Let the number of \(O^{–2}\) ions be \(100\)
and the number of \(Fe^{+2}\) ions be \(X\)
The number of \(Fe^{+3}\) ions be \((93 – X)\)
\(∴ X(2) + (93 – X)3 = 200\)
\(279 – X = 200\)
\(X = 279-200\)
\(X = 79\)
∴ % of \(Fe^{+2}\) ions\(=\frac {79}{93}×100\)
≃ 85%
So, the answer is 85%.
Consider the following two reactions A and B: 
The numerical value of [molar mass of $x$ + molar mass of $y$] is ___.
Consider an A.P. $a_1,a_2,\ldots,a_n$; $a_1>0$. If $a_2-a_1=-\dfrac{3}{4}$, $a_n=\dfrac{1}{4}a_1$, and \[ \sum_{i=1}^{n} a_i=\frac{525}{2}, \] then $\sum_{i=1}^{17} a_i$ is equal to

Read More: Some Basic Concepts of Chemistry
There are two ways of classifying the matter:
Matter can exist in three physical states:
Based upon the composition, matter can be divided into two main types: