25 cm of 1 mol/dm hydrochloric acid is diluted with water to a total volume of 1000 cm. What is the new concentration?

Answer and explanation

Correct answer: B. 0.025 mol/dm

  1. Step 1: The amount of acid is unchanged: .
  2. Step 2: mol/dm.
Answer
0.025 mol/dm.
Why not the others: 40 mol/dm: it inverts the volume ratio. 0.001 mol/dm: it ignores the original volume. 0.975 mol/dm: it uses the volume of water added instead of the original volume.

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25 cm 3 of 1 mol/dm 3… | HKDSE (Hong Kong) Mole Calculations