Two reactants in a flask at room temperature are producing bubbles of a gas that turn limewater milky. The reactants could be
zinc and hydrochloric acid
magnesium carbonate and hydrochloric acid
methane and oxygen
copper and dilute hydrochloric acid
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC CDS-2 – 2018
Option A produces hydrogen gas (Zn + 2HCl → ZnCl₂ + H₂), which does not turn limewater milky.
Option C (methane and oxygen) is combustion, which doesn’t occur simply by mixing at room temperature and requires ignition.
Option D (copper and dilute hydrochloric acid) does not react as copper is less reactive than hydrogen.