FunSci Exam 1
Evaporation rates of liquids are [BLANK] proportional to the degree of association between molecules.
inversely That is, the stronger the intermolecular forces between liquid molecules the harder it is for them to fly to the gas phase and less volatile the liquid is, and vice versa.
Salting out...
is the presence of electrolytes decreases the solubility of nonelectrolytes and causes them to precipitate. This is called salting out. Salting out of nonelectrolytes occurs because electrolytes are charged molecules with a lot higher affinity for water molecules than nonelectrolytes. As a result, electrolytes decrease the number of water molecules available to solubilize the nonelectrolytes causing it to precipitate.
The most important thing to know about amphoteric compounds is that they precipitate at their...
isoelectric point.
If we see a basic tertiary nitrogen atom with its lone pair of electrons, then it tells us...
it has a basic center.
The dielectric constant (symbolized as ε):
it is an index of the molecule's polarity and it can be used to rank molecules according to their polarity.
Arrhenius Equation:
k = A e^(-Ea/RT)
The higher the BP the [BLANK] the VP at room temp.
lower
The longer the conjugated system, the [BLANK] the excitation energy.
lower
The stronger the interactions between the liquid molecules, the [BLANK] the vapor pressure of the liquid.
lower
High energy radiation is [BLANK] powerful than low energy radiation
more
For weakly basic drugs, their name usually ends with...
"-ine."
The osmolarity of biological fluids is 300±10 mOsm/L. Using the information on the difference between isosmotic and isotonic solutions, decide which of the following solutions is the safest for intravenous injection? Note: "FC" after a compound's name indicates that the compound can Freely Cross red blood cell membranes.
0.099M CaCl2 ( mol weight 110.98 g/mol) For a solution to be considered safe for intravenous injection, it has to be isotonic to red blood cells (i.e. it should not cause the cell to swell or shrink). For a solution to be isotonic, it has to have the same osmolarity (300±10 mOsm/L) as blood AND all solutes it contains should not be able to cross red blood cells membranes. In order to know the osmolarity of a solution we need to convert the concentration expression given to osmolarity using either of the following two equations: for electrolytes; Osmolarity in mOsm/L = #ions × ((g / L) / mol. wt.) × 1000, OR for non-electrolytes; Osmolarity in mOsm/L = ((g / L) / mol. wt.) × 1000
Using the freezing point depression method, how much sodium chloride is needed to make the following solution isotonic to blood and biological fluids knowing that the ΔTf1% for Procaine HCl is 0.122? Procaine HCl.........................2% Purified water ad......................30mL
0.143 g Use the ΔTf1 equation above, but you need to correct for the percentage concentration and final volume. When calculating the amount of NaCl to make a solution isotonic to biological fluids using the cryoscopic method we pay attention to two things; 1) the final concentration of the solution, and 2) the final volume of the solution as described in the prescription. For the final concentration of the solution: ∆Tf1 values you get from literature is the drop in the freezing point of water caused by 1% w/v solution of the drug. Therefore, when using the cryoscopic equation the first thing to check for is the concentration of your ingredient in the prescription. If the PERCENTAGE concentration of the drug is not 1%, we will have to adjust the ∆Tf1 value given as will be explained below. Notice the concentration has to be in percentage w/v. If given in any other expression, convert it to % w/v. For solution volume: the equation allows you to calculate the amount of NaCl in grams needed for each 100mL final solution volume. So, the second thing I look at is solution volume in the prescription. If the prescription calls for more or less than 100mL solution volume, we need to adjust the grams of NaCl needed accordingly as will be shown below. Step 1, check the concentration of your active ingredient to see if it is 1% or more or less. The concentration of procaine HCl here is 2%w/v. Since the concentration of procaine HCl in this solution is 2%, we can not use the ∆Tf1% value as provided because it assumes a 1% solution only. Therefore, we have to calculate the depression in the freezing point of water caused by the 2% solution first: 1% solution of sod salicylate has a ∆Tf1% = 0.122, therefore 2% solution will have .............∆Tf2% = X X = 2 * 0.122 = 0.244 We then can use the calculated ∆Tf2 value in the equation to get the amount of NaCl in grams. Step 2, check solution volume in the prescription, if the prescription calls for 100mL no adjustments will be necessary. If more or less we will need to correct for the volume difference. Here, the prescription calls for a final volume of 10mL. So, whatever grams NaCl you get, you have to divide by 10. We use the value calculated above (0.244) as our ∆Tf in the equation above to calculate the grams of NaCl needed per 100 mL solution as follows Grams of NaCl needed in 100mL soln. = [0.9 × (0.52 - 0.244)] / 0.52 = 0.4776923 g But be careful because the 0.4776923 g NaCl are needed for 100 mL and the prescription calls for 30 mL. So, for this prescription we will need 0.4776923*30 / 100 = 0.143 g NaCl.
If 0.3g sodium chloride was needed to make an ophthalmic solution isotonic but there was no sodium chloride available, using the "E value method," what is the amount of boric acid needed to make the solution isotonic knowing that the E value for boric acid is 0.5?
0.6g the E value for boric acid is 0.5. therefore, 0.5g NaCl is equivalent to 1g boric acid; and 0.3g NaCl is equivalent to ??? boric acid ??? = 0.3 / 0.5 = 0.6g boric acid
Fluorouracil (mol. wt. = 130.08g/mol) is an anticancer agent. The formulation below is intended to be applied on precancerous lesions of the skin. Knowing that the E value for fluorouracil is 0.13 and using the "E value method," what is the amount of sodium chloride needed to render the solution below isotonic? Fluorouracil ..................... 1g Sterile water q.s. ad. ............ 100mL M. Ft. topical solution
0.77g use the sodium chloride equivalent method as follows: X = E × weight in grams = 0.13 × 1 = 0.13 Y = (0.9 / 100) × volume of your solution = 0.9 / 100 × 100 = 0.9 Grams sod. chlor. = Y - X = 0.9 - 0.13 = 0.77g
What is the osmolarity of a solution that is 0.25M in NaBr and 0.15M in Na2SO4?
0.95 osmol/L The total osmolarity of a solution is the sum of the individual osmolarities for each solute in the solution. So, we need to convert the concentration of each solute in the solution to somoalrity and then add them up. For our solution, (0.25M*2) + (0.15M*3) = 0.95 osmol/L
The three different categories based on their dielectric constants are...
