A student passed the gas evolved from zinc and dilute acid into lime water. No milkiness appeared. What is the correct conclusion?
Answer and explanation
Correct answer: The gas is hydrogen, not carbon dioxide
Zinc is above hydrogen in the reactivity series, so with a suitable dilute acid it displaces hydrogen: Zn + 2HCl → ZnCl₂ + H₂. Carbon dioxide would turn lime water milky by forming calcium carbonate, but hydrogen does not. Thus the absence of milkiness supports hydrogen rather than CO₂; the other statements contradict the reaction or the limewater test. A burning-splint pop test can provide confirmation.
Frequently asked questions
What is the correct answer to this question?
The gas is hydrogen, not carbon dioxide
Why is this the correct answer?
Zinc is above hydrogen in the reactivity series, so with a suitable dilute acid it displaces hydrogen: Zn + 2HCl → ZnCl₂ + H₂. Carbon dioxide would turn lime water milky by forming calcium carbonate, but hydrogen does not. Thus the absence of milkiness supports hydrogen rather than CO₂; the other statements contradict the reaction or the limewater test. A burning-splint pop test can provide confirmation.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
