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13 Dec 2019

You wish to prepare 250. mL of a 0.300 M Tris buffer at room temperature (25 C) such that it has a pH of 7.80 at 10.0 C.
Starting with Tris base (F.W. 121.2, 99.9 % purity), answer the following questions regarding the preparation of this buffer. Refer to Table 2-1 in your coursepack for information regarding the temperature coefficient of Tris (∆pH/∆T).

-What mass of Tris is needed?

-To what pH (at room temperature, 25 C) would you adjust the buffer so that it had a pH of 7.80 at 10.0 C?

-Which would be the correct solution to use to adjust the pH?

-What volume of the 2 M solution identified above will be needed to reach the correct pH?

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Sixta Kovacek
Sixta KovacekLv2
17 Dec 2019

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Related questions

In the study of biochemical processes, a common buffering agent is the weak base trishydroxymethylaminomethane, (HOCH2)3CNH2, often abbreviated as Tris. At 25 ∘C, Tris has a pKb of 5.91.

The hydrochloride of Tris is (HOCH2)3CNH3Cl, which can be abbreviated as TrisHCl.

PART A

What volume of 10.0 M NaOH is needed to prepare a buffer with a pH of 7.79 using 31.52 g of TrisHCl?

Ans - 6.7mL.

PART B

The buffer from Part A is diluted to 1.00 L. To half of it (500. mL), you add 0.0100 mol of hydrogen ions without changing the volume. What is the pH of the final solution?

Ans - 7.58

PART C

What additional volume of 10.0 M HCl would be needed to exhaust the remaining capacity of the buffer after the reaction described in Part B? In other words, how much more of this HCl solution is required to consume the remaining Tris in the buffer?

Express your answer in milliliters using two significant figures.

NOTE: I NEED HELP WITH PART C. THE ANSWERS TO THE PRIOR PARTS WHERE PROVIDED BECAUSE THEY WOULD BE NEEDED IN SOLVING FOR PART C.

In the study of biochemical processes, a commonbuffering agent is the weak basetrishydroxymethylaminomethane,(HOCH2)3CNH2,often abbreviated as Tris. At 25 ?C, Tris has a pKb of5.91.

The hydrochloride of Tris is (HOCH2)3CNH3Cl, which can be abbreviated as TrisHCl.

What volume of 10.0 M NaOH is needed to prepare abuffer with a pHof 7.79 using 31.52 gof TrisHCl?

ANSWER: 6.7 mL



Question on this part:



The buffer from Part A is diluted to1.00 L. To half of it (500. mL), you add0.0300molof hydrogen ions without changing the volume.What is the pHof the final solution?

I know the answer for a) is B and for b) is D but I'm not sure why.. can someone show me the calculations?

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