1 Clearly and carefully explain how each of the following er

1. Clearly and carefully explain how each of the following errows will affect the calculated percent iron in your unknown. (higher, lower, not affected)

A. Some of the KMnO4 soultion decomposed between the time you standardized it and the time you used it in your determination of iron.

B. Your buret leaked during the permanganate-tron titration and some of the soultion spilled on the lab bench

C. You did not stop the titration until the solution in the flask was dark purple.

D. you added 118 ml of distilled water to the flask containing the iron salt before the titration, instead of 100 mL called for.

2. MnO4^- + 5 Fe^2+ 8 H^+ -----------------> Mn^2 + 5 Fe ^3 + 4 H20

Use the balanced equation above to calculate the volume of 0.0100 M MnO4- needed to react with 0.673 g of FeCl2. SHOW WORKKKKK

Solution

A) Higher , since we require more KMnO4 to react with Iron than expected when some part of KMnO4 is decomposed, hence we overestimate iron valu.

B) Higher , some KMnO4 in buret is lost so we require more KMnO4 to react with iron, here too we overestimate iron quantity

C) Higher , a little extra KmNo4 is added evevn after titration is completed, so more KmNo4 used, more is estimated quantity of iron

D) No effect , distilled water is solvent , it doesnot effect moles of iron.

moles of FeCl2 = 0.673/126.75 = 0.0053,

moles of MnO4- required = ( 2/5) x 0.0053 =0.002124 ,

vol required = moles/M = 0.002124/0.01=0.2124 liters = 212.4 ml