SSCE VCE Chemistry Instrumental Analysis of Organic Compounds: Elemental sulfur can be used to

Question

Elemental sulfur can be used to control outbreaks of powdery mildew on grapes. However, sulfur remaining on the grapes after harvest can be converted to a number of undesirable compounds during fermentation in wine production.

A wine chemist uses atomic absorption spectroscopy to determine the amount of sulfur remaining on grapes.

In a particular analysis, 100.0 g of grapes are treated with 100.0 mL of surfactant solution to remove the sulfur remaining on the grapes when they were harvested.

25.00 mL of this surfactant solution is treated to convert all the sulfur to sulfate ions and then dried to produce an ash containing the sulfate ions.

This ash is transferred to a 10.00 mL volumetric flask containing 2.00 mL of 200 mg/L solution of barium Ba²⁺ ions.

The volume of solution in the volumetric flask is then made up to the calibration line. A precipitate of BaSO₄ forms and settles to the bottom of the volumetric flask.

A small amount of the solution containing the unreacted Ba²⁺ ions is removed from the volumetric flask and analysed using atomic absorption spectroscopy. This solution gave an absorbance of 0.11.

A calibration curve was prepared using standard solutions of 10, 20, 30 and 40 mg/L Ba²⁺ (aq).

Elemental sulfur can be used to control outbreaks of powdery mildew on grapes - VCE - SSCE Chemistry - Question 10 - 2009 - Paper 1

Worked Solution & Example Answer:Elemental sulfur can be used to control outbreaks of powdery mildew on grapes - VCE - SSCE Chemistry - Question 10 - 2009 - Paper 1

a. Determine the concentration of barium ions remaining in the 10.00 mL sample solution.

Hence determine the mass of barium ions in the 10.00 mL sample solution.

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