A student performs a gravimetric analysis to determine the mass percent of \(\text{BaCl}_2\) in a solid mixture containing \(\text{BaCl}_2\) and \(\text{NaCl}\). The student dissolves a \(1.250 \text{ g}\) sample of the mixture completely in distilled water and adds an excess of \(0.50 \text{ M } \text{Na}_2\text{SO}_4\text{(aq)}\) to precipitate \(\text{BaSO}_4\text{(s)}\), as represented by the net ionic equation below.

\[ \text{Ba}^{2+}\text{(aq)} + \text{SO}_4^{2-}\text{(aq)} \rightarrow \text{BaSO}_4\text{(s)} \]

The precipitate is collected on filter paper, but the student fails to rinse the collected solid with distilled water before placing it in an oven to dry. After drying the sample to a constant mass, the student uses the measured mass of the dry solid to calculate the mass percent of \(\text{BaCl}_2\) in the original mixture.

Which of the following correctly predicts the effect of this error on the calculated mass percent of \(\text{BaCl}_2\), and provides the correct justification?