In a very controlled experiment, a student is sure that 0.500 grams of caffeine is dissolved in 125 mL of water. The student extracts the caffeine using a single extraction of 21 mL of methylene chloride. How much caffeine is in the methylene chloride? How much remains in the water?
I assume you know K for this.
K = (x/21)/(0.5-x)/125]
x = g in methylene chloride
0.5-x = g caffeine in water layer.
To determine the amount of caffeine in the methylene chloride and the amount that remains in the water, we can use the principles of solubility and the concept of mass balance.
1. Calculate the caffeine concentration in water:
- The student initially dissolved 0.500 grams of caffeine in 125 mL of water.
- To find the concentration, divide the mass of caffeine by the volume of water:
Caffeine concentration in water = (0.500 g) / (125 mL) = 0.004 g/mL
2. Calculate the amount of caffeine in the methylene chloride:
- The student performed a single extraction using 21 mL of methylene chloride.
- Assuming complete transfer of caffeine from water to methylene chloride, we can use the principle of mass balance:
Mass of caffeine in methylene chloride = (Caffeine concentration in water) x (Volume of methylene chloride)
Mass of caffeine in methylene chloride = (0.004 g/mL) x (21 mL) = 0.084 g
3. Calculate the remaining amount of caffeine in the water:
- Since the entire amount of caffeine was extracted into the methylene chloride, the remaining amount of caffeine in the water is:
Remaining caffeine in water = Initial caffeine - Caffeine in methylene chloride
Remaining caffeine in water = 0.500 g - 0.084 g = 0.416 g
Therefore, there is approximately 0.084 grams of caffeine in the methylene chloride, and approximately 0.416 grams of caffeine remains in the water.