2018 · Q1
Two reactants in a flask at room temperature are producing bubbles of a gas that turn limewater milky. The reactants could be
General KnowledgeChemistry
- Azinc and hydrochloric acid
- Bmagnesium carbonate and hydrochloric acid
- Cmethane and oxygen
- Dcopper and dilute hydrochloric acid
Explanation
Carbon dioxide is the gas that turns limewater milky, because Ca(OH)2 reacts with CO2 to form insoluble white calcium carbonate (CaCO3). Magnesium carbonate reacts with hydrochloric acid at room temperature to release CO2 (MgCO3 + 2HCl -> MgCl2 + H2O + CO2), producing the observed bubbles. Zinc with hydrochloric acid releases hydrogen, which does not affect limewater. Copper does not react with dilute hydrochloric acid at all, and methane needs ignition to burn, so neither fits the room-temperature observation.