1) Polar solvents: these are solvents with dielectric constants of 50 or more. They are capable of dissolving ionic or polar solutes. 2) Nonpolar solvents: these are solvents with dielectric constants of 20 or less. They are incapable of dissolving ionic or polar solutes. 3) Semipolar solvents: these are solvents with dielectric constants between 20 and 50. Their ability to dissolve ionic or polar solutes is less than polar solvents. ▪ Semipolar solvents are mostly non-polar liquid molecules BUT they do have some polar groups that allow them to interact with ions or other polar molecules.
Factors that affect the solubility of a drug:
1) polarity of solute (and solvent) 2) pH 3) temperature
Disadvantages of solution dosage forms:
1) poor chemical stability of active ingredients, especially in aqueous media: drugs with ester or amide bonds, for example, hydrolyze easily in aqueous media and lose their effectiveness. 2) poor solubility of some active ingredients. 3) inconvenient to transport and carry around since containers are bulky and may break or leak.
What are the advantages of solution dosage forms?
1) rapid onset of actions, which leads to faster relief of symptoms as explained above. 2) accurate and consistent dosing due to the uniform and homogenous distribution of active ingredients in the vehicle (i.e. solvent). 3) aqueous solutions are the only dosage form that can be injected IV, which is extremely important in emergency situations where an immediate response is needed.
Standard buffer solutions should:
1. Be prepared with CO2-free water: this is because CO2 is an acidic gas; it is present in the atmosphere and it dissolves in water giving carbonic acid which lowers the pH. 2. Be stored in type I glass tight containers: this is because type I glass does not adsorb ions in solutions and it does not release ions into solutions. Containers should be tightly closed to minimize leakage of CO2 which may lower the pH.
If we know the pKa of our drug, then we can adjust the pH of the solution so that all the molecules are in the desired form. How?
1. For weakly acidic drug, if the pH of the solution is higher than the pKa of the acidic drug the drug will exist mostly in the ionized (charged) state. But if the pH is less than the pKa, the drug will mostly be neutral. 2. For weakly basic drugs, if the pH of the solution is higher than the pKb of the basic drug the drug will exist mostly in the neutral state. But if the pH was less than the pKb, the drug will mostly be ionized (charged). 3. For either type of drug, if the pH = pKa (or pKb for bases) the drug will be 50% ionized. (To raise the pH we add a base and to lower it we add an acid.)
How can we utilize the ionization and absorption rules we just discussed to enhance the effectiveness and the overall performance of pharmaceutical products containing aspirin?
1. Think of the route of administration (i.e. the way the patient is going to take this solution). Since this solution is intended for oral use, that means the way it enters the main circulation is through the GIT. So, the keyword here is "absorption." 2. To achieve faster and better pharmacological response, we need to maximize the absorption of our active ingredient. Remember the rule: "the neutral (or uncharged) form of drugs is the one that is maximally absorbed." So, for this oral solution of aspirin, we need to promote the neutral form to get better absorption. 3. We can make a generalization here and say that for all orally administered drugs we should promote the neutral form of the weak acid/basic drug to obtain better absorption. However, it is not that simple because often times the neutral form of the drug is the least soluble in water and we do need to maximize solubility to enhance absorption. So, it is a delicate balance between charged and neutral forms we need to achieve to enhance solubility and maximize absorption. 4. Figure out how to prevent the ionization of aspirin molecules in the solution.
A pharmaceutical solution containing active ingredient A showed an absorbance value of 1.1. If the molar absorptivity of ingredient A is 10677 mol-1 cm-1, approximately, what is the molar concentration of ingredient A in this solution?
1.03×10-4 M From Beer's law, C = A / (epsilon X1) = 1.1 / 10677 = 1.03×10-4M From Beer's law, A (which is the absorbance) = epsilon × b × C. By rearrangement, C = A / (epsilon × b). "A" is provided in the question, it is 1.1. As we all know, "b" is always 1 unless otherwise stated.
Methicillin is a weakly acidic drug with a Ka of 9.77×10 - 4. What is the pH of a methicillin solution that has a concentration of 125 g/L knowing that the molecular weight of methicillin is 380.4 g/mol?
1.7 First thing, we need to convert concentration to molarity: 125 g/L = 125/380.4 = 0.328601472 M Then, we use the equation for weak acids to calculate the [H+] [H+] = √0.3286 × 9.77×10 - 4 = √0.0003210436382755 = 0.017917691 Then we calculate the pH as follows: pH = -log 0.017917651 = 1.7
A cold cream is an emulsion for softening and cleansing the skin. A cold cream is to be prepared using mineral oil and water in the ratio of 1 to 1. Calculate the amount of benzoic acid to be incorporated into the emulsion in order that a concentration of 0.25 mg/mL of the bacteriostatic form of benzoic acid remains in the aqueous phase which is buffered at pH 4.0. Ka for benzoic acid is 6.4 × 10-5 and its oil/water partition coefficient is 5.33.
1.7mg per mL emulsion We use the equation [HA]w = C / [(Po/w q + 1 + Ka / [H3O+])] The bacteriostatic form is the unionized form of the acid which is [HA]w which, as stated in the question, is 0.25mg/mL. Therefore, here we are solving for C which is the concentration of the preservative we need to have in the aqueous phase before adding the oil phase (because after adding the oil, some of the preservative will escape to the oil phase and the concentration of the preservative in the aqueous phase will drop). After rearranging the equation above to calculate for "C", we get the following: So, rearrange the equation to C = (Po/w q + 1 + Ka / [H3O+]) [HA]w = [(5.33 × 1/1) +1+(6.4 × 10-5/10-4)] 0.25 = [6.33 + 0.64] × 0.25 = 6.97 × 0.25 = 1.7mg/mL IMPORTANT NOTE: in using this equation, note that we have two concentration terms; the bacteriostatic concentration which is [HA]w and the total concentration of the preservative in both the oil and water phases which is C. So, if we use [HA]w in mg/mL, we will get the C in mg/mL. If we convert [HA]w to molar units, we will get C in molar units as well. In this problem we kept [HA]w in mg/mL units because all the answer choices are units of mg/mL.
Good absorption a drug should be...
10-1000 more lipophilic.
