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# Two elements $X$(atomic weight =$75$) and $Y$(atomic weight =16) combine to give a compound having $75.8 \%\; X$. The formula of the compound is

$(a)\;XY \\(b)\;X_2Y\\(c)\;X_2Y_2\\(d)\;X_2Y_3$
Can you answer this question?

Toolbox:
• Step 1. If you have masses go onto step 2. If you have % composition of the elements. Assume the mass to be 100g, so the % becomes grams.
• Step 2. Determine the moles of each element.
• Step 3. Determine the mole ratio by dividing each elements no. of moles by the smallest value from step 2.
• Step 4. Double, triple, … to get an integer if they are not all whole numbers
$\therefore$ emprical formula $=X_2Y_3$
Hence d is the correct answer.
answered Mar 4, 2014 by
edited Mar 25, 2014