A 240.0-mL sample of spring water was treated to convert anyiron present to Fe2+. Addition of 27.00-mL of 0.002520 MK2Cr2O7 resulted in thereaction
6Fe2+ + Cr2O72- +14H+ ----> 6Fe3+ + 2Cr3+ +7H2O
The excess K2Cr2O7 wasback-titrated with 8.80 mL of 0.00936 M Fe2+ solution.Calculate the concentration of iron in the sample in parts permillion.
Concentration of iron = _______ ppm?