Which of these salts contains the greatest % of X by mass? XF XF2 or X2F3

Question

explain which one and why

Answer 1

You are comparing the mass fraction of X (percentage is just 100x the fraction). Let's call the molar mass of X, M.

1) M/(M+19), 2) M/(M+38, and 3) 2M/(2M+57)

Obviously the fraction of X in (1) is more than in (2). In order to compare 3 with the others, divide top and bottom by 2: M/(M+ (3/2)19). (1) is still the compound with the highest composition of X

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