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iodine is required for a healthy diet - Scottish Highers Chemistry - Question 11 - 2018
Question 11
iodine is required for a healthy diet. Food grown in certain parts of the world is low in iodine. To prevent iodine deficiency in people’s diets, table salt can be ‘... show full transcript
Worked Solution & Example Answer:iodine is required for a healthy diet - Scottish Highers Chemistry - Question 11 - 2018
Step 1
Describe a procedure to accurately weigh out a 50.0 g sample of iodised table salt.
Answer
To accurately weigh a 50.0 g sample of iodised table salt, use a balance. First, ensure the balance is calibrated and set to zero (tare) with the weighing boat or paper. Gradually add iodised salt until the balance reads exactly 50.0 g. Take care to avoid adding excess salt, and confirm the weight before removing the sample from the balance.
Step 2
Step 3
Calculate the average volume, in cm³, of sodium thiosulfate solution that should be used to determine the number of moles of iodine released.
Answer
To calculate the average volume of sodium thiosulfate solution used:
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Add the volumes of all samples:
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Divide by the number of samples (3):
ext{Average Volume} = rac{29.0 ext{ cm}^3}{3} = 9.67 ext{ cm}^3
Step 4
Calculate the number of moles of iodine released from 50 cm³ of the standard salt solution.
Answer
To calculate the number of moles of iodine released:
- Use the average volume of sodium thiosulfate from part (c)(i) which is 9.67 cm³:
- Calculate moles of sodium thiosulfate:
Using the concentration of sodium thiosulfate (0.0010 mol/dm³):
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According to the reaction, the mole ratio of I₂ to Na₂S₂O₃ is 1:2, thus:
ext{Moles of I₂} = rac{9.67 imes 10^{-6}}{2} = 4.84 imes 10^{-6} ext{ moles}