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Reviewed CSCA Chemistry question · Easy

In the laboratory, a colorless, odorless gas is generated by the reaction of a metal with dilute hydrochloric acid. A burning splint is extinguished when brought near the gas, but a pop sound is heard. Which gas is most likely produced?

  1. Oxygen
  2. Hydrogen
  3. Carbon dioxide
  4. Nitrogen
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Correct answer

B. Hydrogen

Principle or equation

Hydrogen gas is produced when certain metals react with dilute acids. It is colorless, odorless, and gives a characteristic 'pop' with a burning splint.

Why this answer is correct

The reaction of a metal with dilute HCl typically produces hydrogen gas. The pop sound is a classic test for hydrogen. Oxygen supports combustion, CO2 extinguishes without pop, and nitrogen is inert.

Example

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g). The gas collected gives a pop with a burning splint.

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