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JAMB Chemistry 2002 Question 20

Question 20

Volumetric Analysis

25cm3 of a 0.2 mol dm−3 solution of Na2CO3 requires 20cm3 of a solution of HCl for neutralization. The concentration of the HCl solution is

  1. A.0.5 mol dm−3
  2. B.0.6 mol dm−3
  3. C.0.2 mol dm−3
  4. D.0.4 mol dm−3
Show the answer and explanation

Answer: A (0.5 mol dm−3)

Explanation

Na2CO3 + 2HCl → 2NaCl + H2O + CO2. Moles of Na2CO3 = 0.2 × 0.025 = 0.005, so HCl = 0.010 mol in 0.020 dm3 = 0.5 mol dm−3.