Two unknown elements and combine to form two distinct compounds, and . Stoichiometric data reveals t — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
Two unknown elements $A$ and $B$ combine to form two distinct compounds, $B_2A_3$ and $B_2A$. Stoichiometric data reveals that exactly $0.05\text{ moles}$ of $B_2A_3$ weigh $9.0\text{ g}$, and exactly $0.10\text{ moles}$ of $B_2A$ weigh $10.0\text{ g}$. Calculate the exact atomic weight of element $A$.
💡 Solution & Explanation
Let the atomic weights of A and B be $A$ and $B$ respectively. Step 1: Establish molar mass equations from the given data. For $B_2A_3$: Molar mass $= \frac{9.0\text{ g}}{0.05\text{ mol}} = 180\text{ g/mol} \implies 2B + 3A = 180$ (Eq 1). For $B_2A$: Molar mass $= \frac{10.0\text{ g}}{0.10\text{ mol}} = 100\text{ g/mol} \implies 2B + A = 100$ (Eq 2). Step 2: Solve the simultaneous equations. Subtract Eq 2 from Eq 1: $(2B + 3A) - (2B + A) = 180 - 100 \implies 2A = 80 \implies A = 40$. The atomic weight of element A is 40.