AP EAMCET Engineering 26 Apr 2017 Shift 1 Paper

The formula of first oxide is XO2 which means one mole of X contains 2 mole of oxygen.
For second oxide, there is 40% of ( X) which means there is 60% of oxygen.
Now, for 40% of X, we have 2×60%=80% of oxygen,
The moles of oxygen for 100% of X can be calculated as:
Moles‌of‌oxygen=

2×60

4

=3‌moles
Therefore, the formula of second oxide will be XO3.