To determine the mass of Calcium ion in a Calcium-enriched tablet, we first add

Question

To determine the mass of Calcium ion in a Calcium-enriched tablet, we first add excess amount of HCl to dissolve the tablet, then add sodium carbonate to re-precipitate Ca2+in the solution. Which chemical equation below describes the re-precipitation process of Ca2+?

2 HCl (aq) + Na2CO3 (aq) -> 2 NaCl (aq) + CO2 (g) + H2O (l)

HCl (aq) + Na2CO3 (aq) -> NaHCO3 (aq) + NaCl (aq)

CaCO3(s) + 2 HCl (aq) -> CaCl2 (aq) + CO2 (g) + H2O (l)

CaCl2 (aq) + Na2CO3 (aq) -> CaCO3 (s) + 2 NaCl (aq)

2 HCl (aq) + Na2CO3 (aq) -> 2 NaCl (aq) + CO2 (g) + H2O (l)

HCl (aq) + Na2CO3 (aq) -> NaHCO3 (aq) + NaCl (aq)

CaCO3(s) + 2 HCl (aq) -> CaCl2 (aq) + CO2 (g) + H2O (l)

CaCl2 (aq) + Na2CO3 (aq) -> CaCO3 (s) + 2 NaCl (aq)

Explanation / Answer

Given

initially excess HCl is added to dissolve the tablet

So CaC03 reacts with HCl to given CaCl2 , C02 and H20

the reaction is given by

CaC03 (s) + 2HCl (aq) ----> CaCl2 (aq) + C02(g) + H20 (l)

now

given

sodium carbonate is added to re-precipitate Ca+2 in the solution

sodium carbonate is Na2C03

in the re-precipitation reaction

CaCl2 reacts with Na2C03 to give CaC03 and NaCl

so the reaction is given by

CaCl2 (aq) + Na2C03 (aq) ----> CaC03 (S) + 2 NaCl (aq)

From the given options

the correct answer is

option

D) CaCl2 (aq) + Na2CO3 (aq) -> CaCO3 (s) + 2 NaCl (aq)

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