100 cm^3 of 2 mol/dm^3 acid is diluted with water to 400 cm^3. What is the new concentration?
Answer and explanation
Correct answer: D. 0.5 mol/dm^3
- Step 1: The amount of solute is unchanged, so c1 V1 = c2 V2.
- Step 2: c2 = 2 x 100 / 400 = 0.5 mol/dm^3.
Answer
0.5 mol/dm^3.
Why not the others: '8 mol/dm^3' multiplies by the dilution factor instead of dividing; '1 mol/dm^3' assumes dilution always halves the concentration; '200 mol/dm^3' multiplies concentration and volume without dividing.
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