white region, making (G) the best answer.
Passage III
1 . B According to Table 1, potassium hydroxide produced 2 ions, had a molar mass of 56.11
g/mol, and had a ΔH°diss of −57.6 kJ/mol. Magnesium sulfate produced 2 ions, had a molar
mass of 120.38 g/mol, and had a ΔH°diss of −91.0 kJ/mol. Use POE. Student 1 writes, The
solution containing Salt B had a higher boiling point because Salt B produces more ions
in solution than Salt A. These findings do not agree with Table 1 for the given substances,
which produced the same number of ions. Eliminate (C). Student 2 writes, The solution
containing Salt B had a higher boiling point because it had a lower molar mass (the mass
of 6.02 × 10^23 particles). Salt B in this question is magnesium sulfate, which does not have a
lower molar mass than potassium hydroxide, so you can eliminate (A) and (D). This leaves
only (B), and the findings in the table do agree with Student 3’s hypothesis.
2 . G The passage gives the following information: The boiling temperature for the solution of
Salt A was measured to be 104°C. The procedure was repeated with Salt B, which resulted
in a boiling temperature of 110°C. According to this question, ammonium nitrate has a
boiling point of 107°C, right between Salts A and B. According to Student 2, the solution
containing Salt B had a higher boiling point because it had a lower molar mass. Therefore,
because ammonium nitrate has a higher boiling point than Salt A, it must have a lower molar
mass. Only (G) can work. Choices (H) and (J) can be eliminated because Student 2 does not
discuss enthalpy change.
3 . A According to Student 2, the salt with the lower molar mass will result in more particles. In
other words, the lower the molar mass of a substance, the more particles it will produce.
According to Table 1, sodium chloride has a molar mass of 58.4 g/mol, potassium hydroxide
has a molar mass of 56.11 g/mol, and magnesium sulfate has a molar mass of 120.38 g/mol.
Since potassium hydroxide has the lowest molar mass, it should produce the most particles.
With this information alone, you can eliminate (B), (C), and (D). Only (A) remains and puts
the substances in the correct relation to one another.
4 . F The passage states, the mixture was heated and temperature readings acquired every 30 sec
until the solution reached a full boil and the solid had completely dissolved. Since the
mixture is only heated, it can be inferred that its temperature increases only. There’s no
indication that the substance is ever cooled, so (F) is the only answer supported by
information from the passage.
5 . D Student 3 offers the following hypothesis: The solution containing the salt with the more
