25.0 cm cubed of sodium hydroxide solution is neutralised by 20.0 cm cubed of 0.10 mol/dm cubed hydrochloric acid. The reaction is 1 : 1. What is the concentration of the sodium hydroxide?
Answer and explanation
Correct answer: C. 0.080 mol/dm cubed
- Step 1: Moles of HCl = 0.10 x (20.0 / 1000) = 0.0020 mol.
- Step 2: The ratio is 1 : 1, so NaOH is also 0.0020 mol.
- Step 3: Concentration = 0.0020 / (25.0 / 1000) = 0.080 mol/dm cubed.
Answer
0.080 mol/dm cubed.
Why not the others: 0.125 divides the volumes the wrong way up, 0.10 ignores the different volumes and 0.0020 is the number of moles, not the concentration.
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