Chemistry · May / June 2026 · Paper 12 · Question 9
5070The mole and the Avogadro constant
During a titration, 25.0 cm$^3$ of 0.050 mol/dm$^3$ aqueous sodium hydroxide, NaOH, reacts exactly with 20.0 cm$^3$ of dilute phosphoric acid, H$_3$PO$_4$. 3NaOH + H$_3$PO$_4$ → Na$_3$PO$_4$ + 3H$_2$O What is the concentration of the dilute phosphoric acid?
- A0.0208 mol/dm$^3$
- B0.0313 mol/dm$^3$
- C0.0625 mol/dm$^3$
- D0.1875 mol/dm$^3$
As printed in the paper
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Correct answer: A. 0.0208 mol/dm$^3$
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