In a titration 25.0 cm³ of hydrochloric acid is neutralised by 20.0 cm³ of 0.100 mol/l sodium hydroxide (HCl + NaOH → NaCl + H₂O). What is the concentration of the acid?
Answer and explanation
Correct answer: C. 0.0800 mol/l
- Step 1: Moles of NaOH = 0.100 × 0.0200 = 0.00200 mol.
- Step 2: The ratio is 1 : 1, so moles of HCl = 0.00200 mol.
- Step 3: Concentration = 0.00200 ÷ 0.0250 = 0.0800 mol/l.
Answer
0.0800 mol/l.
Why not the others: 0.125 mol/l: the volumes were inverted. 0.100 mol/l: the volumes were ignored. 0.00200 mol/l: the moles of NaOH were not divided by the acid volume.
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