Using the White-Vincent method, how much water you need to prepare the initial concentrated solution and how many mLs of the isotonic solution you need to use to make the following solution isotonic with respect to blood and biological fluids? The E value for homatropine hydrobromide is 0.17 and the E value for chlorobutanol is 0.24. Homatropine hydrobromide......................1% Chlorobutanol......................................0.2% Purified water ad............................50mL
12.11 mL of water are needed for the initial concentrated solution and the volume of isotonic solution to be added is 37.89 mL You will need to apply the White-Vincent equation shown above to get the volume of the initial concentrated solution and then subtract that from 50 mL to get the volume of the isotonic solution you need to add. You have to be careful with one thing. The concentrations in the prescription are give in % which means g per 100 mL solution. The prescription calls for a final volume of only 50 mL which is half of the 100 mL. So, we need to half the mounts given in % concentration. For the homatropine the weight to use in the equation, therefore will be 0.5 g and for the chlorbutanol the weight should be 0.1 g.
UV light with wavelengths from [BLANK] to [BLANK].
290 to 400nm
Pilopine HS® is an ophthalmic aqueous gel that is used to control the intraocular pressure. It contains the active ingredient pilocarpine hydrochloride at the concentration of 4% w/v. Use the appropriate equation to calculate what is the pH of this gel if the molecular weight of pilocarpine chloride is 244.72 g/mol and the pKb of pilocarpine = 7.2?
3.8 Three things we need to do to answer this question correctly: First determine what type of salt this is to decide what equation to use Pilocarpine HCl is a salt of weak base and strong acid Therefore, use equation pH = ½ pKa - ½ log [salt] We also need to convert the concentration to molarity 4% = 4g/100mL = 40g/1000mL = 40 g/L = 40/244.72 = 0.16345211 M Lastly, we need to realize that we are provided with the pKb of our base but we need the the pKa to use in the equation pKa = 14 - 7.2 = 6.8 Now, since we have all the numbers we need, we can solve our equation to calculate the pH of this gel. pH = 6.8 / 2 - ½ (log 0.16345211) = 3.4 - ½ (-0.78661)= 3.4 - (-0.393305) = 3.79 = 3.8
You have a 1Eq/L potassium acetate (CH3COOK) stock solution. You work in a hospital and you were requested to add 40 mEq of potassium acetate to an IV bag. How many milliliters of the stock solution will you add to the bag?
40mL First of all, we need to make all units the same. We can not do the calculations when some units are in Eq while others are in mEq. Remember, 1 Eq = 1000 mEq and 1 L = 1000 mL. The stock solution is 1Eq/L which means it contains 1000 mEq in each 1000 mL To answer this question then, we set up a proportion and solve for the unknown: X mL/40 mEq = 1000 mL/1000 mEq X mL = 40 mEq (1000 mL/1000 mEq) = 40 mL
Solutions of SA-SB salts in water will have a pH of [BLANK] unless some other pH altering substances are present.
7
What is the equivalent weight of sodium sulfate (Na2SO4, Mol. Wt. = 142.04 g/mol) if used for its sulfate content?
71.02 g/Eq Sodium sulfate has two sodiums and one sulfate SO4--. Each sodium loses one electron (for a total of 2 electrons lost) to become Na+ whereas the sulfate gain those electrons. This make the # of electrons exchanged = 2. We then use the equation Eq. Wt = Mol. Wt./# electrons exchanged
Which of the following is the pH below which the neutral form of ketoprofen precipitates from a 0.037 M solution of ketoprofen sodium (276.26 g/mol). The aqueous solubility of ketoprofen is 5.6×10- 4 mole/L and it has a pKa of 4.6. Select one: a. 6.4 b. 1.5 c. 3.0 d. 5.9 e. 7.0
A 0.037 M is our S and 5.6×10- 4 M is our So Use the equation for weakly acidic drugs: pHp = pKa + log [ ( S - So ) / So ] pHp = 4.6 + log [(0.037 - 5.6×10-4) / 5.6×10-4] = 4.6+log[0.03644/5.6×10-4]=4.6+log 65.07=4.6+1.8=6.4 Therefore, below pH 6.4, the free (i.e. the neutral) form of ketoprofen will precipitate from the 0.037 M solution of ketoprofen sodium.
What is the pH of a 3% solution of atropine sulfate knowing that the molecular weight of atropine sulfate is 676.8 g/mol and the pKb of atropine base is 4.35? Select one: a. 5.5 b. 4.6 c. 11.1 d. 1.9 e. 2.9
A 1) For all pH calculations, the concentration has to be in Molarity, if not, convert it. the concentration here is 3%. We need to convert that as follows: 3% = 3g/100mL = 30g/1000mL = 30 g/L = 30/676.8 = 0.04433 M 2) Next, determine what type of salt this is to decide what equation to use. The strong acids we know are only 3; sulfuric, hydrochloric, and nitric. The strong bases we know are the metal hydroxides (e.g. sodium hydroxide, potassium hydroxide, calcium hydroxide, ...). Any other acid or base are weak ones. Atropine sulfate, therefore, is a salt of weak base (atropine) and strong acid (sulfuric acid) Therefore, we use equation pH = ½ pKa - ½ log [salt] I highlighted the pKa because in the question, we are provided the pKb. So, we need to convert the pKb provided to pKa. Only in calculating the pH of this type of salt we do this conversion but this is an easy fix. 3) Lastly, we need to realize that we are provided with the pKb of our base but we need the the pKa to use in the equation pKa = 14 - 4.35 = 9.65 Now, since we have all the numbers we need, we can solve our equation to calculate the pH of this solution. pH = 9.65 / 2 - ½ (log 0.04433) = 4.825 - ½ (-1.3533)= 4.825 - (-0.67665) = 5.50
A mixture of phenol and water containing 7% phenol by weight was prepared at room temperature such that the two liquid existed as a clear solution with only one liquid phase. Which of the following is the most likely outcome If 5g of potassium sulfate was added to this solution? Select one: a. the solution will break into two liquid phases b. the potassium sulfate will precipitate c. the solution will remain as a single homogenous phase
A Potassium sulfate is more soluble in water than it is in phenol which will cause the system to break into two separate liquid phases. When a third substance is added to a solution of two partially miscible liquids it can either further stabilize the solution or cause it break into two phases depending on how soluble this third substance is in each of the two liquids. If that third substance is equally soluble in the two liquids, it will further stabilize the solution. If it is preferentially soluble in one of the two liquids, it will cause the system to break into two liquid phases.
