The student recorded the following data.
| \( Na_2S_2O_3 \) concentration (\( mol \, dm^{-3} \)) | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Trial 5 | Average |
|—|—|—|—|—|—|—|
| \( 0.1500 \pm 0.08\% \) | 21.1 | 19.7 | 18.1 | 17.3 | 19.4 | \( 19.1 \pm 1.5 \) |
| \( 0.120 \pm 0.1\% \) | 26.4 | 24.8 | 26.9 | 26.2 | 25.1 | \( 25.9 \pm 0.9 \) |
| \( 0.0900 \pm 0.1\% \) | 33.8 | 32.4 | 31.5 | 30.8 | 32.6 | \( 32.2 \pm 1.2 \) |
| \( 0.0600 \pm 0.2\% \) | 48.3 | 49.3 | 45.9 | 46.4 | 44.6 | \( 46.9 \pm 1.9 \) |
| \( 0.0300 \pm 0.4\% \) | 96.2 | 95.8 | 97.9 | 95.9 | 93.7 | \( 95.9 \pm 1.0 \) |
The solutions of sodium thiosulfate were in fact, all made as accurately as possible from the solid sodium thiosulfate by weighing the appropriate mass with a balance that can measure to one hundredth of a gram (\( \pm 0.01 \, g \)), rather than by dilution of a stock solution.
Explain why the percent uncertainties of concentrations increase as the concentrations decrease.