Q.(i) What is van't Hoff factor?

Using the first data point to find R, then applying $\pi = CRT$ again with the new osmotic pressure gives C ≈ 0.061 mol/L.

1. van't Hoff factor: $i = \dfrac{\text{observed (experimental) colligative property}}{\text{calculated (theoretical/normal) colligative property}} = \dfrac{\text{normal molar mass}}{\text{observed/abnormal molar mass}}$ It measures the deviation of a solute's actual colligative behaviour from ideal (non-dissociating, non-associating) behaviour: $i > 1$ for dissociating solutes (electrolytes), $i < 1$ for associating solutes, and $i = 1$ for an ideal non-electrolyte like glucose.
2. Finding the new molar concentration: Given: 36 g glucose per litre, $\pi_1 = 4.98$ bar at $T = 300$ K, molar mass of glucose $= 180$ g mol$^{-1}$. Concentration: $C_1 = \dfrac{36}{180} = 0.2$ mol L$^{-1}$. Since glucose is a non-electrolyte ($i=1$), $\pi = CRT$: …