Passage III
Students performed 3 experiments to investigate the absorption of H2O by dried chickpeas (a type of bean).
Experiment 1
A sample of 50 dried chickpeas with similar sizes and masse was selected. The total mass of the sample was measured, and the average initial mass per chickpea (CMi) was calculated. The sample was immersed in 200 mL of distilled H2O at 20°C. After 20 min, 5 chickpeas were removed from the distilled H2O and gently patted dry with a paper towel, and their total mass was then measured. The average final mass per chickpea (CMf) was calculated. At each of 6 different time thereafter, another 5 chickpeas were removed from the distilled H2O and gently patted dry with a paper towel, and their CMf was determined. The average moisture uptake per chickpea (CMU) was then calculated for each group of 5 chickpeas using the following equation:
The results are shown in Table 1.
Experiment 2
The students repeated the procedure from Experiment 1 at 4 other temperatures (see Table 2).
Experiment 3
The students repeated the procedure from Experiment 1, except that they replaced the distilled H2O with aqueous solutions of NaCl at 3 different concentrations (see Table 3).
Tables adapted from Gabriel Pinto and All Esln, "Kinetics of the Osmotic Hydration of Chickpeas." ©2004 by Division of Chemical Educatlon, lnc., American Chemical Society.
14. If a 2.0 M NaCl solution had been tested in Experiment 3, the CMU at 90 min would most likely have been:
Your Answer is
Correct Answer is H
Explanation
2.0 M is between 1.0-3.0 M, so look at table 3, the corresponding CMU at 90 minutes should be between 0.25-0.28