Problems to do for phys pharm
5b. A physicians med order for 800mg of erythromycin to be added to 100ml of D5W for iv solution. What is the ph of the iv.. MW = 733.9 PKa = 8.88
C= .8g/733.9/.1L = .01 Ph = 7 + (1/2)(8.88+ log [.01])=10.5
5b. F you dissolve 201.5 mg of ephedrine HCl in 100mL water. What is th pH of the solution ? MW = 165.2 PKa = 9.6
C= 201.5/(165.2+36.5)/.1. .01M Ph = (1/2)(9.6- log 0.01) = 5.8
6a. Suppose you have 500 ml of sodium bicarbonate (NaHCO3) solution containing 420 mg NAHCO3 (MW= 84). If you add 265 mg sodium carbonate (NaCO3 MW= 106) to the solution, what is the pH of this solution ? For carbonic acid pKa1 = 6.37 and pKa2 = 10.33.
(0.420/84)/.5 = .01M (0.265/106)/.5= .005M PH= 10.33 + log(0.005/0.01) = 10.03
3. How much metoprolol is in one tablet of 100 mg Lopressor (MW= 267.4)(salt MW = 150.1) How much metoprolol succinate is in one tablet of 100 mg toprol xl (MW= 267.4)(salt MW = 118.1)
(267.4 x 2) + 150.1 / 267.4x2 = 1.28 100mg/1.28= 78.125 (267.4 x 2) + 118.1 / 267.4 x 2 = 1.22 78.125 x 1.22 = 95.16 mg
4a. A pharmacist needs prepare 200ml phenobarbital solution at the concentration of 0.02 M. How much in mg does the pharmacist need to weight. MW = 232.3
(X/232.3) / .2 = .02 X= 929mg
6b. Calculate the percentage of free acid for (a) phenobarbital (PKa= 7.4) and (b) hexobarbital (pka= 8.4) at physiological pH 7.4.
(a) log(A-/HA) = 7.4-7.4 = 0 Ratio of zero is 1 1/1+1 = 1/2 * 100% = 50% (b) log(A-/HA) = 7.4-8.4= -1 Ratio of -1 is (1/10) (1/1+0.1) = 1/1.1 *100% = 91%
4b. Which of the following statements is false 0.9% NaCl and 2% boric acid solutions are isosmotic to each other 0.9% NaCl and 2% boric acid solutions are both isotonic to the blood. An isotonic solution must be isosmotic to the blood An isosmotic solution may not be isotonic
0.9% NaCl and 2% boric acid solutions are both isotonic to the blood.
5a. The ph of a series of HCl solutions was determined by a ph meter. Why is the pH determined by the ph meter different from -log c? Why is the difference getting bigger at higher HCl concentration?
-Log c is the theoretical ph value and the ph determined by the meter is the actual value. The difference increases with increasing molar concentration and this more significant difference with concentration increase is due to ionic strength. -log c doesn't measure ionic strength it measures concentration while the ph meter measures actual ionic strength
2. If the oxygen concentration plasma is 0.053 mM what is the partial pressure of oxygen? Assuming Henry's constant is 1.39 x 10^-3 mM/mmHg and 1mmHg = 133.32 Pa.
0.053= (1.39x10^-3)p P= 38.13mmHg= 5083 Pa
4b. The freezing point of 0.10m acetic acid v=2 solution is -0.188*C(Kf = 1.86). What is the Van't Hoff factor? What would be the measured osmolality?
0.188/(1.86*0.1)= 1.01
2. Calculate the amount (in grams) of CO2 dissolved in 1.6 L of soda in the manufacturer uses 2.4 atm to carbonate the soda. The Henry's constant for CO2 is 0.034 mol/Latm
0.304(1.6)(2.4) = 0.13moles = 5.74 grams because the molecular weight is 44
4b. The freezing point of the blood from 20 normal subjects was measured and was average to -0.5712*C. What is the average milliosmolality of the blood Kf= 1.86
0.512/1.86= 0.307=307mOsmoles
4b. Dextrose is D-glucose. 5% dextrose solution (D5W) is isotonic. The molecular weight of dextrose is 180.16 and the density of D5W is 1.10. What is the Liso value for D5W?
