Abnormal molar mass and van 't Hoff factor

Why this is asked: i > 1 means the molar mass calculated from the observed colligative property comes out lower than the true value — dissociation, more particles than expected. i < 1 means it comes out higher — association, like acetic acid dimerising in benzene, fewer particles than expected — and getting which direction the "abnormal" molar mass shifts is exactly what these questions test.

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