This particular experiment explores the infrared spectroscopy technique used to

Question

This particular experiment explores the infrared spectroscopy technique used to isolate benzoic acid and caffeine in soda and lemonade. The following methodology was followed:

For the cola sample, the mass of caffeine was found to be 0.112 g and the mass of benzoic acid was found to be 0.07 g. On the other hand, for the lemonade sample, the mass of caffeine was found to be 0.11 g and the mass of benzoic acid was found to be 0.06 g.

1. Calculate the concentrations of benzoic acid and caffeine in both samples (cola and lemonade) in grams per liter (g/L). Show full working along with the final concentration's uncertainty for each.

2. Can you tell from this experimental method whether the Food Additive 210 was originally present as sodium, potassium benzoate or benzoic acid? Give a detailed explanation.

Collect samples (150 mL) of soft drinks (you need one sample of lemonade and one of cola) in 500 mL conical flasks. Record the brand name (if provided). A. Isolation of caffeine: (i) Add 2 g of Na2COs to each sample and dissolve. This makes the solution basic test a drop of the solution with pH paper (not litmus paper) it should be about 8 or 9; add more NazCOs if necessary.

Explanation / Answer

1)

Concentration in grams per liter (g/L) = mass of solute / /liter of solution

Concentrations of benzoic acid and caffeine in cola sample:

Volume of cola sample is 150 mL ( 0.150 in liters)

Mass of benzoic acid = 0.07 g

Concentration of benzoic acid = 0.07 g / 0.150 L = 0.467 g/L

Mass of caffeine = 0.112 g

Concentration of caffeine = 0.112 g / 0.150 L = 0.7467 g/L

Concentrations of benzoic acid and caffeine in lemonade sample:

Volume of lemonade sample is 150 mL ( 0.150 in liters)

Mass of benzoic acid = 0.06 g

Concentration of benzoic acid = 0.06 g / 0.150 L = 0.400 g/L

Mass of caffeine = 0.11 g

Concentration of caffeine = 0.11 g / 0.150 L = 0.733 g/L

Concentrations are not exact in both cola and lemonade sample.

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