Question

question 3 (3 points)
120 g of a compounded ointment contains 350 mg of neomycin sulfate. what is the percent strength of the ointment?
question 4 (3 points)
if 75 g of active ingredient powder is mixed with 400 ml ns solution, what is the final concentration? round to the nearest hundredths (w/v).

Explanation:

Question 3

Step1: Convert units to be consistent

We know that \(1\space g = 1000\space mg\), so \(350\space mg=\frac{350}{1000}\space g = 0.35\space g\). The total weight of the ointment is \(120\space g\).

Step2: Calculate percent strength

Percent strength (\(w/w\)) is given by the formula \(\text{Percent Strength}=\frac{\text{Weight of solute}}{\text{Weight of solution}}\times100\%\). Substituting the values, we get \(\text{Percent Strength}=\frac{0.35}{120}\times100\%\).

Step3: Compute the value

\(\frac{0.35}{120}\times100\%=\frac{0.35\times100}{120}\%=\frac{35}{120}\%\approx0.29\%\)

Step1: Recall the formula for (w/v) concentration

The formula for weight - volume (\(w/v\)) concentration is \(\text{Concentration}=\frac{\text{Weight of solute (g)}}{\text{Volume of solution (mL)}}\times100\%\) (when expressing as a percentage) or just \(\frac{\text{Weight of solute (g)}}{\text{Volume of solution (mL)}}\) for the concentration in \(g/mL\) (and then we can convert to percentage if needed, but here we are asked for \(w/v\) concentration which is \(\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\times100\%\) in percentage terms or \(\frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}}\) in \(g/mL\) with percentage implied).

Step2: Substitute the values

We have the mass of the active ingredient (solute) \(m = 75\space g\) and the volume of the NS solution (solvent, and the final volume of the solution is approximately the volume of the solvent since we are adding powder which has negligible volume compared to the solution) \(V = 400\space mL\). So the concentration \(C=\frac{75}{400}\times100\%\) (for percentage) or \(C = \frac{75}{400}\space g/mL\) (and then we can calculate the percentage).

Step3: Calculate the concentration

\(\frac{75}{400}\times100\%=\frac{75\times100}{400}\%=\frac{7500}{400}\% = 18.75\%\) (in percentage terms for \(w/v\)) or \(\frac{75}{400}=0.1875\space g/mL\approx0.19\space g/mL\) (when rounded to the nearest hundredths). But since \(w/v\) concentration is often expressed as a percentage, the concentration is \(18.75\%\) or \(0.19\space g/mL\) (depending on the interpretation, but since it's \(w/v\) and we have \(75\space g\) in \(400\space mL\), \(\frac{75}{400}=0.1875\approx0.19\) when rounded to the nearest hundredths).

Answer:

The percent strength of the ointment is approximately \(0.29\%\)

Question 4