CSMLS Practice Exam 2025 – All-in-One Guide to Mastering Medical Laboratory Science Certification

To determine the amount of sodium chloride needed to make a 5% solution, it is important to understand what a 5% solution indicates. A 5% (w/v) solution means that there are 5 grams of solute (in this case, sodium chloride) for every 100 milliliters of solution.

To calculate how much sodium chloride is required for 300 milliliters of this solution, you can use the following steps:

1. Start with the definition of a 5% solution: 5 grams per 100 mL.

2. Since you want to prepare a total of 300 mL, you will multiply the amount of sodium chloride needed for 100 mL by 3 (because 300 mL is three times 100 mL).

Calculating this gives:

\[

5 \, \text{g} \times 3 = 15 \, \text{g}

\]

Thus, to prepare 300 mL of a 5% sodium chloride solution, 15 grams of sodium chloride is required. This aligns with the calculation and confirms that the answer is correct. The other choices represent incorrect amounts based on miscalculations of the concentration or volume.