Explain5 marksStandard
A student wants to estimate the concentration of reducing sugars in an unknown solution. They first prepare standard glucose solutions of known concentrations: 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 g dm⁻³. To each standard they add 2 cm³ of Benedict's reagent and heat the mixture in a boiling water bath. They record the time taken for the first visible colour change from blue to green. The results are shown in the table.
| Glucose concentration / g dm⁻³ | Time for first colour change / s |
|---|---|
| 0.0 | No change after 600 s |
| 0.2 | 120 |
| 0.4 | 90 |
| 0.6 | 60 |
| 0.8 | 45 |
| 1.0 | 30 |
The student then tests the unknown solution under identical conditions and observes that it takes 50 seconds for the first colour change.
Explain how the student can use these results to estimate the concentration of reducing sugars in the unknown solution.