# Chemistry

PartA: What volume of 10.0M NaOH is needed to prepare a buffer with a pH of 7.79 using 31.52 g of TrisHCl? TrisHCl is a weak base and the molecular weight is 157.67 g/mol. I found the solution, it is 6.67 milliliters. The main question is:Part B: "The buffer from Part A is diluted to 1.00 L. To half of it (500.mL), you add 0.0150 mol of hydrogen ions without changing the volume. What is the resulting pH? pKb for the base= 5.91"

1. 👍 0
2. 👎 0
3. 👁 1,234
1. lol i m also looking for dis answer..
can u plz help me with
Methyl violet is an indicator that changes color over a range from PH = 0 to PH= 1.6. What is K(a) of methyl violet?

1. 👍 0
2. 👎 0
posted by julian
2. Here is how you came about the 6.67 mL.
pH = pKa + log (Base/acid)
If pKb = 5.91, then pKa = 8.09

7.79 = 8.09 + log(B/A)
base/acid = 0.501 or
base = 0.501(acid)

If we call the trisHCl, TH^+ and the base tris, just H, then
TH^+ + OH^- ==> H2O + T
If we start with 31.52/157.67 = 0.2 mol TH^, and call the NaOH added as y, then the final moles are
TH^+ = 0.2-y
T = y and we substitute into the above,
base = 0.501*(acid)
y moles base = 0.501(0.2-y)
y = 0.0667 moles which is 0.00667 L of 10 M NaOH or 6.67 mL.

Now we do the same kind of thing for the part B.
We have a mixture of T and TH^+.
We are adding H^+ to it.
T + H^+ ==> TH^+
We have 0.06676 moles T in the diluted solution. We are adding 0.150 moles H^+, so what are the final moles?
T = 0.006676 - 0.0150 = ??
TH^+ = 0.1332 + 0.0150 = ??
pH = pKa + log (base/acid)
Plug and chug. I get an answer approximately 7.5 pH but you need to go through it, watch the significant figures, and don't estimate as I did. Check my thinking. Check my work.

1. 👍 0
2. 👎 0
posted by DrBob222
3. I think I worked this last night.
Halfway between 0 and 1.6 is about pKa 0.8 so you can get Ka from that. Watch the significant figures. By the way, the pKa I found on the Internet was pKa = 0.8

1. 👍 0
2. 👎 0
posted by DrBob222
4. 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???

1. 👍 0
2. 👎 0
posted by Angie
5. it's 2.34 mL.
Find your number of moles from your ice chart, then use C = n/V, deviated to V = n/C x 1000mL = 2.34 mL

1. 👍 0
2. 👎 0
posted by Amy
6. i don't understand how you got the 0.501.. how do u get the base and the acid

1. 👍 0
2. 👎 0
7. the answer is 6.7 mL after using hints

1. 👍 0
2. 👎 0
8. Part C
What additional volume of 10.0 would be needed to exhaust the remaining capacity of the buffer after the reaction described in Part B?

1. 👍 0
2. 👎 0
posted by rita
9. for part B i got
pH = 5.91 + log (0.1632/0.008324) =6.75

1. 👍 0
2. 👎 0
posted by rita
10. Can anyone help me with

Part C
What additional volume of 10.0 would be needed to exhaust the remaining capacity of the buffer after the reaction described in Part B?

Thanks!

1. 👍 0
2. 👎 0
posted by Linda

0.34 ml

1. 👍 0
2. 👎 0
posted by hope
12. the answer for part C is not 0.34 mL by the way.

1. 👍 0
2. 👎 0
posted by Dr. E
13. Yeah, it is not 0.34, and i cant seem to find the right answer, did anyone find an answer that actually works? help would be greatly appreciated

1. 👍 0
2. 👎 0
posted by G
14. The answer is 1.34 mL

1. 👍 0
2. 👎 0
posted by Dr. E
15. for partc 1.34 is right!

1. 👍 0
2. 👎 0
16. the answer is not write!!!

