A sample is analyzed to determine its iron content Fe2+ via a redox titration with potassium...

A sample is analyzed to determine its iron content Fe2+ via a redox titration with potassium chromate as the titrant. In the titration Fe2+ is oxidized to Fe3+ and CrO4 2- is reduced to Cr 3+. What is the percent by mass of iron in the sample if 0.9087g of the sample required 45.68mL of a 0.04322 M K2CrO4 solution to reach the endpoint?

I worked out the balanced equation to be:

8H+ + 3Fe2+ + CrO4 2- = 3Fe3+ + Cr3+ + 4H2O

Expert Solution

8H+ + 3Fe2+ + CrO4 2- = 3Fe3+ + Cr3+ + 4H2O

no of moles of K2CrO4 = molarity* volume in L

= 0.04322*0.04568 = 0.00197 moles

K2CrO4 ---------> 2K⁺ + CrO4^2-

0.00197moles 0.00197moles

from balanced equation

1 mole of CrO4^2- react with 3 moles Fe²⁺

0.00197 moles CrO4^2- react with = 3*0.00197/1 = 0.00591moles of Fe⁺²

mass of Fe = no of moles* gram atomic mass

= 0.00591*56 = 0.33096g of Fe

mass percentage of Fe = 0.33096*100/0.9087 = 36.42%

queen_honey_blossom answered 11 months ago

Determination of iron by redox titration What error (+, - or 0) is introduced in the...

Determination of iron by redox titration What error (+, - or 0) is introduced in the % Fe in the unknown and briefly explain why in each case. (a) The permanganate solution becomes contaminated with organic matter before standardization. (b) The original KMnO4 solution contained some MnO2 that was not filtered out. (c) The sodium oxalate was not totally dry when it was weighed out. (d) The unknown had some of its iron already oxidized to Fe3+.

A stainless steel alloy is to be analyzed for its chromium content. A 3.00 g sample...

A stainless steel alloy is to be analyzed for its chromium content. A 3.00 g sample of the steel is used to produce 250.0 mL of a solution containing Cr2O72−. A 10.0-mL portion of this solution is added to BaCl2(aq). When the pH of the solution is properly adjusted, 0.145 g BaCrO4(s)precipitates. What is the percent Cr, by mass, in the steel sample?

0.737 g of a sample contains iron. all amount of iron is oxidied to Fe2+ on...

0.737 g of a sample contains iron. all amount of iron is oxidied to Fe2+ on Pt anode which has constant potential at 1.0 V against SCE. an iodide chemical coulometer is used to measure the amont of current (Q), the amount of released iodide needs 27.mL of thiosulfate (0.0217 N). calculate the percentage of Fe3O4 in the sample. (current 10 mA)

gravimetric determination of Iron as Fe2O3 A sample containg iron can be analyzed by precipitation of...

gravimetric determination of Iron as Fe2O3 A sample containg iron can be analyzed by precipitation of the hydrous oxide from basic solution, followed by ignition to Fe2O3: Fe3+ + (2+x)H2O ----> FeOOH* xH2O(s) + 3H+ FeOOH * xH2O ------> Fe2O3 (s) weigh three samples of unknown containg enough Fe to produce ~0.3g of Fe2O3 In my experiment, unknow sample weight: 0.75g 0.80 0.70 Fe2O3 collected from unknow: 0.05g 0.04 g 0.03g how do I calculate (1)% Fe in unknown sample...

A 25.0-mL sample of lambic (a sour Belgian beer) was analyzed for its acetic acid content...

A 25.0-mL sample of lambic (a sour Belgian beer) was analyzed for its acetic acid content by an electrochemical method. The pure sample registered a signal of 2.55 mA. A standard solution of 0.500 mL of 0.109 M acetic acid was added, and the signal increased to 2.98 mA. What is the acetic acid concentration in the original lambic sample?

A 7.279 gram sample of meat was analyzed for its nitrogen content using kjeldahl method. Upon...

A 7.279 gram sample of meat was analyzed for its nitrogen content using kjeldahl method. Upon digestion, the ammonia liberated was collected in 250 ml of 0.855 M H3BO3. The resulting solution was titrated with 37.25 ml of 0.3122 M HCl using mixed indicator. Determine the % protein in the sample using 6.25 as a factor for meat product ? Answer: 13.98%

A mixture of MgBr2 and inert material is analyzed to determine the Mg content. First the...

A mixture of MgBr2 and inert material is analyzed to determine the Mg content. First the mixture is dissolved in water. Then all of the bromide ion is precipitated as AgBr by the addition of an excess of silver nitrate. MgBr2(aq) + 2AgNO3(aq) 2AgBr(s) + Mg(NO3)2(aq) In one experiment, a 0.8107 g sample of the mixture resulted in 1.1739 g of AgBr. Determine the percent (by mass) of Mg in the mixture.

A 1.6g amount of a paint sample was analyzed for lead content by a highly precise...

A 1.6g amount of a paint sample was analyzed for lead content by a highly precise method and 5.2% sampling RSD was obtained. This should be the sample weight to improve RSD to 3.1% A) 0.57g B) 2.7g C)4.5g D) None of the above

A 0.3999g sample of reagent grade Al2(SO4)3.xH2O was dissolved and analyzed for its aluminum content gravimetrically...

A 0.3999g sample of reagent grade Al2(SO4)3.xH2O was dissolved and analyzed for its aluminum content gravimetrically by precipitation as the aluminum oxinate complex, AL(C9H6NO)3, the precipitate weighing 0.4185g. Calculate the number of molecules of water of crystallization.

A 250.0 mL sample of spring water was treated to convert any iron present to Fe2+....

A 250.0 mL sample of spring water was treated to convert any iron present to Fe2+. Addition of 24.00 mL of 0.002543 M K2Cr2O7 resulted in the reaction 6Fe2+ + Cr2O72- + 14H+ ---> 6Fe3+ + 2Cr3+ + 7H2O The excess K2Cr2O7 was back titrated with 8.02 mL of 0.00971 M Fe2+ solution. Calculate the concentration of iron in the sample in ppm.

Question