Dimethyl sulfoxide is a liquid with a dielectric constant of 46.7. Which of the following statements is true about dimethyl sulfoxide? Select one: a. Dimethyl sulfoxide is a semi-polar liquid. b. Dimethyl sulfoxide is a polar liquid. c. Dimethyl sulfoxide is a nonpolar liquid.
A Since dimethyl sulfoxide has a dielectric constant that is less than 50 and more than 20 it is consderdd a semi-polar solvent. The dielectric constant of a substance is a measure of its polarity. Solvents with dielectric constant of more than 50 are considered polar solvents, solvents with dielectric constants of 20 or less are considered as non-polar solvents, and solvents with dielectric constants of between 20 and 50 are described as semi-polar solvents.
Decide which of the following will decrease urine pH? Select one: a. potassium dihydrogen phsophate b. calcium chloride c. dextrose d. sodium bicarbonate
A Urine acidifiers decrease urine pH to below 7. An example is potassium dihydrogen phsophate.
What are the strong acids we know?
sulfuric, hydrochloric, and nitric acids. All other acids are weak.
An antibacterial drug has a pKb of 7 and the dielectric constant of 30 for its neutral form. Which of the following is the best vehicle choice if we are to prepare for oral administration a solution of this drug containing the neutral form to treat systemic infections? Select one: a. a solvent mixture composed of 20% water, 20% ethanol, and 60% carbon tetrachloride b. a solvent mixture composed of 5% water, 80% ethanol, and 15% glycerol c. borate buffered saline that has a pH of 8.0 and a buffering capacity within the recommended range d. phosphate buffered saline that has pH of 6.4 and a buffering capacity within the recommended range
B Both ethanol and glycerol are safe if taken internally and this solution will contain the neutral form of the drug which is easily absorbed from the GIT into the blood stream and, hence, more effective in treating systemic bacterial infections. For oral solution, they need to contain the neutral form of a weak electrolyte drug for maximum absorption from the GIT. Since this drug is a basic one (we were given a pKb) whose pKb is 7, we need the solution pH to be 7 or above. Also, since water (the solvent in this oral solution) has a dielectric constant of 80 and the drug has a dielectric constant of 30, we need to add some safe organic solvents to the solution to bring the overall dielectric constant down and close to 30. Because we need to use a buffer, it has to be safe for internal use in humans. Cell membranes in the different tissues in the body (especially the red blood cells membranes) are permeable to boric acid.which means if a solution of boric acid was given internally (i.e. by mouth or IV injection) it will cause cells in these tissues to swell and increase in size and may burst (even if it has the same osmolarity as blood) which is harmful. The exception to this is cells in the eyes. Membranes of cells in the eyes are impermeable to boric acid which means solutions of boric acid that have the same osmolarity as blood and biological fluids are isotonic to cells in the eyes (i.e. will not cause those cells to swell or change in size. This is why boric acid solutions are toxic if given internally but are safe to use in the eyes.
Which of the following is the best example of a chromophore? Select one: a. A chemical group that emits UV or visible light b. A chemical group that absorbs UV or visible radiation c. A chemical group that absorbs radio waves or microwaves d. A chemical group that absorbs IR or microwave radiation
B Chromophores are the chemical groups that allow a molecules to absorb light in the UV-Visible region and not other types of radiation. Chromophores absorb UV or Visible light.
Choose from the answer choices below the group of words that best completes the following sentence: Fluorophores, such as ____________, are chemical groups that allow molecules to ____________ electromagnetic radiation. Select one: a. acetone, emit b. coumarins, emit c. carbonyl groups, emit d. acetone, absorb e. coumarins, absorb
B Fluorophores are chemical functional groups that, when get excited, emit electromagnetic radiation to go back to the ground state causing the molecule to glow. Usually, these groups are flat and planar aromatic structures. Coumarins are flat, planar aromatic groups that upon excitation, they lose the acquired excitation energy by emitting electromagnetic radiation allowing molecules containing them to glow.
Decide which of the following spectroscopic techniques is most effective in detecting and quantitating heavy metals such as arsenic in pharmaceutical preparations? Select one: a. Fluorescence spectrophotometry b. Atomic absorption spectrometry c. NMR d. Polarimetry
B In order to detect and quantitate heavy metals in a pharmaceutical sample, you need a technique that is so specific that it can tell you exactly what heavy metal is present and how much of it is there. Of all the techniques we studied, only atomic absorption spectrometry determines the absorption of individual atoms which means there will be no interference by chromophores in other molecules. This makes atomic absorption the only technique we learned about that is specific enough to identify what heavy metal is present. At the same time, because absorption is proportional to concentration, the height of the peak can be used to determine how much of the metal is present. UV absorption techniques that measure absorption of molecules may tell you if a particular heavy metal is present but they are not specific because so many different chromophores in molecules absorb in the UV region which will mask the heavy metal peak. Because in atomic absorption spectrometry you measure the absorption of individual atoms, there will be no interference by chromophores from other molecules and the peaks you see on the spectrum are specific to elements in the periodic table. This allows for identification of metals present.
Decide which of the following electromagnetic radiation you expect to do the most harm to tissues and most likely to cause cancer in humans? Select one: a. A radiation with a frequency between 1013 Hz and 1016 Hz b. A radiation with a frequency of 1017 Hz or higher. c. A radiation with a wavelength of 100 μm or longer d. A radiation with an energy value between 1 kcal/mol and 30 kcal/mol
B The higher the energy of a radiation, the more damage it causes to atoms in tissues which leads to cancer. The energy of a radiation is directly proportional to its frequency but inversely proportional to its wavelength.
The vapor pressure of a liquid pharmaceutical is __________ __________ to ___________ _________ between its molecules. Select one: a. Inversely proportional, the kinetic energy b. inversely proportional, the attractive forces c. directly proportional, the degree of polarity d. directly proportional, the degree of association e. inversely proportional, the degree of branching
B The stronger the bonds between the molecules of a liquid pharmaceutical the harder it is for the individual molecules to break apart and fly to the gas phase. In addition, the lower the number of molecules in the gas phase the less pressure they generate.Therefore, the stronger the bonds between the molecules of a liquid pharmaceutical the lower its vapor pressure. In other words, the vapor pressure of a liquid pharmaceutical is inversely proportional to the attractive forces between its molecules. The vapor pressure of a liquid is inversly proportional to the degree of associations (attractive forces) between molecules. High degree of associations between liquid molecules prevent them from escaping the liquid phase which leads to less vapor pressure.
