**Passage 7:** What is the mass of **free ** present in of oleum? — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

Reaction: $SO_3 + H_2O \rightarrow H_2SO_4$. <br>$1 \text{ mole } H_2O$ reacts with $1 \text{ mole } SO_3$. <br>$\text{moles } SO_3 = \text{moles } H_2O = 0.5$. <br>$\text{Mass } SO_3 = 0.5 \times 80 = 40 \text{ g}$.