Question 1 – Gravimetric analysis calculation
Mc Smith pretzels are being analysed for their salt content – the sample was 4.59g. The pretzel was dissolved into water and then the solution was reacted with silver nitrate. The precipitate was collected, purified and dried in an oven until the mass reached a constant weight of 2.44g.
a) Write the ionic equation of this reaction. (1 mark)
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b) What are three properties required for precipitate in gravimetric analysis? Explain each briefly. (3marks)
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c) What was the % of salt in the pretzel sample? (2 marks)
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d) If the silver nitrate didn’t turn completely turn into percentage, how would the % of salt content change. Explain. (2marks)
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Question 2 – Gravimetric Analysis Questions
A 0.4872g sample of waste material from a zinc smelter was treated with nitric acid and KClO3 to convert the sulfur to sulfate. After removing the nitrated and chlorate by repeated fuming with concentration HCl, the sulfate was precipitated as barium sulfate precipitate weighed 0.1967g.
a) What is the %S in the waste material? (3 marks)
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b) What are the assumptions that you had to make in (a)?
(1 mark)
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c) What is the % of magnesium sulfate in the waste material?
(3 marks)
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d) How many sulfate ions are there in your sample of waste material?
(2 marks)
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