Two 250 mL samples of water are drawn from a deep well bored into a large underground salt (NaCI) 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 NaCI precipitate is seen to form in Sample # 1. A. A bigger mass of NaCl precipitate will form in Sample #2.
B. A smaller mass of NaCl precipitate will form in Sample #2.
C. The same mass of NaCl precipitate will form in Sample #2.
D. No precipitate will form in Sample #2.
E. I need more information to predict whether and how much precipitate will form in Sample #2.
A student sees tiny bubbles clinging to the inside of an un-opened plastic bottle full of carbonated soft drink. The student opens the bottle, and hears a loud hiss as gas under pressure escapes from the bottle.
A. The bubbles will shrink, and some may vanish.
B. The bubbles will grow, and more may appear.
C. The bubbles won't change.
D. I need more information to predict what will happen to the bubbles.

C. The same mass of NaCl precipitate will form in Sample #2.

B. The bubbles will grow, and more may appear.

Explanation:

Solubility refers to the amount of solute that dissolves in a solvent at a particular temperature. Solubility is temperature dependent. The solubility of various substances vary with temperature as depicted in solubility curves.

If we consider the solubility curve for sodium chloride, we easily notice that the solubility of NaCl is fairly independent of temperature. The solubility variation with temperature is flat meaning that an increase in temperature has relatively little effect on the solubility of NaCl, hence, the same mass of NaCl precipitate will form in Sample #2.

For the second question, we know that in a carbonated drink, carbon dioxide is present inside the bottle under pressure. Opening the bottle means that the pressure on the liquid suddenly decreases. Less carbon dioxide is now trapped at this lower pressure, hence the extra gas in the bottle is no longer dissolved in the liquid, consequently, more bubbles form in the system .

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