Question

a pair of 100 ml samples of water are taken from a well bored into a large underground salt (nacl) deposit. sample #1 is from the top of the well, and is initially at 32°c. sample #2 is from a depth of 50. m, and is initially at 42°c. both samples are allowed to come to room temperature (20.°c) and 1 atm pressure. an nacl precipitate is seen to form in sample #1. two 250 ml samples of water are drawn from a deep well bored into a large underground salt (nacl) deposit. sample #1 is from the top of the well, and is initially at 42°c. sample #2 is from a depth of 150 m, and is initially at 8°c. both samples are allowed to come to room temperature (20°c) and 1 atm pressure. an nacl precipitate is seen to form in sample #1.

Explanation:

For the first experiment:

• The solubility of NaCl in water decreases with a decrease in temperature.
• Sample #1 is cooled from \(32^{\circ}C\) to \(20^{\circ}C\), and Sample #2 is cooled from \(42^{\circ}C\) to \(20^{\circ}C\).
• The larger the temperature drop, the more NaCl precipitates. Since \(42 - 20>32 - 20\), a bigger mass of NaCl precipitate will form in Sample #2.

For the second experiment:

• Sample #1 is cooled from \(42^{\circ}C\) to \(20^{\circ}C\), and Sample #2 is heated from \(8^{\circ}C\) to \(20^{\circ}C\).
• The solubility of NaCl in water increases with an increase in temperature.
• When Sample #1 is cooled, NaCl precipitates. When Sample #2 is heated, its solubility for NaCl increases relative to its initial state (\(8^{\circ}C\)), so a smaller mass of NaCl precipitate will form in Sample #2 compared to Sample #1 (assuming they have similar initial ion concentrations from the underground salt deposit).

Answer:

First experiment: A bigger mass of NaCl precipitate will form in Sample #2.
Second experiment: A smaller mass of NaCl precipitate will form in Sample #2.