A hospital saline solution is analyzed to verify its concentration. A \(50.0-\mathrm{mL}\) sample of the solution with a mass of \(50.320 \mathrm{~g}\) is evaporated to dryness. If the solid sodium chloride residue has a mass of \(3.84 \mathrm{~g}\), what was the mass percent of sodium chloride in the original solution?

When it comes to preparing solutions in a clinical setting, accuracy is key. Saline solutions, for instance, are commonly used in hospitals and need to be precisely prepared to ensure patient safety. Concentration refers to the amount of solute dissolved in a solvent. In the context of a saline solution, the solute is sodium chloride (salt), and the solvent is water. The concentration is often expressed as a mass percent, which indicates the mass of the solute compared to the total mass of the solution.

A mass percent is calculated using the formula:
\[ \text{Mass percent} = \left( \frac{\text{Mass of solute}}{\text{Total mass of solution}} \right) \times 100\% \]

Understanding how to calculate the mass percent is vital for healthcare professionals to administer the correct dosage of saline to patients. In the example provided, where the solid sodium chloride residue is 3.84 g from a 50 mL solution with an original mass of 50.320 g, the mass percent tells us the strength of the saline solution, which is essential information for medical applications.

Evaporation to dryness is a common laboratory technique used to separate a solvent from a solute. This method relies on heating the solution until the solvent completely evaporates, leaving behind the solid residue of the solute. In many analytical procedures, this technique is key to determining the concentration of a solution. When performing evaporation, it's crucial to apply steady heat and ensure that all of the solvent has been removed to accurately measure the mass of the residue.

During the process, you may encounter challenges such as splattering, which can lead to loss of the solute and inaccurate results. To prevent this, the solution should be heated gently, and protective measures, such as a watch glass, could be used to cover the container. The end goal is to obtain the dry residue, which, when weighed, can provide the data needed for calculations like finding the mass percent concentration of a saline solution. In our exercise, evaporation to dryness was used to determine the mass of sodium chloride present in the original saline solution.

After the evaporation method is performed, the remaining solid is known as residue. In the context of our example, the residue consists of sodium chloride crystals that were initially dissolved in the water. The mass of this residue is essential for calculating the mass percent concentration of the saline solution. Care must be taken to ensure that the residue is free from contaminants and completely dry, as excess water or other substances will skew the results.

Measuring the sodium chloride residue accurately requires precise weighing on a laboratory balance. In practical situations, the residue might also be used for further testing or analysis. For instance, if the purity of the sodium chloride needs to be verified, additional chemical testing might follow. However, in our exercise, the sole purpose of obtaining the sodium chloride residue's weight was to assist in the calculation of mass percent concentration of the saline solution.