Question
An oxide of iron contains 69.9\% iron, its empirical formula, is: (Given: Molar mass of Fe and O are 56 and 16 g mol^ -1 respectively.)
JEE Main
Chemistry
Some Basic Concepts of Chemistry
2026
JEE Main 2026 (06 April Shift 1)
JEE Main Chemistry Question (2026) — Solution
Options
- A. FeO
- B. Fe _2 O _3
- C. Fe _3 O _4
- D. FeO _3
Answer
B. Fe _2 O _3
Step-by-step solution
Mass percentage of Fe = 69.9\% Mass percentage of O = 100\% - 69.9\% = 30.1\% Number of moles of Fe = 69.9 56 = 1.248 Number of moles of O = 30.1 16 = 1.881 Molar ratio of Fe : O = 1.248 : 1.881 Dividing by the smallest value, the ratio is 1.248 1.248 : 1.881 1.248 = 1 : 1.5 Multiplying by 2 to get the simplest whole number ratio, we get 2 : 3. The empirical formula is Fe _2 O _3. Answer: Fe _2 O _3
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