The doctor orders a $14 \frac{1}{2} \%$ solution. He asks the pharmacy to prepare $35 \mathrm{~mL}$ of the solution. How many grams of pure drug will be in $35 \mathrm{~mL}$ of this $14 \frac{1}{2} \%$ solution? Round to the nearest tenth.

Step 1 ：Given that the doctor orders a $14 \frac{1}{2} \%$ solution and asks the pharmacy to prepare $35 \mathrm{~mL}$ of the solution.

Step 2 ：We are asked to find how many grams of pure drug will be in $35 \mathrm{~mL}$ of this $14 \frac{1}{2} \%$ solution.

Step 3 ：To find the amount of pure drug, we need to multiply the total volume of the solution by the percentage of pure drug.

Step 4 ：Let's denote the total volume as \(total\_volume = 35\)

Step 5 ：The percentage of pure drug is \(percentage\_pure\_drug = 14.5\)

Step 6 ：We convert the percentage to decimal form: \(percentage\_pure\_drug\_decimal = 0.145\)

Step 7 ：We calculate the amount of pure drug: \(pure\_drug = total\_volume \times percentage\_pure\_drug\_decimal = 5.074999999999999\)

Step 8 ：We round the result to the nearest tenth: \(pure\_drug\_rounded = 5.1\)

Step 9 ：Final Answer: The amount of pure drug in the solution is \(\boxed{5.1}\) grams.