0.52 as Tf is a known value 5/180.16 = 0.02775moles Liso = .52/.02775 = 1.9
4b. A solution containing 10.0 g sucrose dissolved in 100g of water has a boiling point of 100.149*C. What is the molecular weight of sucrose?
10g/100g 100.149-100= 0.149 is Tb m= 0.149/.51 = .292 m = wt/MW / kg = (10/MW)/.1 = .292 MW = 342.5
5b. Ascorbiic acd MW = 176.1 is a diprotic acid pKa1 = 4.10 and pKa2 = 11.80. What is the ph of solution when you dissolve 17.6g of ascorbic acid in 500 ml of water
17.6/176.1/0.5L = .199 Ph = (1/2)(4.1=log0.199)= 2.4
5a. What is more acidic PKa = 9 PKa = 2.5
2.5
5b. What is the ph of the solution when you dissolve 275mg phenytoin sodium in 100mL of water for injection? MW = 252.3 MW sodium = 23 PKa = 8.3
275/252+23/.1 = .01M Ph= 7+1.2x 8.3+log 0.01= 10.2
4b. If you need to prepare 300 mL of 1% procaine HCl (E= 0.21) solution. What is the volume of 0.9% NaCl solution that is needed to make the solution isotonic? If there is only 100mL 0.9% NaCl left in the pharmacy, but there is plenty of 5% dextrose solution, what is the volume of D5W solution should you use to make the procaine solution isotonic?
3*0.21*111.1= 69.99 300-69.99= 230ml Since 0.9% NaCl = D5W 230-100=130 ml D5W
Which dihydroxybenzoic acid has the highest solubility in water 2,6 3,5 2,3 2,5
3,5
4b. An injection solution contains 5.0g of ephedrine sulfate E= 0.23) in 500mL. What is the quantity of dextrose (E=0.16) that must be added to make the solution isotonic?
3.35 / 0.16 = 20.9
7. Which curve is for Indamoetacin Chlorpromazine Cefadroxil
7. Is there a limit to the solubility of the drug when you change the solution pH
6a. If you need to prepare a buffer solution with the desired pH at 5.25 which of the following acid or base would be selected: HPO4 (pKa1= 2.12) Formic acid (pKa= 3.75) Acetic acid (PKa= 4.75) KH2PO4 (PKa= 7.21)
Acetic acid
What is the ph of a 10 mM dipotassium phthalate solution (K2PT) PKa = 2.95 PKa2= 5.40
Because 3 ph units apart you can only use one pKA which should be step 2 PH = 7 + (1/2) (5.4+log 0.01) = 10.4
6a. What is the pH of 500 ml of a solution that contains 0.500 mol of acetate acid and 0.5 mole of sodium acetate? What is the solution pH when 10.0mL of 1.00 M NaOH solution is added? The pKa for acetic acid is 4.76.
