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Mistake in Kaplan practice test

Discussion in 'Kaplan MCAT Forum' started by 909, 10.08.08.

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  1. 909


    Kaplan MCAT practice tests Sixth Edition, Practice Test 1, question #8. "The graph of boiling point versus percent solution by weight of sodium chloride in water looks like:"

    Then they show various graphs with various curvatures - straight, convex, concave, convex then concave. (Boiling point is the vertical axis, and percent weight of sodium chloride is the horizontal.)

    I'm pretty sure the listed answer is wrong, and their explanation sounds lazy: "Because when you increase the sodium chloride by a little bit, the boiling point only goes up a little, so the initial curvature of the graph cannot be steep" hence the "correct" answer is
    But after doing some calculations I'm pretty sure the correct shape is

    I think they were trying to be cute and add a little complexity to the simple formula for boiling point elevation by throwing the "percent by weight" in there, but ended up confusing themselves.

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