Decide which of the following will increase urine pH? Select one: a. potassium chloride b. sodium bicarbonate c. sucrose d. sodium dihydrogen phosphate
B Urine alkalinizers increase urine pH to above 7. An example is sodium bicarbonate.
A polar non-electrolyte antiseptic drug is to be prepared in aerosol form to be sprayed on the skin at room temperature. For best functioning of the valve system, the pressure inside the can should be at least 1 pound per square inch (psi). You have a choice of two propellant mixtures, I and II as shown below: Propellant mixture I contains: 60 g of prop1 + 40 g of prop2 Propellant mixture II contains: 60 g of prop1 + 40 g of prop3 Decide which of these propellant mixtures (I, or II) you would use to prepare this antiseptic aerosol? Additional information you may need: Prop1 has a molecular weight of 18.0 g/mol and a vapor pressure of 0.35 psi at room temperature. Prop2 has a molecular weight of 46.1 g/mol and a vapor pressure of 1.8 psi at room temperature. Prop3 has a molecular weight of 58.1 g/mol and a vapor pressure of 4.35 psi at room temperature. Select one: a. propellant mixture I b. either I or II will work c. propellant mixture II d. neither I nor II will work
C For mixture I: moles of prop1 = 60/18 = 3.3 moles moles of prop2 = 40/46.1 = 0.87 moles total moles = 3.3+0.87=4.17 Xprop1 = 3.3/4.17= 0.79 Xprop2 = 0.87/4.17=0.21 Pprop1= 0.35*0.79= 0.2765 psi Pprop2= 1.8*0.21= 0.378 psi Ptotal=0.2765+0.378= 0.6545 psi For mixture II: moles of prop1 = 60/18 = 3.3 moles moles of prop3 = 40/58.1 = 0.69 moles total moles = 3.3+0.69=3.99 Xprop1 = 3.3/3.99= 0.83 Xprop3 = 0.69/3.99=0.17 Pprop1= 0.35*0.83= 0.2905 psi Pprop3= 4.35*0.17 = 0.7395 psi Ptotal=0.2905+0.7395= 1.03 psi Therefore, we choose mixture II
Didanosine is a purine nucleoside analogue approved for the treatment of HIV infections. It is extremely unstable at pH values less than 3 and requires protection against gastric acid induced inactivation by hydrolysis. Which of the following is the best approach to maximize the stability and the effectiveness of didanosine if it is to be administered orally in tablet or capsule forms? Select one: a. coating didanosine tablets/capsules with a layer of lipid such as parafin wax b. advice patients to take an antacid tablet before taking didanosine tablets/capsules c. coating didanosine tablets/capsules with a layer of an acidic polymer that has a pKa of 5.5 d. prepare didanosine in solution form buffered at pH 7 for oral administration e. coating didanosine tablets/capsules with a layer of an acidic polymer that has a pKa of 9.5
C This is the best approach. Coating the tablet with an acidic polymer with a pKa of 5.5 will guarantee the tablet will not dissolve in the stomach (see pH rules above) which will offer maximum protection of the active ingredient. At the same time, a polymer with this pKa means it will dissolve in the intestine which is what we need to release the active ingredient for absorption. The general rules are: 1- For acidic substances, if the pH of the solution is higher than the pKa of the acid, the acid will exist mainly in the ionized form (which is the soluble form). 2-For basic substance, if the pH of the solution is less than the pKb of the base, the base will exist mainly in the ionized form (which is the soluble form).
The chemical functional groups that cause molecules to absorb UV or visible light are called [BLANK].
Chromophores
Which of the following is caused by uncontrolled exposure to IR radiations? Select one: a. Cancer b. No effect, IR radiations are harmless to humans c. Photoaging d. Burns
D IR radiatins are of relatively low energy. They can only induce vibrational motion in molecules (due to bond stretching and angle bending) which generates heat that causes burns. Because IR radiations cause bond stretching and angle bending in molecules, they induce motion in molecules which generates heat due to friction, thus, causing burns
Which of the following is the best example of "salting-in"? Select one: a. we can dissolve more atropine in buffers with pH values of less than 7 than we can in buffers with pH values of more than 7 b. we can dissolve more of the amorphous form of a solid drug in water than we can of its crystalline form c. we can dissolve more sucrose in hot water than we can in cold water d. we can dissolve more nucleic acids (DNA and RNA) in dilute MgCl2 solutions than we can in plain water
D Salting-in refers to the effect of increasing the solubility of non-electrolytes (e.g. proteins) by adding electrolytes (i.e. ions) to the solution. The non-electrolyte here are the nucleic acids and the elcetrolyte is MgCl2. Salting-in refers to the effect of increasing the solubility of non-electrolytes (e.g. proteins) by adding electrolytes (i.e. ions) to the solution. As explained in the notes, a good example is the increase in the solubility of proteins like immunoglobulins (the non-electrolyte) in solutions containing ions like sodium chloride (the electrolyte).
Sunscreens can block the harmful effects of sunlight by which of the following mechanisms? Select one: a. Emit electromagnetic radiation with wavelengths between 0.2-0.4 μm b. Emit electromagnetic radiation with wavelengths between 0.4-0.8 μm c. Absorb all electromagnetic radiation emitted by the sun d. Absorb electromagnetic radiation with wavelengths between 0.2-0.4 μm e. Absorb electromagnetic radiation with wavelengths between 0.4-0.8 μm f. Emit electromagnetic radiation with wavelengths between 0.8-100 μm
D Sunscreens are molecules that have pi electrons that are part of a conjugated system that is 7-8 bonds in length. In addition, they have atoms with lone pairs of electrons (non-bonded). These functional groups mostly absorb radiation with wavelengths between 290nm and 400nm which are UV wavelength that are the most harmful wavelengths that reach us here on earth. The wavelengths stated in this answer choice overlap the absorption range of sunscreens.
