Multiple choice

Which one of the following operations does not bring about a chemical change?

  1. Pressing dried up nitrogen tri-iodide.

  2. Mixing solid sodium bicarbonate with solid tartaric acid.

  3. Bringing phosphorus and oxygen in physical contact with each other.

  4. Passing electric current through acidified water.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Pressing nitrogen tri-iodide triggers its explosive decomposition (chemical change). Mixing solid NaHCO3 with solid tartaric acid causes no reaction without water, so this is the only physical change. Phosphorus spontaneously ignites in oxygen (combustion, chemical change). Electrolysis of acidified water decomposes it into H2 and O2 gases (chemical change).

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