To calculate the total amount of caffeine that can be extracted into the three portions of methylene chloride, we need to consider the distribution coefficient and the amount of caffeine initially dissolved in water.
1. Calculate the total amount of caffeine initially dissolved in water:
- Given that 0.070 g of caffeine is dissolved in 4 mL of water.
- Convert the amount to moles by dividing by the molar mass of caffeine (194.19 g/mol):
0.070 g / 194.19 g/mol ≈ 3.60 x 10^-4 mol
2. Calculate the amount of caffeine that can be extracted into each portion of methylene chloride:
- Given that each portion of methylene chloride is 2 mL.
- The distribution coefficient for caffeine between methylene chloride and water is 4.6.
- To find the amount of caffeine extracted in each portion, multiply the initial amount of caffeine by the distribution coefficient:
3.60 x 10^-4 mol x 4.6 = 1.66 x 10^-3 mol
3. Calculate the total amount of caffeine extracted into the three portions:
- Since there are three portions of methylene chloride, multiply the amount of caffeine extracted in each portion by the number of portions:
1.66 x 10^-3 mol x 3 = 4.98 x 10^-3 mol
Therefore, the total amount of caffeine that can be extracted into the three portions of methylene chloride is approximately 4.98 x 10^-3 mol.