Mole concept – atomic masses from compounds

2016 Phase II 1 question

1. 1 Some Basic Concepts of Chemistry
   Suppose the elements X and Y combine to form two compounds $XY_2$ and $X_3Y_2$. When 0.1 mole of $XY_2$ weighs 10 g and 0.05 mole of $X_3Y_2$ weighs 9 g, the atomic weights of X and Y are
   A 20, 30 B 30, 20 C 40, 30 D 60, 40
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