Before= ph= PKa + log (base/acid) = 4.76 + log(.5/.5) = 4.76 After= ph = PKa +log (base/acid) = 4.76+ log (0.51/0.49) = 4.78 Acid + buffer = base .5 + 0.01 = .5 -.01 -.01. =+.01 .49 0. .51
4b. NaCl, KCl, CaCl2 and dextrose solutions have the same moral concentration (1.5m). You can predict that ________ solution would have the lowest freezing point and ____ solution would have the highest freezing point. NaCl and dextrose CaCl2 and NaCl NaCl and KCl CaCl2 and dextrose
CaCl2 and dextrose
7. A new drug is a weak base and is prepared in different salt forms (hydrochloride, sulfate, phosphate, etc.) the experiments show that different salts have different solubiloiy in water. This can be attributed to Different polymorphs Different dissociation rate Different ionic interactions Different solubility product constant (Ksp)
Different solubility product constant
3. If you need to prepare a solution of valproic acid a 100mg / 5 ml how much sodium valproate do you need to prepare 50ml such solution MW = 142.2
Fw sodium valproate = 142.2-1 + 23 = 164.2 Salt factor = 164.2/142.2 = 1.155 Wt salt = 100mg/5ml x 1.155 x 50ml = 1155 mg
5b. Which of the following is true The presence of the nitrogen atom in a drug molecule indicates that the drug is a weak base All weak acids have pka value below 7 All weak bases have pka value above 7 HCl does not have a pka value
HCl does not have a pka value
2. Which force is the weakest? Water Toluene Hexane Iodine and K+
Hexane
3. If patient asks you shy the Schaffer's brand has the highest potency how would you explain Molecular weight of hydrochloride acid is 36.5 Molecular weight of sulfuric acid is 98 Molecular weight of glucosamine is 179.2
Hydrochloride is the salt form HCl has a much lower MW More active ingredient in 1 tablet (2 x 179.2 + 98) / 2x179.2 = 1.27 100mg / 1.27 = 78.7 = 78.7% (178.2 + 36.5) / 179.2 = 1.2 100/ 1.2= 83 = 83%
6b. Clinical case: a depressed patient was admitted to the emergency room and was found to have consumed excessive amobarbital sodium tablets (pKa = 8) and the ph of the patients urine was found to be around 6. The clinical pharmacist recommend IV injection of sodium bicarbonate to increase the patients urine pH. Justify the use of this alkalizing agent in this emergency situation - note that the drug in the ionized form can be eliminated.
If a drug in ionized form can be eliminated you want more ionized. With a pH of 6 the drug is 99% unionized when the pH is increased more of the drug is ionized and able to be eliminated
5b. If you add 2 moles of NaCL to 0.1 M solution of acetic acid, the ph of the solution will —- when you measure the solution ph using a ph meter Increase Decrease Not change Fluctuate
Increase
1. Why do only certain drugs interact with certain targets in lock and key?
Intermolecular interactions
5b. What is the ph of 0.1 M H2SO4 solution Pka1 strong acid PKa 2 = 1.92
Ka = 10^-1.92 = 0.012 H = squareroot (0.012x0.1) = .0346 Ph = -log (.1+ 0.0346) = 0.87 ====hard problem may be come back to before exam
5b. Calculate the pH of a 0.01 M solution of ammonium acetate The acidictiy constant for acetic acid Ka = 1.75x10^-5 The basic it's constant for ammonium is KB= 1.74x10^-5
Ka1 = Kw / kB = 1*10^-14 /1.74x10^-5 = 5.75x106-10 Sqroot= (5.75x10^-10)(1.75x10^-5)= 1.00x10^-7 Ph = 7
6b. Diphenhydramine is a weak base with pka~9.0. What is the percentage of free base in the small intestines (ph=7)
Log(B/HB+) = 7-9= -2 Ratio of -2 is 1/100 (B/HB) = (1/100) B = HB*100 B/(B+HB*100) = 1/101 *100% = 0.99%
7. What is the solubility of benzylpenicillin G (pka= 2.76) at pH sufficiently low to allow only the nonionized form to be present? The solubility of the drug at pH 8 is 0.174 mol/L
Log(s-so/so)= ph -pka = 8-2.76= 5.24 (s-so/so) = (s/so - 1) = 10^5.24= 173780 (0.174/173780) = 1x10^-6
4a. What is the molar and molar concentration of 0.9% NaCl solution. Specific gravity = 1.0053 MW = 58.5 What is the moral concentration of 0.9% NaCl solution if 10g of KCl is added ?
