In Trinidad, limestone (calcium carbonate) is quarried and reacts with hydrochloric acid according to the equation: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g). A student used 50 cm³ of 2.0 mol/dm³ HCl and excess limestone chips. How many moles of HCl were used?

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Question

In Trinidad, limestone (calcium carbonate) is quarried and reacts with hydrochloric acid according to the equation: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g). A student used 50 cm³ of 2.0 mol/dm³ HCl and excess limestone chips. How many moles of HCl were used?

Accepted Answer

0.10 mol — 10 mol. Award 1 mark for C. Number of moles = concentration × volume (in dm³). Moles = 2.0 mol/dm³ × (50/1000) dm³ = 2.0 × 0.05 = 0.10 mol. A is incorrect — divides by 2 incorrectly. B is incorrect — uses concentration of 1.0 instead of 2.0. D is incorrect — multiplies instead of converting cm³ to dm³.

Answer

0.025 mol

Answer

0.05 mol

Answer

0.20 mol

Answer

0.10 mol

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