JEE MainChemistrySolutions
A 6.92 g sample of a non-stoichiometric iron oxide, Fe _ 0.95 O , is dissolved and titrated against a 0.5 M standard solution of KMnO ₄ in an acidic medium. The volume of KMnO ₄ solution required for complete oxidation is ______ mL. (Given: Atomic masses of Fe = 56 , O = 16 )
Correct answer
34
Step-by-step solution
First, calculate the molar mass of Fe _ 0.95 O : Molar mass = (0.95 56) + 16 = 53.2 + 16 = 69.2 g/mol . Moles of Fe _ 0.95 O in the sample = 6.92 69.2 = 0.1 mol . Next, find the n-factor of Fe _ 0.95 O . Let the moles of Fe ²⁺ be a and Fe ³⁺ be b in 1 mole of the compound. a + b = 0.95 2a + 3b = 2 Multiplying the first equation by 2: 2a + 2b = 1.90 Subtracting this from the second equation: b = 0.10 Thus, a = 0.95 - 0.10 = 0.85 . The n-factor of Fe _ 0.95 O is the number of moles of Fe ²⁺ oxidized to Fe ³⁺ per mole