4
Views
2K
  • Biology and Chemistry Homework Help
Replies
8
Views
3K
  • Biology and Chemistry Homework Help
Replies
1
Views
3K
  • Biology and Chemistry Homework Help
Replies
1
Views
3K
Replies
5
Views
7K
Back
Top