1. A 0.9132-gram sample of iron ore is dissolved in aqueous hydrochloric acid. I

Question

1. A 0.9132-gram sample of iron ore is dissolved in aqueous hydrochloric acid. It dissolves completely and in the process, all of the iron goes into solution as Fe2+ ion. The following chemical reaction is a redox reaction and it is the focus of the question:

The acid solution containing all of the Fe2+ is placed in a beaker. A solution of aqueous potassium dichromate is used to fill a burette. A redox titration is performed. A volume of exactly 28.72 mL of 0.05051M K2Cr2O7 (aq) is required to complete the redox titration. The unbalanced redox equation is:

Fe2+(aq) + K2Cr2O7(aq) (in acid) --> Fe3+(aq) + Cr3+(aq)

What is the mass percent iron in the original sample of iron ore? Please show all your work.

HINT: if you need to add potassium to balance

Explanation / Answer

6 Fe2+ + K2Cr2O7 + 14 H+ => 6 Fe3+ + 2 Cr3+ + 7 H2O + 2 K+

Moles of K2Cr2O7 = volume x concentration of K2Cr2O7

= 28.72/1000 x 0.05051 = 0.00145065 mol


Moles of Fe2+ = 6 x moles of K2Cr2O7

= 6 x 0.00145065 = 0.00870388 mol


Mass of Fe = moles x molar mass of Fe

= 0.00870388 x 55.845 = 0.48607 g


Mass% of Fe = mass of Fe/mass of sample x 100%

= 0.48607/0.9132 x 100%

= 53.23%

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.