Some Basic Concepts Of Chemistry Question 67
Question: 2.0 g of a sample contains mixture of $ SiO _2 $ and $ Fe _2{O_3} $ . On very strong heating, it leaves a residue weighing 1.96 g. The reaction responsible for loss of mass is given below.
$ Fe _2O _3(s)\to Fe _3O _4(s)+O(g), $ (unbalance equation) What is the percentage by mass of $ SiO _2 $ in original sample?
Options:
A) 100%
B) 20%
C) 40%
D) 60%
Show Answer
Answer:
Correct Answer: C
Solution:
[c] $ 3Fe _2O _3(s)\ to 2Fe _3O _4+\frac{1}{2}O _2 $ 480 g $ Fe _2O _3 $ provide $ 16g,O _2 $ . For loss of $ 0.04gO _2\ to 0.04\times \frac{480}{16}=1.2g,Fe _2O _3 $ % by mass of $ SiO _2=\frac{0.8}{2.0}\times 100=40% $ %
