Explain6 marksChallenge
A student carries out a semi-quantitative Benedict's test to estimate the concentration of reducing sugar in an unknown solution. They first prepare a set of glucose standards with known concentrations (g dm⁻³) and record the colour produced after heating for exactly 5 minutes with Benedict's solution:
| Glucose concentration (g dm⁻³) | Colour after 5 min |
|---|---|
| 0 | Blue (unchanged) |
| 10 | Green |
| 20 | Yellow |
| 40 | Orange |
| 80 | Red |
The unknown solution gives a colour between yellow and orange. The student suspects the unknown may also contain a non‑reducing sugar.
Explain how the student can use this standardised Benedict's test to estimate the concentration of reducing sugar in the unknown, and describe what additional steps are needed if non‑reducing sugars are present.