The compound of some element has the formula E2O3, and the mass fraction of the element in it is 68.42%. Install the item.

To start solving, we write down the oxide formula of this element and find the percentage of oxygen in it:
W (O) = 100% – 68.42% = 31.58%
The ratio of the number of their atoms in the oxide is 2/3 or 1 / 1.5.
To find the molar mass of an element, you need to write down the proportion:
0.6842 – 0.3158
M – 16
Location: 0.6842 / M = 0.0197
The element content will be one and a half times less than the oxygen content:
0.6842 / M = 0.0197 / 1.5
0.6842 / M = 0.0137
Whence M is equal to: 0.6842 / 0.0131 = 52.2 g / mol
According to the periodic table, this element is chrome!
Cr2O3 oxide formula