Question

We know that balancing of a chemical equation is entirely bases on law of conservation of mass. However the concept of Principle of Atom Conservation (POAC) can also be related to law of consevation of mass in a chemical reaction. So, POAC can also act as a technique for balancing a chemical equation. For example, for a reaction:
`ABC_(3) rarr AB+C_(2)`
On applying POAC for A , B and C and related the equations , we get : `(n_(ABC_(3)))/(2) =(n_(AB))/(2) =(n_(C_(2)))/(3)`
(`n_(x)` : number of moles of X)
Thus , the cofficients of `ABC_(3)` , AB and `C_(2)` in the balanced chemical equation will be 2,2 and 3 respectively and the balanced chemical equation can be represented as ,
`2ABC_(3) rarr 2AB + 3C_(2)`
If in the above question, the atomic masses of X and Y are 10 and 30 respectively, then the mass of `XY_(3)` formed when 120 g of `Y_(2)` reacts completely with X is:
A. 133.3 g
B. 200 g
C. 266.5 g
D. 400 g.

Answer 1

Correct Answer - A
on applying POAC for X and Y respectively, we get
`1xxn_X=1xxn_(XY_3)`…(1)
`2xxn_(Y_2)=3xxn_(XY_3)`…(2)
by (3) & (4) , `n_(Y_2)=1.5xxn_X`
from (3) and (4) `n_X/2=n_(Y_2)/3=n_(XY_3)/2`
`:.` Balanced equatin : `2X+3Y_2to3XY_3`
`n_(Y_2)=120/60 :. n_(XY_3)=4/3=2`
`:. m_(XY_3)=4/3xx100=133.3 g`