Question

In: Chemistry

You work in a medical research lab with a biochemist who asks you to make a...

You work in a medical research lab with a biochemist who asks you to make a 1.00 L phosphate buffer stock solution with pH = 7.4. The total phosphorus concentration is to be 0.250 M. In the storeroom, there are the following reagents: (1) a 3.00 M phosphoric acid stock solution, (2) solid sodium dihydrogen phosphate, (3) solid sodium monohydrogen phosphate, (4) solid, sodium phosphate, (5) a 3.00 M HCl(aq) stock solution, (6) a 3.00 M NaOH(aq) stock solution, and (7) deionized water.

(i) (2 pts) To make an optimum buffer, it is important that the pKa of the acid part is close to the target pH of the buffer. Which phosphate species has a pKa value closest to pH = 7.4?

(ii) (4 pts) Choose this phosphate species (in i) as the only phosphorus component. What amounts of this substance and any other reagents (grams of solid(s); mL of any solution(s) and water) would you need to make the buffer with pH = 7.4?

(iii)(4 pts) Choose this phosphate species (in i) and either its conjugate acid or base as the only two phosphorus components. What amounts of this substance, its conjugate acid or base, and water (grams of solid(s); mL of any solution(s) and water) would you need to make the buffer with pH = 7.4?

Solutions

Expert Solution

Using Hendersen-Hasselbalck equation,

pH = pKa + log([base]/[acid])

pKa2 for H3PO4 = 7.2

7.4 = 7.2 + log([base]/[acid])

[base] = 1.585[acid]

[acid] + [base] = 0.25

[base] = 0.25 - [acid]

0.25 - [acid] = 1.585[acid]

[acid] = 0.097 M

[base] = 0.153 M

(i) H2PO4- has a pKa of 7.2. that is pKa2 for H3PO4 is close to desired pH

(ii) [H2PO4-] = 0.097 M

moles of NaH2PO4 = molarity x volume = 0.097 x 1 = 0.097 M

so grams of NaH2PO4 required = 0.097 x 119.98 = 11.64 g

[HPO4^2-] = 0.153 M

moles of HPO4^2- = 0.153 mols

grams of Na2HPO4 required = 0.153 x 141.96 = 21.72 g

So we would require, 11.64 g of NaHPO4 in 1 L of water to give a buffer with pH 7.4

(iii) Conjugate base of H2PO4- is HPO4^2-

[HPO4^2-] = 0.153 M

moles of HPO4^2- = 0.153 mols

grams of Na2HPO4 required = 0.153 x 141.96 = 21.72 g

So we would require, 21.73 g of Na2HPO4 in 1 L of water to give a buffer with pH 7.4

The two salts are put in 1 L of water to give a buffer of pH 7.4. Total volume is 1 L.


Related Solutions

Library Research Project 

Research an actual Medical Malpractice Case. Then make a 750 words paper that...
Library Research Project 

Research an actual Medical Malpractice Case. Then make a 750 words paper that includes the following components: A. An introduction and description of the case. 
B. Evidence of laws that may have been broken.
C. Evidence of ethics that may not have been followed. 
D. Evidence of negligence. 
E. Evidence of HIPAA violations.
F. Conclude your thoughts and opinions as to the guilt or innocence of the Health Care professional. Formulate your theory as to why it...
Imagine you are on a work team that has two people who make all the decisions....
Imagine you are on a work team that has two people who make all the decisions. These two people tend to work closely together and ignore your input during meetings. Two other team members have stopped contributing to the team and sometimes don’t even attend meetings. The team has been together for over three months now. Your supervisor wants you to talk with the entire team about how all of you can function together and work more effectively as a...
You work on a medical/surgical floor at a county medical center. There is a patient on...
You work on a medical/surgical floor at a county medical center. There is a patient on your floor who had a stroke, and his wife is his power of attorney. The patient’s stroke was mild and his cognitive functions were not affected by the stroke (he is oriented times 3). He has been on the unit for 3 weeks. Early in his hospitalization his hemoglobin was found to be 6.0g. The patient’s wife is a Jehovah’s Witness; however, the patient...
Your lab manager asks you to create the new control range for the new lot of...
Your lab manager asks you to create the new control range for the new lot of hematology control level 1. The following 10 hemoglobin values are gathered to determine the control limits. Using a calculator or website SD function, calculate and record the mean, the standard deviation, and the 95% confidence interval for this set of values. (3 pts) 4.2, 4.7, 4.3, 4.4, 4.6, 4.7, 4.9, 5.0, 4.6, 4.0, Mean:____4.54______ 1 SD:__0.2963______ 95% Confidence range (2 SD range):_____1.96___________
Imagine that you work in a medical facility the provides medical laboratory/pathology and medical Imaging services....
Imagine that you work in a medical facility the provides medical laboratory/pathology and medical Imaging services. In computerising this facility to share collected patient information with other facilities, what standards are likely to be used? Your answer should provide an explanation of why and how these standards would be used. Try to limit your answer to 300 words.
You have two hourly contract employees who work for you. They both make $30 per hour....
You have two hourly contract employees who work for you. They both make $30 per hour. How much should you budget in labour costs for the year, based on the following assumptions; (i) Total working hours in a year (40 hours per week x 52 weeks) (ii) 10 holidays per year (8 hours per day) that you do not pay them for (iii) 10 days vacation per year (8 hours per day) that you do not pay them for (iv)...
Imagine the CEO of a software house asks you to make a system that automates the...
Imagine the CEO of a software house asks you to make a system that automates the SDLC process. Based on the initial requirements, you were successfully able to make a prototype that captures almost 40$-50% functionalities. You presented the demo to the CEO and now CEO is very impressed with the work. The CEO has ordered you to add some new features in the prototype and release the product as soon as possible. Being the lead developer of the project,...
Que: This question asks you to demonstrate an understanding of the work of Karl Marx as...
Que: This question asks you to demonstrate an understanding of the work of Karl Marx as covered You are to take the side of the proletariat and argue the reason(s) why a fast-food worker SHOULD be paid $15.00 per hour and You are to take the side of the bourgeoisie and argue the reason(s) why a fast food worker SHOULD NOT be paid $15.00 per hour. (The Answer need to be in soft copy only)
Treatment Centers/Medical Research for Asthma (5 pts) Who/What/Where of areas/places that are doing research for this...
Treatment Centers/Medical Research for Asthma (5 pts) Who/What/Where of areas/places that are doing research for this particular disease. What are some of the medical research facilities currently doing research on this disease AND/OR what are some treatment centers for the disease/disorder.
1. You work on a FX trading desk. A client calls and asks you the deposit...
1. You work on a FX trading desk. A client calls and asks you the deposit rate you can guarantee them in the Malaysian Ringgit (MYR) currency for one year. You have the below information. What deposit rate can you offer the client as a guarantee you can secure them? Your main funding currency is USD. Answer in percentage points to the fourth decimal (e.g. 2.5000% is 2.5000). USD/MYR Spot:    4.1090 USD/MYR 1-yr Forward FX: 4.1695 USD 1yr Interest...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT