Question

one mole sample of FeO is heated in air until it is completely converted into Fe2O3.The percent increase in weight of sample is

Answer 1

Explanation:

 Lets take weight  of FeO be 'X' 

& Fe3O4 be "y" gm

reactions occured  as follows: 

2 FeO + 1/2 O2     ----> Fe2O3 

Fe3O4 + 1/2 O2   ------> 3Fe2O3 

Molar mass of FeO =144 g 

and Fe2O3 =160 gms. 

144 g  of FeO gives to  160 g Fe2O3 

'X' g FeO will give up  160 x X/144 gm Fe2O3                                        ----(1) 

weight of Fe2O3 created by  Y gm Fe3O4  = 160 x 3Y/464                    ----(2) 

considering the total weight i.e. (X+Y) = 100.                                            -(3) 

 from equation  1,2 & 3 . 

(160 x X /144) +160 x 3y/464 = 105 

solving we get, 

X= 21.06 & Y = 78.94 

= 21.06 % & that of Fe3O4 

= 78.94 %