An excess of zinc carbonate was added to a 20.0 mL solution X that contains sulfide and thiosulfate ions. Reaction occured according to the net ionic equation below:

S2- + ZnCO3 → ZnS + CO32-

Upon completion of the reaction, the solution was filtered into a 50.0 mL volumetric flask and diluted to the mark.

20.0 mL of the diluted filtrate was then withdrawn and titrated with 5.20 mL of 0.01000 M standard solution of iodine.

What is the concentration (in molarity) of thiosulfate ion in the initial solution X.

0.0325M S₂O₃²⁻

Explanation:

Based on the reaction:

S²⁻ + ZnCO₃ → ZnS(s) + CO₃²⁻

1 mole of S²⁻ reacts per mole of ZnCO₃

when the reaction occurs, the sulfide ions are precipitated keeping in solution just S₂O₃²⁻ ions.

Then, these ions are titrated with iodine, thus:

2 S₂O₃²⁻ + I₂ → S₄O₆²⁻ + 2I⁻

That means 2 moles of thiosulfate react per mole of iodine.

Moles of iodine spent are:

5.20x10⁻³L ₓ (0.01000 mol / L) = 5.20x10⁻⁵ moles of I₂

5.20x10⁻⁵ moles of I₂ ₓ (2 moles S₂O₃²⁻ / 1 mole I₂) =

1.04x10⁻⁴ moles of S₂O₃²⁻

As dilution factor of the S₂O₃²⁻ solution was 50.0mL / 20.0mL = 2.5. Moles of the initial solution X are:

1.04x10⁻⁴ moles of S₂O₃²⁻ ₓ 2.5 = 1.60x10⁻⁴ moles of S₂O₃²⁻. In 20.0mL:

1.60x10⁻⁴ moles of S₂O₃²⁻ / 0.0200L =

0.0325M S₂O₃²⁻

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.