Acid-carbonate salt formation Steps:

• Recognize propanoic acid as RCOOH (R=CH3CH2), but choices use CH3COOH analogously.
• Recall general reaction: 2RCOOH + CaCO3 → (RCOO)2Ca + CO2 + H2O.
• Balance equation: 2 acids neutralize carbonate, yielding salt, CO2 gas, and water.
• Compare choices to match reactants (CaCO3) and products (salt, CO2, H2O).

Why C is correct:

• Matches acid-carbonate reaction formula, producing calcium propanoate (as (CH3COO)2Ca analog), CO2, and H2O per standard neutralization.

Why the others are wrong:

• A: Wrong salt formula (2CH3COOCa) and unbalanced; implies two separate salts.
• B: Uses CaO (oxide), not CaCO3 (carbonate), so no CO2 produced.
• D: Uses CaO but incorrectly includes CO2, which oxide reactions do not generate.

Final answer: C