Lowest molar mass carbonate yields greatest CO2 loss

Steps:

• Carbonates decompose: MCO3 → MO + CO2; mass loss equals CO2 mass.
• Moles of carbonate in 4.0 g = 4.0 / molar mass of MCO3.
• Mass of CO2 = moles × 44 g/mol.
• Smallest molar mass gives most moles, thus most CO2 and greatest loss.

Why C is correct:

• Lithium carbonate (Li2CO3) has lowest molar mass (74 g/mol), maximizing moles and CO2 release per 4.0 g.

Why the others are wrong:

• A: BaCO3 (197 g/mol) has high molar mass, minimizing moles and CO2.
• B: CuCO3 (124 g/mol) has higher molar mass than Li2CO3, reducing CO2 loss.
• D: MgCO3 (84 g/mol) has higher molar mass than Li2CO3, yielding less CO2.

Final answer: C