From the group of words below, select the ones that best complete the following sentence: A __________ is the instrument used to measure the angle of rotation. Select one: a. fluoremeter b. spectrophotometer c. refractometer d. polarimeter
D The degree of rotation of plane polarized light is measured by an instrument called the polarimeter.
The amorphous form of a drug: Select one: a. is usually less soluble than the crystalline form b. is usually more ordered than the crystalline form c. usually has a sharp and well defined melting point d. is usually more biologically active than the crystalline form
D The molecules of solid active ingredients in the amorphous form do NOT arrange in any specific order and, hence, the polar groups are fully exposed and accessible to water. This usually makes the amorphous form of the drug more soluble and, hence, more biologically active than the crystalline form. Also, since the molecules are not arranged in any particular order with varied degree of association between them, they do not necessarily melt. They soften. The amorphous form is more soluble. Because it dissolves fast, it shows faster and more complete absorption which leads to better biological activity than the crystalline form.
One of the sterilization methods used to sterilize surgical tools or medical equipments in medical centers is by boiling in water containing a bactericidal agent for 20-30 mins at 100 ⁰C. If you work in a medical center and in charge of sterilizing surgical tools and utilizing what you know about the relationship between intermolecular forces and boiling points and vapor pressures, which of the following bactericidal agents you can add to water to effectively sterilize surgical tools? Select one: a. Ethyl alcohol (B.P. 78.4 ⁰C) b. Phenol (B. P. 181.7 ⁰C) c. Cetylpyridinium chloride (melting point 83 ⁰C) d. b) or c) e. a) or c)
D The weaker the intermolecular forces, the easier for molecules to move around and to fly to the gas phase. Flying to the gas phase increases the vapor pressure on top of the liquid and lowers the boiling point of the liquid. If a compound boils at low temperature, it will not stay in solution for long enough time to produce biological activity. The correct answer is: b) or c)
An antibacterial drug has a pKb of 7 and the dielectric constant for its neutral form is 30. Which of the following is the best vehicle choice if we are to prepare an ophthalmic solution containing the neutral form of this drug to treat eye infections? Select one: a. phosphate buffered saline that has pH of 6.4 and a buffering capacity within the recommended range b. a solvent mixture composed of 5% water, 80% ethanol, and 15% glycerol c. a solvent mixture composed of 20% water, 20% ethanol, and 60% carbon tetrachloride d. borate buffered saline that has a pH of 8.0 and a buffering capacity within the recommended range
D This is because of 2 reasons: 1) Boric acid solutions (the isotonic ones) are safe to use in the eyes. 2) the pH of this buffer is higher than the pKb of this basic drug which means the drug will be mostly in the neutral state. The neutral state is needed here because, since this is an antibacterial drug, it can penetrate bacterial cell membranes easier and, hence, will be more effective in treating the infection. For ophthalmic bacterial infections, this solution should contain the neutral form of a weak electrolyte drug for maximum diffusion into bacterial cells (otherwise, it won't be able to inhibit bacterial growth). Since this drug is a basic one (we were given a pKb) whose pKb is 7, we need the solution pH to be 7 or above. Also, since water (the solvent in this oral solution) has a dielectric constant of 80 and the drug has a dielectric constant of 30, we need to add some safe organic solvents to the solution to bring the overall dielectric constant down and close to 30. Cell membranes in the different tissues in the body (especially the red blood cells membranes) are permeable to boric acid.which means if a solution of boric acid was given internally (i.e. by mouth or IV injection) it will cause cells in these tissues to swell and increase in size and may burst (even if it has the same osmolarity as blood) which is harmful. The exception to this is cells in the eyes. Membranes of cells in the eyes are impermeable to boric acid which means solutions of boric acid that have the same osmolarity as blood and biological fluids are isotonic to cells in the eyes (i.e. will not cause those cells to swell or change in size. This is why boric acid solutions are toxic if given internally but are safe to use in the eyes.
A 1M solution of glucose has an osmotic pressure of 1atm. If a 1M solution of an unknown drug has an osmotic pressure of 4atm, the unknown drug is most likely which of the following? Select one: a. CaCl2 b. Sucrose c. Ca3(PO4)2 d. NaCl e. K3PO4
E In dealing with colligative properties, we need to keep in mind that the value of a colligative property is proportional to the number of particles in a solution. This means that, if a solution containing a non-electrolyte substance like glucose (only one particle present) had an osmotic pressure 1 atm, a solution with an osmotic pressure of 4 atm would contain four times as many particles (i.e. an electrolyte that ionizes to four ions).
Based on the difference between isosmotic and isotonic solutions, choose from the choices below the answer that best completes this sentence: A 300 mOsm urea solution is __________ Select one: a. isosmotic to a 600 mM solution of NaCl b. isosmotic to a 200 mM solution of NaCl c. hyperosmotic to a 200 mM solution of NaCl d. isosmotic to a 0.18 % solution of NaCl e. hyposmotic to a 200 mM solution of NaCl
E Urea is a non-electrolyte which means the number of ions is 1. On the other hand NaCl is an electrolyte that dissociates into two particles; Na+ and Cl-. To convert the molarity of NaCl solutions to osmolarity, therefore, we have to multiply its molarity by 2. If the concentration of one of the solutions was given in any other expression than osmolarity, we need to convert it to osmolarity using either of the equations given above so that we can compare the osmolarities of the solutions involved. If two solutions have the same osmolarity, they are described as isosmotic. If one of them has higher osmolarity than the other, the one with higher osmolarity is described as hyperosmotic to the one with the lower osmolarity which, in this case, will be described as hyposmotic to the one with the higher osmolarity.
