4 moles as their raport is 4/2 or 2/1
Grinding as it’s a physical not chemical change :)
Answer: The correct option is 3.
Explanation: We are given a compound which is made up of iron and oxygen only. The ratio of the two are given as:

This means that, number of iron ions are 2
Number of oxide ions are 3
From the above information, the formula becomes : 
The valency of iron = 3
Valency of oxide = 2
This compound is named as iron (III) oxide.
Hence, the correct option is 3
Answer:
i think its the first one not 100% on it tho but i know for a fact its NOT c
Explanation: