Question

Elements X, Y and Z have valencies 1, 3 and 4 respectively. Formula unit masses of their oxides are 62, 102 and 64 respectively. If atomic mass of Z is divided by the difference in atomic masses of X and Y then value obtained is the atomic number of which of the following elements?

• A. Carbon
• B. Nitrogen
• C. Oxygen
• D. Fluorine

Answer 1

Answer: (C)

Oxygen

Element X is Na.Its oxide is $N{a}_{2}O$ and mass will be = 23 + 23 + 16 = 62
Element Y is Al and oxide is $A{l}_2{O}_3$ and mass will be 27+ 27 + {16*3} = 102.
Element Z is sulphur and oxide is $S{O}_2$ and mass = 32 + {2*16} = 64
Difference in atomic mass of X and Y = 4.
32/4 = 8 = Oxygen's atomic no.