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In the old vinegar test, potassium carbonate was added until bubbling stopped. What gas caused the bubbling?
AHydrogen gas
BOxygen gas
CAmmonia gas
DCarbon dioxide
Answer & Solution
Correct answer: D. Carbon dioxide
1. Vinegar owes its taste and smell mainly to acetic acid.
2. Acetic acid reacts with potassium carbonate to give potassium acetate, water and a gas.
3. That gas is carbon dioxide, and it caused the effervescence observed.
4. When bubbling stopped, all the acid had reacted, which marked the end point.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.5 Quantitative Chemical Analysis_
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