1) As a technician in a large pharmaceutical research firm, you need to produce
ID: 775462 • Letter: 1
Question
1) As a technician in a large pharmaceutical research firm, you need to produce 300.mL of 1.00 Mpotassium dihydrogen phosphate buffer solution of pH = 6.76. The pKa of H2PO4? is 7.21.
You have the following supplies: 2.00 L of 1.00 M KH2PO4 stock solution, 1.50 L of 1.00 M K2HPO4 stock solution, and a carboy of pure distilled H2O.
How much 1.00 M KH2PO4 will you need to make this solution?
2)
Carbon dioxide (CO2) and bicarbonate (HCO3?) concentrations in the bloodstream are physiologically controlled to keep blood pH constant at a normal value of 7.40.
Physicians use the following modified form of the Henderson-Hasselbalch equation to track changes in blood pH:
pH=pKa+log[HCO3?](0.030)(PCO2)
where [HCO3?] is given in millimoles/liter and the arterial blood partial pressure of CO2 is given in mmHg. The pKa of carbonic acid is 6.1. Hyperventilation causes a physiological state in which the concentration of CO2 in the bloodstream drops. The drop in the partial pressure of CO2 constricts arteries and reduces blood flow to the brain, causing dizziness or even fainting.
If the normal physiological concentration of HCO3? is 24 mM, what is the pH of blood if PCO2drops to 29.0mmHg ?
Explanation / Answer
Answer 1) Relevant equations
C(a) + C(b) = 100.0 mL
C(b) / C(a) = calculated ratio (0.85)
C(b) = C(a) x calculated ratio (0.85) C(a) + ( C(a) x (0.85) ) = 100.0 mL
C(a) = 100.0 / (1+(0.85)) mL 3.
The attempt at a solution I just for the life of me can't understand the section after the base/acid ratio is found. 7.14 = 7.21 + log [base]/[acid] 7.14 = 7.21 + log x logx = pH - pKa (-.07) x = 0.85 [base]/[acid] ratio
Answer:2 Message: As a technician in a large pharmaceutical research firm, you need to produce 150 m l of 1M potassium phosphate solution of pH = 7.02. The PKa of h2po4- is 7.21. You have 2L of 1M KH2PO4 solution and 1.5L of 1M K2HPO4solution, as well as a carboy of pure distilled H2O . How much 1 KH2PO4 will you need to make this solution?
The Henderson-Hasselbalch equation in medicine
Carbon dioxide ( ) and bicarbonate ( ) concentrations in the bloodstream are physiologically controlled to keep blood pH constant at a normal value of 7.4.
Physicians use the following modified form of the Henderson-Hasselbalch equation to track changes in blood pH:
PH=PKA +LOG [HCO3-]/[0.03] X[PCO2]
where HCO3- is given in millimoles/liter and the arterial blood partial pressure of CO2 is given in MMHG . The PKA of carbonic acid is 6.1. Hyperventilation causes a physiological state in which the concentration of CO2 in the bloodstream drops. The drop in the partial pressure of CO2 constricts arteries and reduces blood flow to the brain, causing dizziness or even fainting.
Part B
If the normal physiological concentration of HCO-3is 24mM , what is the pH of blood if PCO2 drops to 31.0?
Okay - Part A I'm just kind of guessing. You'll really need to get a proper chemistry guru for it. But here goes:
desired pH = 7.02
pKa = 7.21
pH = pKa - 0.19
10^(-0.19) = 0.645654...
[HA] / [A-] = 0.65
You will need to add volumes of KH2PO4 and K2HPO4 to make up the correct ratio of H2PO4- and HPO4--
x amount of K2HPO4 and (150-x) amount of KH2PO4 where (150-x) / x = 0.65
(150-x) = 0.65x
150 = 1.65x
x = 91mL of K2HPO4, 59mL of KH2PO4
Part B - This stuff I am more familiar with.
Using the Henderson Hasselbach equation
pH = 6.1 + log (24/(0.03x31))
pH = 7.51 (alkalosis)
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