9.4 - Estimation of Dissolved Oxygen by Redox Titration (Leaving Cert Chemistry): Quizzes
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12 questions from this quiz
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Practise the questions
12 questions from this quiz
What is the name of the method used to estimate dissolved oxygen in water samples?
What is the name of the method used to estimate dissolved oxygen in water samples?
Winkler's method
Which chemical reacts with dissolved oxygen to form manganese (IV) hydroxide?
Which chemical reacts with dissolved oxygen to form manganese (IV) hydroxide?
Manganese (II) sulfate
What is the molarity of the sodium thiosulfate solution used in this experiment?
What is the molarity of the sodium thiosulfate solution used in this experiment?
0.005 M
Why must the reagent bottle be filled completely with the water sample?
Why must the reagent bottle be filled completely with the water sample?
To ensure no air is trapped
What colour is the first precipitate that forms in this experiment?
What colour is the first precipitate that forms in this experiment?
White
Why is concentrated sulfuric acid added to the water sample?
Why is concentrated sulfuric acid added to the water sample?
To release iodine from potassium iodide
What colour is the solution after the brown precipitate dissolves?
What colour is the solution after the brown precipitate dissolves?
Golden-brown
What volume of iodine solution is pipetted into the conical flask for titration?
What volume of iodine solution is pipetted into the conical flask for titration?
50 cm³
When should starch indicator be added during the titration?
When should starch indicator be added during the titration?
When solution turns pale yellow
What indicates the endpoint of the titration?
What indicates the endpoint of the titration?
Blue colour disappears
How are moles of dissolved oxygen () calculated from moles of thiosulfate?
How are moles of dissolved oxygen () calculated from moles of thiosulfate?
Divide by 4
In what units is the dissolved oxygen concentration expressed?
In what units is the dissolved oxygen concentration expressed?
Parts per million (ppm)