Molar concentration = (wt/MW)/L = (.9/58.5) / .1L = .1538 M Molar concentration = (moles/ kg solvent) = (0.1538/.09963kg) = .1544m Wt soln = specific gravity x volume = (1.0053)(100mL) = 100.53g Wt solvent= 100.53-.9 = 99.63 g Will change molar concentration when you add solid it changes the volume of the solution but it wont change the molal because not adding solvent
4a. A buffer solution is prepared by using 0.3 moles of K2HPO4 and 0.1 mole of KH2PO4 in 0.5 l water. What is the ionic strength of this buffer solution
Molar concentration of K2HPO4 = (.3/.5) = .6M Molar concentration of KH2PO4 (.1/.5)= .2M Ion concentrations: K+ = 2x0.6 + 0.2 = 1.4M HPO4-2= 0.6 H2PO4- = .2M Ionic strength = (1.2) [(1.4 x 1^2) + (0.6 x .2^2) + (0.2 x -1^2)] = 2.0M
6b. The graph shows the amount of methamphetamine pKa= 9.9 excreted in acidic and alkaline fine over time. How do you explain the observed curve
More urine is excreted in acidic urine therefore you can conclude that most of the drug is in unionized form at pKa 9.9
The vapor pressure of CFC 11 and 12 is 13.4 and 84.9 psi respectively. If they are used as propellant as a 50:50 mixture (wt/wt) in an aerosol product. MW of CFC 11 and 12 is 137.4 and 120.9 g/mole respectively. What is the mole fraction for each component? What is the partial pressure of CFC 11 and 12? What is the total pressure?
N11= 50g/137.4= 0.364 moles N12=50g/120.9 = 0.414 moles 0.364+0.414= .778 P11= 13.4psi * (o.364/ 0.778) = 6.27 psi P12= 84.9 * (0.414/ 0.778) = 45.2 psi Total P = 6.27 + 45.2 psi = 51.47 psi
4a. A buffer consisting of 0.2 M sodium acetate and 0.3 M acetic acid. If the degree of dissolution of acetic acid (a) is 40% what is the ionic strength? Assuming complete dissolution of sodium acetate
Na concentration = .2 M Acetate = .2 + (.3x40% ) = .32 M Ionic strength = (1/2)(.2(1)^2 + (.32)(-1)^2 ) = .26M
4b. An injectable solution contains 5.0g of ephedrine sulfate (E=.23) in 500ml. What is the quantity of NaCl that must be added to make the solution isotonic?
NaCl equivalent = 5g*0.23= 1.15 NaCl needed = (0.9% * 500) - 1.15 = 3.35g
2. Gas has higher energy (enthalpy) but weaker intermolecular forces. Is this contradictory?
No, referring to different things KE because moving but intermolecular forces refer to potential interactions between molecules
2. At sea level the atmospheric pressure is 760 mmHg but drops to 400mmHg on the top of Mt. Everest. There is 21% oxygen in the air. What is the partial pressure of oxygen at the sea level and on the top of Mt. Everest? If there is about 0.04% CO2 in the air, what is the partial pressure of CO2?
O2 sea level= 760(.21)= 159.6 O2 mt= 400(.21) = 84 CO2 sea level = 760(.0004) = 0.304
4b. A sodium bicarbonate solution contains 0.030 g/ml of anhydrous sodium bicarbonate. The density of this solution is 1.0192 g/mL at 20*C and its measured osmolality is 614.9 mOsm/kg. What is milliosmolarity of this solution?
Osmolality = osmolality * (d-c) =(614.9)(1.0192-.03)= 608.3
4b. When you dissolve 171.2 grams of sucrose (MW 342.3) in 1000 g of water (MW 18). What is the percentage of water vapor pressure lowering at room temperature?
P= PaXb Mole fraction of sucrose M= 0.5 moles sucrose / 1kg = .5 P/p* = 0.018*m = .9%
5b. What is the pH of 0.01 M of procaine solution pka = 8.85.
PH = 7 + (1/2)(8.85+log0.01)= 10.4
6a. How many grams of NaH2PO4 (MW= 120) and NaHPO4 (MW= 142) would be required to prepare 1 liter of a buffer solution that has a target pH of 7.45 and an ionic strength of 0.100 M?
