1)
bubbles of colourless and odourless gas
2)spontaneous reaction with effervescence
.
Sodium carbonate on reacting with acetic acid forms sodium acetate and releases carbon dioxide in the process, which is a colourless and odourless gas.
Both solid sodium carbonate and its aqueous solution will react with acetic acid.
Following is the chemical equation for the reaction
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2