A 1.252g sample containing iron is dissolved and converted to FE 2+ followed by addition of 25ml of 0.01M k2 cr2 07. The excess K2cr207 required 6.85 ml of 0.015M. Find the percentage FE304 FW 231g/mol in the sample.

The right 7.96%
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6.85 mL of 0.015M WHAT?