PH = PKa + log (base/acid) Ph= PKa + log (x/y) 7.45 = 7.21 + log (x/y) 0.24 = log(x/y) = 10^0.24 = 1.74 X= 1.74y [na+] = 2x + y [h2po4-] = x [hpo4-2] = y Ionic strength = (.5) (2x+y)(1^2)+ (x)(-2)^2 + (y)(-1)^2) = 3x+y = 0.1M 3(1.74y) +y = 0.1 Y= 0.016M X=.028M 120*0.028 = 3.36g 142*0.016 = 2.27g
5a. Calculate pKa for each base and which is weakest PKa = 4.6 PKa= 11.2
PKa = 4.6, Pkb = 2.8 stronger base PKa = 11.2 pkb = 9.4 weaker base
6b. Absorption of aspirin (MW= 180.3, pka= 3.4) into the blood stream occurs only when the molecule is in unionized form. If a patient has a stomach pH of 2.4 and takes two tablets of aspirin (325mg each) how many grams of aspirin are available for immediate absorption in the stomach? Would you expect more or less aspirin to be absorbed in the small intestines (ph 5.5-6.5)?
Part 1: how many grams of aspirin are available for immediate absorption in the stomach. Two tablets of 325mg = 650mg = 0.65grams Log (a/ha) = 2.4-3.4=-1 A/ha= .1 so HA/a- = 10 Ha = x a=y X=10y (X*180.2) + (y*180.2) =0.65grams (10y* 180.2) + (y*180.2) =0.65grams Y=3.28x10^-4moles X= 10y= 3.28x10^-3moles Weight for immediate absorption = HA = 3.28x10^-3moles * 180.2g/mole = 0.592 grams Part 2: The ph in the small intestines is higher than in the stomach therefore more aspirin is in the ionized form and less in the unionized form and there will be less absorption. =we know most of drug (91%) is in unionized form in the stomach
6a. What is the buffer pH when you dissolve 12.0g of NaH2PO4 (MW= 120) and 14.2 g of Na2HPO4 (MW= 142) in 2L of distilled water? What is the ionic strength of the buffer?
Part 1= find ph (12/120)/ 2 = 0.05 M (14.2/142.2)/2 = 0.05M H3P04 = H+ H2PO4- PKa1 = 2.12 H2PO4- = H+ HPO4-2. PKa2 = 7.21 PH = 7.21 + log (0.05/0.05) = 7.21 Part 2 = find ionic strength of buffer U = 1/2Zcizi^2 [NA+]= 0.05 + (2x0.05) = 0.15M [H2PO4-] = 0.05 [HPO4-2]= 0.05 U= (1/2) [(0.15)(1)^2 + (0.05)(-1)^2 + (0.05)(-2)^2)] = 0.2
5b. What is the pH of 0.1M KH2PO4 solution What is the ph of a 0.1 M K2HPO4 solution
Ph = (1/2)(2.1+7.1)= 4.6 Ph = (1/2)(7.1+12.3) = 9.7
5b. What is the ph of a 50mM sodium bicarbonate solution ka1= 4.3x10^-7 pKa2= 4.7x 10^-11
Ph = (1/2)(6.37+10.33)= 8.35 ampholyte solution [H]= square Ka1ka2 = 8.35
5a. What is the pH of 0.05 M HCl solution using hydronium ion concentration?
Ph = -log[0.05] = 1.3
5b. 0.2 M acetic acid solution (pka 4.76) find pH
Ph= 1.2 (pka - log c) = 1/2(4.76- log 0.2 ) = 2.73
6a. What is the pH of 500mL of solution that contains 0.05 mol of citric acid ANS 0.100 mol of monosodium citrate, if the pKa for the first ionization of citric acid is 3.13? Only first ionization is considered.
Ph= 3.13 + log (0.1/0.05) = 3.43
5b. What is the pH of 50mM KCl solution. Ignore effect of ionic strength
Ph= 7 due to strong acid and strong base
3. What is the strength of methadone in a solution containing 11mg methadone hydrochloride in each milliliter Methadone MW = 309. 4 HCl MW = 36.5
Salt factor = 309.4 + 36.5 / 309.4 = 1.1 Wt methadone = 11mg / 1.1 = 10mg
4b. If the freezing point of blood is -0.52*C, what is its osmotic pressure at 25*C?
