# Chemistry 11 test question... urgent?

Question 5 (6 points)
In an investigation to find the amount of caffeine in a prepared coffee solution, caffeine reacts with an excess accurately known amount of iodine in an acidic environment, forming an insoluble precipitate (Equation 1). Then the insoluble precipitate is removed by filtration.
Equation 1:
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Question 5 (6 points)

In an investigation to find the amount of caffeine in a prepared coffee solution, caffeine reacts with an excess accurately known amount of iodine in an acidic environment, forming an insoluble precipitate (Equation 1). Then the insoluble precipitate is removed by filtration.

Equation 1:

CAFFEINE (aq) + 2I2 (aq) + KI (aq)+ H2SO4 (aq) → CAFFEINE .HI .I4 (s) + KHSO4 (aq)

Looking at Equation 1, a Grade 11 student was given a sample of coffee that was assumed to contain 0.150 grams of caffeine (molar mass = 194.19 g.mol-1) and was instructed to add it to 0.635 grams of iodine, I2 solution. Assuming there was no change in volume upon mixing, a reaction took place between the reactants shown in BOLD only (as KI and H2SO4 are catalysts). She filtered the solution and weighed the formed precipitate. She recorded all relevant qualitative and quantitative observations throughout the experiment.

Using Equation 1, the student was asked to identify the limiting reactant and calculate the theoretical yield (mass of formed precipitate) for the reaction. Show ALL calculations that the student would have done.

In an investigation to find the amount of caffeine in a prepared coffee solution, caffeine reacts with an excess accurately known amount of iodine in an acidic environment, forming an insoluble precipitate (Equation 1). Then the insoluble precipitate is removed by filtration.

Equation 1:

CAFFEINE (aq) + 2I2 (aq) + KI (aq)+ H2SO4 (aq) → CAFFEINE .HI .I4 (s) + KHSO4 (aq)

Looking at Equation 1, a Grade 11 student was given a sample of coffee that was assumed to contain 0.150 grams of caffeine (molar mass = 194.19 g.mol-1) and was instructed to add it to 0.635 grams of iodine, I2 solution. Assuming there was no change in volume upon mixing, a reaction took place between the reactants shown in BOLD only (as KI and H2SO4 are catalysts). She filtered the solution and weighed the formed precipitate. She recorded all relevant qualitative and quantitative observations throughout the experiment.

Using Equation 1, the student was asked to identify the limiting reactant and calculate the theoretical yield (mass of formed precipitate) for the reaction. Show ALL calculations that the student would have done.

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