Glucose has a specific rotation of +52.8°. Predict the concentration of a glucose aqueous solution contained in a 10 cm long polarimetry tube if a rotation of +15.8° was observed.
A) 0.299 g/mL
B) 0299 g/mL
C) 3.34 g/mL
D) 334 g/mL

Question

Quizplus · Accepted Answer

The specific rotation $[\alpha]$ of a substance is related to the observed rotation $\alpha$, the concentration $c$ in grams per milliliter (g/mL), and the path length $l$ in decimeters (dm) by the formula $[\alpha] = \frac{\alpha}{l \cdot c}$. Given $[\alpha] = +52.8°$, $\alpha = +15.8°$, and $l = 10 cm = 1 dm$, we can solve for $c$: $c = \frac{\alpha}{[\alpha] \cdot l} = \frac{15.8}{52.8 \cdot 1} = 0.299 g/mL$.

Glucose Has a Specific Rotation of +52