Cao Practice Quiz: Lec3 solutions II-III: PCEUT 531 A Au 26: Pharmaceutical Formulation: Principles And Dosage Forms

Based on the formal stoichiometry $K_3PO_4 \rightarrow 3\,K^+ + PO_4^{3-}$, what are the potassium and phosphate charge-amount magnitudes corresponding to $2.00\,\text{mmol}$ of $K_3PO_4$?

$6.00\,\text{mEq}\,K^+$ and $6.00\,\text{mEq}\,PO_4^{3-}$

True or False: To obtain a salt charge factor $n$, add the magnitudes of its total positive and total negative charges together.

False (the charge factor $n$ is the total magnitude of positive charge or the total magnitude of negative charge per formula unit, not their sum).

A solution contains $9.53\,\text{g}$ of anhydrous $MgCl_2$ in a final volume of $250\,\text{mL}$. Using $MW = 95.3\,\text{g/mol}$, what is its normality with respect to $Mg^{2+}$ charge?

$$0.800\,\text{Eq/L}$$

How many equivalents ($\text{Eq}$) of $Mg^{2+}$ are contained in $9.53\,\text{g}$ of anhydrous $MgCl_2$ ($MW = 95.3\,\text{g/mol}$)?

$0.200\,\text{Eq}$ (calculated from $0.100\,\text{mol} \times 2$ charge valence)

How many milliequivalents of $Na^+$ are present in $8.0\,\text{mL}$ of a $20\%\,\text{w/v}$ trisodium citrate dihydrate solution ($Na_3C_6H_5O_7\cdot 2H_2O$, $MW = 294\,\text{g/mol}$)?

$$16.3\,\text{mEq}$$

What mass of solute is contained in $8.0\,\text{mL}$ of a $20\%\,\text{w/v}$ solution of trisodium citrate dihydrate?

$1.6\,\text{g}$ ($8.0\,\text{mL} \times 0.20\,\text{g/mL}$)

What mass of $K_3PO_4$ ($MW = 212\,\text{g/mol}$) is required to prepare a final volume of $250\,\text{mL}$ containing a total of $60.0\,\text{mEq}$ of $K^+$?

$$4.24\,\text{g}$$

How many millimoles of $K_3PO_4$ are required to yield $60.0\,\text{mEq}$ of $K^+$?

$20.0\,\text{mmol}$ (since each formula unit of $K_3PO_4$ releases $3\,K^+$ ions)

Which of the following groups is a usual hydrogen-bond donor to water: an ether group ($R\text{-}O\text{-}R$), a hydroxyl group ($R\text{-}O\text{-}H$), a ketone carbonyl group ($R\text{-}C(=O)\text{-}R$), or a hydrocarbon group ($R\text{-}CH_2\text{-}R$)?

A hydroxyl group, $R\text{-}O\text{-}H$

Why can ether ($R\text{-}O\text{-}R$) and ketone carbonyl ($R\text{-}C(=O)\text{-}R$) functional groups act as hydrogen-bond acceptors but not hydrogen-bond donors to water?

They contain electronegative oxygen atoms with lone pairs, but lack hydrogen atoms directly bonded to electronegative atoms.

True or False: During hydration, the oxygen end of a water molecule preferentially faces an anion.

False (the partially positive hydrogen atoms preferentially face an anion).

Which atom of a water dipole molecule preferentially faces a cation during ion hydration in solution?

The oxygen atom (due to its partial negative charge)

At equilibrium, a neutral drug has a concentration of $20.0\,\mu\text{g/mL}$ in octanol and $0.200\,\mu\text{g/mL}$ in water. What is its $\log(P)$?

$$2$$

What is the partition coefficient $P$ when the equilibrium concentration of a neutral drug is $20.0\,\mu\text{g/mL}$ in octanol and $0.200\,\mu\text{g/mL}$ in water?

$P = 100$ ($\frac{20.0\,\mu\text{g/mL}}{0.200\,\mu\text{g/mL}} = 100$)

A weak base has $pK_a = 8.0$. Assuming the ideal ionization model and acceptable drug stability, which comparison between $pH = 6.0$ and $pH = 10.0$ is usually correct?

At $pH = 6.0$, the drug is more ionized and usually has higher total aqueous solubility.

For a weak base with $pK_a = 8.0$, what is its predominant ionization state at $pH = 6.0$ compared to $pH = 10.0$?

At $pH = 6.0$ ($pH < pK_a$), it is predominantly ionized (protonated), whereas at $pH = 10.0$ ($pH > pK_a$), it is predominantly un-ionized.

Using the approximate volume-weighted model, calculate the relative dielectric constant of a nominal mixture containing $30\%\,\text{v/v}$ ethanol ($\epsilon = 25$) and $70\%\,\text{v/v}$ water ($\epsilon = 80$).

$63.5$ ($0.30 \times 25 + 0.70 \times 80 = 7.5 + 56 = 63.5$)

What mathematical formula represents the approximate volume-weighted model for the relative dielectric constant ($\epsilon_{\text{mix}}$) of a binary solvent system?

$\epsilon_{\text{mix}} = f_1 \epsilon_1 + f_2 \epsilon_2$, where $f_1$ and $f_2$ are the volume fractions of the components.

At the stated conditions, polymorph A is the stable crystal form and polymorph B is metastable. Which comparison best describes polymorph B relative to A?

Polymorph B has higher free energy and often higher solubility than polymorph A.

Why does a metastable crystal polymorph typically possess higher aqueous solubility than its stable crystal polymorph?

It possesses a higher thermodynamic free energy state, meaning less energy is required to break the crystal lattice during dissolution.

True or False: A higher $\log(P)$ always guarantees better oral absorption.

False

True or False: Adding an electrolyte can reduce another solute's aqueous solubility, and the effect depends on the particular salt and solute.

True

What phenomenon occurs when the addition of an electrolyte decreases the aqueous solubility of a non-electrolyte solute?

Salting out (the electrolyte ions tie up water molecules in hydration shells, reducing available free water for solute dissolution).

True or False: Two cosolvent vehicles with similar relative dielectric constants must provide the same drug solubility.

False

In the complete dissociation of $1\,\text{mol}$ of a neutral salt, why do the total positive charge and total negative charge magnitudes match?

Because the dissociation must maintain electroneutrality, resulting in identical total equivalents of positive and negative charges.