Ascorbic acid (vitamin C) is a weakly acidic vitamin that is freely soluble in water. Its aqueous solutions, however, are too acidic to administer by the parentral route. Because it is administered in relatively high doses, it can be used to buffer its own solution at the physiological pH. The acidity of ascorbic acid is partially neutralized by adding sodium carbonate according to the reaction: Ascorbic acid + Na2CO3 ---------> Na ascorbate + CO2 + H2O Thus, the injectable product contains sodium ascorbate, and ascorbic acid. If the Ka of ascorbic acid is 5×10-5, what is the molar ratio of sodium ascorbate to ascorbic acid required to prepare an injectable solution with a pH of 7.4? Select one: a. 502377286302 : 1 b. 2000 : 1 c. 25115973 : 1 d. 500 : 1 e. 1259 : 1
E Using the Henderson-Haselbalch equation for a weak acid and its salt 7.4 = -log Ka + log ([salt] / [acid]) = 4.3 + log ([salt] / [acid]) so, little rearrangement and simple math will give us3.1 = log ([salt] / [acid]) from which and by taking the antilog on both sides, 1259 = [salt] / [acid] so the molar ratio is 1259 moles of Na ascorbate for each 1 mole of ascorbic acid. Here, the solution contains a mixture of ascorbic acid (a weak acid) and sodium ascorbate (the sodium salt of ascorbic acid) which constitutes a buffer. Therefore, we use the equation for acidic buffers to calculate the pH. But we are not interested in the pH, in fact we have a target pH we want to achieve which is the physiologic pH of 7.4. We are also provided with the pKa of ascorbic acid. So, what we need to figure out is the ratio of [salt] / [acid] that allows us to obtain a pH of 7.4.
Rate (dc/dt):
Expression of the velocity or speed of a reaction, where dc is the change in conc. over an infinitesimal time interval dt. A + B + ... Products Rate = - d[A]/dt = - d[B]/dt = k [A] [B] Example: CH3COOC2H5 + NaOH CH3COONa + C2H5OH 5 Rate = - d[CH3COOC2H5]/dt = - d[NaOH]/dt = k [CH3COOC2H5]1 [NaOH]1 The reaction is First order with respect to CH3COOC2H5, First order with respect to NaOH, Second order overall. If NaOH kept in great excess; [NaOH] ~ constant Rate = k' [CH3COOC2H5], where k' = k [NaOH] Reaction: pseudo-first order
TRUE or FALSE: Aqueous solutions of aspirin are more stable than the tablet form.
False In general, active ingredients are less stable in aqueous media than they are in the dry form. Not true. In general, active ingredients are less stable in aqueous media than they are in the dry form.
TRUE or FALSE: polymorphic drugs can exist in the crystalline or amorphous states.
False Not correct because polymorphic drugs exist in multiple crystal forms.
What is the isoelectric point?
For an amphoteric molecule, the isoelectric point is the pH at which the amphoteric molecule has a net charge of zero and it would precipitate.
To calculate the pH of a solution containing a weak acid and a stronger acid, we use the [BLANK] for the stronger acid to calculate the pH and ignore all weaker acids.
Ka
Zero-Order Reactions:
Rate expression: - dc/dt = ko Integrated Equation: C = Co - kot C : Conc. at time t Co: Initial conc. at time zero ko: Zero-order rate constant t : Time Similarly, Equation can be expressed as Amount [A] instead of conc. (Also true for other reaction orders)
Can any weakly acidic molecule work as an enteric coating material?
The answer is no; there are requirements that we need to know: 1) For an acidic compound to serve as an enteric coating material, its neutral form should be insoluble in water. So, acids like citric, tartaric, and lactic acids will not work because their neutral forms are highly soluble in water. 2) The other essential requirement for an acidic compound to serve as enteric coating material has to do with its pKa. Knowing that the pH in the stomach when it has food is no more than 2 and the pH in the intestinal lumen is around 8.
The solubility of a drug is defined as...
The concentration of the drug when the solution is saturated or at equilibrium (i.e. when there is some solid left at the bottom of the container).
What do you think will happen if, for example, after lowering the pH to dissolve a basic drug, we added another ingredient that caused the pH to rise; What do you think will happen?
The dissolved drug will start to precipitate again because it will return to the neutral form which is not soluble. Precipitation in this case occurs because the reactions in figure 3 are reversible ones as the arrows show; if you are to reverse the conditions, both reactions will proceed backward regenerating the insoluble neutral form.
Salting in
This is when the solubility of a nonelectrolyte increases upon adding electrolytes to the solution, usually at low concentration. An example of salting in is protein and salt. Immunoglobulins proteins of the immune system used in vaccines to protect us from different pathogens. Immunoglobulins are large and complex proteins that are poorly soluble in water but in order for them to be injected into the blood stream, they need to be in solution. The solubility of immunoglobulins and other proteins increases upon adding a small amount of salt into the solution.
Shelf-Life:
Time required for 10% of the material to disappear; it is the time at which C (or A) has decreased to 90% of its original value, 0.9 C (or 0.9 A).
Half Life:
Time required for one-half of the material to disappear; it is the time at which C (or A) has decreased to 1⁄2 C (or 1⁄2 A).
T/F: The amorphous form is usually more soluble than the crystalline one.
True
T/F: You can always assume "b" is equal to 1 unless told otherwise.
True
T/F: concentrations will be in molarity; if given in any other expression we need to convert to molarity before using the equation.
True
TRUE or FALSE: The great majority of drugs currently on the market have their Po/w values range between 10 and 1000.
True
[BLANK] (such as sodium bicarbonate) will raise urine pH to above 7 whereas [BLANK] (such as potassium dihydrogen phosphate) will decrease urine pH to less than 7.
Urine alkalinizers, urine acidifiers
The buffering capacity should be between 0.01 to 0.1, which is not high. This is to allow the body to...
adjust the pH quickly if there were errors in making the solution and the pH is not what it should be.
What are the strong bases?
all metal hydroxides are strong; e.g. sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, ..... and so on. All other bases are weak
Fluorophores are usually...
aromatic flat groups with lone pairs.
When it comes to preserving emulsion, the minimum inhibitory concentration of a weak acid preservative is defined...
as the lowest concentration of the neutral form of the acidic preservative that need to be present in the aqueous phase to prevent microbial growth.
Thimerosal is an organic mercury preservative that is added to the multi-dose vials of flu vaccines to prevent the growth of germs that can contaminate them. Because of the high toxicity of mercury, its level in those vaccines has to be tightly regulated. Which of the following spectroscopic techniques can be used to determine the amount of mercury in flu vaccines? a. IR spectroscopy b. Atomic absorption spectroscopy c. UV-Vis spectroscopy d. Determine degree of rotation of polarized light
b. Atomic absorption spectroscopy In determining concentrations of elements, atomic absorption spectroscopy is the most suited technique. IR is for structural determinations only. Both UV-Vis absorption and degree of rotations are quantitative techniques but they can not detect mercury. Mercury can absorb UV light but its absorption peak will be masked by the other functional groups in the compound which will make quantitative determinations inaccurate. In addition, mercury does not rotate plane polarized light.
