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Question:

Suppose the elements X and Y combine to form two compounds XY2 and X3Y2. When 0.1 mole of XY2 weighs 10 g and 0.05 mole of X3Y2 weighs 9 g, the atomic weights of X and Y are:

60, 40

20, 30

30, 20

40, 30

Solution:

nXY2=0.1=10AX+2AYAX+2AY=100... (equation 1)nX3Y2=0.05=93AX+2AY3AX+2AY=180... (equation 2)On solving equation 1 and 2 we get,AX=40,AY=30