Other alkaline solutions
2 marks · EasyA student dissolves 0.20 mol of sodium carbonate (Na_2CO_3) in enough water to make 1.0 dm³ of solution. Sodium carbonate forms an alkaline solution because it reacts to produce hydroxide ions.
Calculate the concentration of carbonate ions (CO_3^{2-}) present in the solution. Give your answer in mol/dm³.
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0.20 mol/dm³ (±0.01)
Common mistakes: Dividing by 2 instead of 1.0; Confusing carbonate ions with sodium ions
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Marking points
M1 · 1 mark · Correct method for finding concentration by dividing moles by volume (in dm³).
A1 · 1 mark · Correct final answer of 0.20 mol/dm³ given, with correct unit.
Worked solution
The number of moles of carbonate ions is 0.20 mol.
The solution volume is 1.0 dm³.