A pharmaceutical product contains a liquid ingredient; liquid X whose vapor pressure = 0.0001 atm. Knowing that the vapor pressure of water is 0.03 atm, which of the following may be true about liquid X? a. Liquid X has more or less the same molecular weight as water and just as polar as water b. Liquid X is a highly polar compound with a molecular weight a lot higher than that of water c. Liquid X is a totally non-polar liquid that has a molecular weight much less than that of water
b. Liquid X is a highly polar compound with a molecular weight a lot higher than that of water
Highly volatile liquids have high vapor pressure but low...
boiling points.
From the group of words below, select the group of words that best complete this sentence: UV light destroys _______________ molecules causing ____________________. a. vitamins and hemoglobin skin redness and anemia b. cell membranes hemolysis and skin rash c. DNA and collagen skin cancer and wrinkling d. nuclei and mitochondria skin wrinkling and itching e. hemoglobin and cytochromes skin paling and itching
c. DNA and collagen skin cancer and wrinkling
Ritonavir, the active ingredient in Norvir(R), is an anti-HIV drug launched in 1996. After the product had been distributed for about 18 months without trouble, the manufacturing company observed an unexpected occurrence. The final product did not show dissolution in water and the drug was precipitating. Which of the following best explains this unexpected occurrence and what would be your recommendation to the manufacturer to avoid this problem in the future? a. Ritonavir must be an amorphous drug. The manufacturer should always use the crystalline form of the drug because it is the most soluble b. Ritonavir must be a polymorphic drug and it converts to an insoluble form upon storage. The manufacturer should only make it in tablet form because insolubility does not affect absorption c. Ritonavir is a polymorphic drug with one or more insoluble crystal forms. The manufacturer should identify the most soluble form of ritonavir and should always use it in making tablets d. Ritonavir is a non-polar drug. The manufacturer should prepare it in oral solution form using a non-polar solvent like hexane or chloroform, not water
c. Ritonavir is a polymorphic drug with one or more insoluble crystal forms. The manufacturer should identify the most soluble form of ritonavir and should always use it in making tablets
Strong acids and bases [BLANK] dissociate in water to release all their H+ or OH-; respectively.
completely
Human plasma contains about 5 mEq/L of Ca++. How many milligrams of calcium chloride dihydrate (CaCl2•2H2O, mol. Wt. = 147 g/mol) are required to prepare 750 mL of a solution equal in Ca++ to human plasma? a. 735mg. b. 551mg. c. 0.276mg. d. 276mg. e. 0.735mg.
d. 276mg For this question, we need to prepare 750 mL of a solution that is 5mEq/L in Ca++ The source of Ca++ we have is CaCl2•H2O. Because we'll be using CaCl2• 2H2O for its Ca++ content, its equivalent weight = mol wt / 2 (because calcium loses 2 electrons) = 147/2 = 73.5 g / Eq This means that 1 Eq of CaCl2• 2H2O weighs 73.5 g and 0.005 Eq will weigh X X = 73.5 × 0.005 = 0.3675 g To prepare 1 L, we use 0.3675 g To prepare 0.75 L, we use X X = 0.367 × 0.75 = 0.2756 g So, to prepare 750 mL 5 mEq Ca++ solution using CaCl2• 2H2O we dissolve 0.276 g in enough pure water to a final volume 750 mL.
We use Beer's law to...
determine concentrations of unknown solutions.
In order for a molecule to dissolve in water, it has to have polar groups that allow it to form [BLANK] and/or [BLANK] interactions. The more favorable interactions a molecule can form with water, the more soluble it is. In addition, the more hydrophobic groups a molecule can have, the less soluble it becomes.
dipole-dipole, hydrogen bonding
Enteric coated medications are solid dosage forms (like tablets and capsules) that, when taken orally...
do not open up nor release their contents in the stomach. Enteric coated medications release their active ingredients in the intestine. That way, patients can take their daily fish oil dose without experiencing the unpleasant fishy reflux.
Sunscreens must have [BLANK] bonds as well.
double
UVB because it has more [BLANK] and, therefore, is more responsible for photoagaing and skin cancer.
energy
Which of the following you expect to be most effective in dissolving iodine (molecular formula is I-I) in water (molecular formula H - O - H)? O || a. CH3 - C - CH3 b. CH3 - CH2 - O - CH3 c. I- d. Na+ e. a and b f. c and d
f. c and d Both the iodide anion or the sodium cation will work because the electric field around an ion (whether a cation or an anion) is strong and more capable of shifting the electron cloud around the non-polar iodine molecule than dipoles (i.e. the ketone in "a" or the ether in "b").
Uncharged/neutral molecules are...
highly absorbed (i.e. 90% or more enter the cell by passive diffusion)
It is important here to emphasize that pH changes have...
no effect on the solubility of non-electrolyte molecules such as glucose, sucrose, and the steroid hormones.
Charged/polar molecules are...
poorly absorbed (i.e. 10% or less enter the cell by passive diffusion)
A cosolvent system containing water and organic solvents like alcohol and glycerol are both are [BLANK] for internal use.
safe
Whichever solvent you choose for your drug, make sure it is...
safe for human consumption, because if it is not, you will lose points. Most organic solvents are not safe for human use at all (e.g. benzene or n-hexane) or have undesirable effects such as diethyl ether (has an anesthetic effect).
Non-electrolytes do not ionize and, therefore, the pH will have no effect on their...
solubility or absorption properties.
Drugs are only absorbed from [BLANK] form.
solution That means that the solid drug has to dissolve in body fluids first in order to be absorbed and to produce an effect.
In applying Beer's law, we always take the absorbance of the solution at the wavelength where our compound absorbs maximally (λmax). If the wavelength corresponding to maximum absorbance of the compound is not known, we...
take an absorbance scan over a range of wavelength and record the absorbance at the highest point on the curve.
Borate buffers can not be used to buffer solutions for injection or for oral administration because...
they are toxic internally.
One of the important applications of cosolvency is...
to prepare solutions containing the neutral form of weak electrolytes. Weak electrolytes (i.e. weakly acidic/basic drugs) are drugs that can exist in a neutral and charged form.