1. 👍 0
2. 👎 0
17. for me I got 2.34 mL

1. 👍 0
2. 👎 0
posted by (:
18. it is the answer is not right...not the answer is not "write"

1. 👍 1
2. 👎 0
19. correct answer for C is 1.8

1. 👍 0
2. 👎 0
posted by NICK
20. 0.84ml is the correct answer
10M = 0.084 mol/ X L
Xml= 0.084 x1000/10 = 0.84

1. 👍 0
2. 👎 0
21. The correct answer is 1.8 mL

1. 👍 0
2. 👎 0
posted by Lina
22. The correct answer is 0.84mL.

1. 👍 0
2. 👎 0
23. In Mastering Chemistry none of those answers are right!

1. 👍 0
2. 👎 0
posted by April
24. Mastering Chem changes the individual numbers. Post work.

1. 👍 0
2. 👎 0
posted by Um
25. It is 0.34 ml trust me

1. 👍 0
2. 👎 0
posted by Rowena
26. the answer is 2.34 for part C. i got it right to yeh.

1. 👍 0
2. 👎 0
27. For Mastering Chem, its 0.34

1. 👍 0
2. 👎 0
posted by Ruth
28. both 0.34 and 0.84 are wrong

1. 👍 0
2. 👎 0
posted by mike

## Similar Questions

1. ### Chemistry

PartA: What volume of 10.0M NaOH is needed to prepare a buffer with a pH of 7.79 using 31.52 g of TrisHCl? TrisHCl is a weak base and the molecular weight is 157.67 g/mol. I found the solution, it is 6.67 milliliters. Part B: "The

asked by Linda on April 24, 2009
2. ### Chemistry

PartA: What volume of 10.0M NaOH is needed to prepare a buffer with a pH of 7.79 using 31.52 g of TrisHCl? TrisHCl is a weak base and the molecular weight is 157.67 g/mol. I found the solution, it is 6.67 milliliters. Part B: "The

asked by Fay on February 4, 2017
3. ### Chemistry

Q1: You wish to prepare a buffer solution with pH = 11.10. What volume of 6.0 M HCl would you add to 500 mL of 0.10 M (C2H5)2NH to prepare the buffer? You may assume that the solutionâ€™s volume remains constant. Q2: What is the

asked by Anonymous on February 24, 2013
4. ### Chemistry

Q1: You wish to prepare a buffer solution with pH = 11.10. What volume of 6.0 M HCl would you add to 500 mL of 0.10 M (C2H5)2NH to prepare the buffer? You may assume that the solutionâ€™s volume remains constant. Q2: What is the

asked by David on February 24, 2013
5. ### Chemistry

You have 800 mL of a 0.050M phosphate buffer, pH 6.5. You need to increase the pH of this buffer to 7.5 by using 6.00M NaOH. Determine the volume of NaOH needed. What will be the final concentration of the buffer?

asked by Izabella on September 25, 2013
6. ### Chem

Calculate the volume of .300 M NaOH needed to prepare a pH=3.50 buffer with 250ml of .075M HF solution. pKa (HF) = 3.15

asked by Will on February 11, 2012
7. ### chemistry

Prepare 500mL of a 0.200 M acetate buffer at pH 4.90 using only pure acetic acid, 3M NaOH, and water. 1) Add acetic acid to ~400mL of water in a 500 mL beaker. How many grams of acetic acid are needed? 2)Add 3 M NaOH solution

asked by Ryn on September 5, 2011
8. ### biology

You are preparing 500 mL of Denaturation Buffer containing 1.5 M NaCl and 0.5 M NaOH. Your stock solutions are 5 M NaCl and 6 M NaOH. How would you prepare the Denaturation Buffer? Include all of the solutions needed to make the

asked by sara on October 5, 2015
9. ### Quantitive Analysis

You are asked to prepare 500. mL of a 0.250 M acetate buffer at pH 4.90 using only pure acetic acid (MW=60.05 g/mol, pKa=4.76), 3.00 M NaOH, and water. Answer the following questions regarding the preparation of the buffer.

asked by Amanda Getto on October 18, 2015
10. ### Chemistry

In the study of biochemical processes, a common buffering agent is the weak base trishydroxymethylaminomethane, often abbreviated as Tris. At 25 C, Tris has a pKb of 5.91. The hydrochloride can be abbreviated as Tris HCl. What

asked by Alexandra on November 14, 2010

More Similar Questions