Tf/Kf= Osmoles = 0.52/1.82 = 0.28 24.4 x .28= 6.63
2. Explain why 3,5 dihydroxybenzoic acid has the highest MP and 2,6 dihydoxybenzoic acid has the lowest MP
The hydroxyl groups at 2- and 6- positions in 2,6 dihydroxy benzoic acid can form two intra molecular hydrogen bonds with the carobxylic group. This will reduce the intermolecular interactions, resulting in lower melting point The hydroxyl groups at 3-5- positions in 3,5 dihydroxybenzoic acid cannot form intra molecular hydrogen bonds but can form intermolecular hydrogen bonds. This will increase the intermolecular interactions resulting in higher melting points
7. Which of the following statements below is true The thermodynamic solubility of a Drug needs to be determined using the amorphous form of the drug. The drug with high solubility in water must dissolve very fast. The kinetic solubility tends to decrease over time. No more drug can be dissolved in water than its thermodynamic solubility
The kinetic solubility tends to decrease over time
6b. Explain why aspirin pka=3.4 can be absorbed in the stomach (ph 1.9) but codeine pka7.9 cannot be absorbed. Note only nonionized form can be absorbed.
The percent of unionized form of aspirin in the stomach is : Log (A/HA) = 1.9-3.4= -1.5 (A/HA) = 10^-1.5 = 0.032 HA% = 1/1.032 *100% = 97% Most of aspirin is in the nonionized form in stomach and can be absorbed The percent of codependent in nonionized form in the stomach: Log(B/HB+) = 1.9-7.9 = -6 (B/HB) = 10^-6 which is super low value, basically nothing in nonionized form, therefore codeine is almost 100% ionized in stomach and cannot be absorbed.
4b. If you place red blood cells in a buffer solution that has higher osmolality than the cells which of the following is correct There is a higher pressure inside the cells and the cells will expand There is a lower osmotic pressure inside the cells and cells will expand There is a higher osmotic pressure inside the cells and the cells will shrink There is a lower osmotic pressure inside the cell and the cells will shrink
There is a lower osmotic pressure inside the cell and the cell will shrink
2. Oxygen and CO2 are exchanged between blood and air in alveoli, it is found that the partial pressure of oxygen in alveoli is only 100mmHg. Why is the partial pressure of oxygen is lower than that in the atmosphere?
This has to do with the presence of water and CO2 in alveoli
7. Aspiring has the lowest solubility in which of the following solvents Water Toluene Ethanol DMSO = do you think aspirin is more soluble in water or ethanol
Toluene Ethanol = aspirin has some hydrophobic organic moieties so ethanol is better than water which is specifically only polar without organic moieties
4b. If you need to prepare 30mL of 1% procaine HCl (E=0.21) solution. What is the volume of 0.9% NaCl solution that is needed to make the solution isotonic?
V= .3*.21*111.1 = 6.3 30-6.3= 23.7mL
7. What is the highest pH allowed to prepare a 1% morphine solution? MW = 285.35 pka = 7.87 Intrinsic solubility So = 0.1712 mg/ml
You know its a base because asking for the "highest ph allowed" S = 1% 1g/100ml = 1000mg/100ml = 10mg/ml Ph= pka +log (so/s-so) = 7.87 + log (0.1712/10-0.1712) = 6.11
7. What is the ph below which sulfadiazine (pka = 6.48) will begin to precipitate in an infusion fluid, when the initial molar concentration of sulfadiazine sodium is 0.04 mol/L and the solubility of sulfadiazine is 3.07 x 10^-4 mol/L
You know its an acid because its asking for "the pH below which" S= o.04 So=0.000307 Ph = pka + log (s-so/so)= 6.48 + log (0.04 -0.000307 / 0.000307)= 8.59
