Question

question 6 (5 points)
a physician orders 5 ml of epinephrine 1% added to 45 ml of sterile water to prepare 50 ml of solution.
what is the weight in milligrams of the epinephrine that has been added?
question 7 (3 points)
you receive an order for 125 ml of 4% acetic acid solution, and you have in stock 75% acetic acid solution.
how many ml of the 75% solution will you need? (you must round to the nearest tenths.)

Explanation:

Question 6

Step1: Recall percentage concentration

A 1% solution means 1 gram per 100 mL (or 10 mg per mL, since 1 gram = 1000 mg, so $\frac{1000\ \text{mg}}{100\ \text{mL}} = 10\ \text{mg/mL}$ for 1% solution? Wait, no: 1% w/v means 1 g per 100 mL. So 1% = 1 g/100 mL = 10 mg/mL (since 1 g = 1000 mg, so 1000 mg / 100 mL = 10 mg/mL). Wait, actually, 1% w/v is 1 gram of solute per 100 mL of solution. So for 5 mL of 1% epinephrine:

Step2: Calculate mass of epinephrine

First, find the concentration in mg/mL. 1% w/v = 1 g/100 mL = 1000 mg/100 mL = 10 mg/mL. Then, for 5 mL of this solution, mass = volume × concentration. So mass = $5\ \text{mL} \times 10\ \text{mg/mL} = 50\ \text{mg}$. Wait, let's check again: 1% w/v is 1 g per 100 mL, so per mL, it's 0.01 g/mL = 10 mg/mL. So 5 mL × 10 mg/mL = 50 mg.

Step1: Use dilution formula

The dilution formula is $C_1V_1 = C_2V_2$, where $C_1$ is the concentration of the stock solution, $V_1$ is the volume of stock needed, $C_2$ is the concentration of the desired solution, and $V_2$ is the volume of the desired solution.

Here, $C_1 = 75\%$, $C_2 = 4\%$, $V_2 = 125\ \text{mL}$. We need to find $V_1$.

Step2: Rearrange formula and solve

Rearranging the formula: $V_1 = \frac{C_2V_2}{C_1}$. Plugging in the values: $V_1 = \frac{4\% \times 125\ \text{mL}}{75\%}$. Calculate numerator: $4\% \times 125 = 5$ (since 0.04 × 125 = 5). Then divide by 75% (0.75): $V_1 = \frac{5}{0.75} \approx 6.7\ \text{mL}$ (rounded to the nearest tenth).

Answer:

50

Question 7