Fe2+ and Sn2+; Fe3+ and Sn2+; Fe2+ and MnO4; Fe3+ and MnO4; Fe2+ and Cr2O7 2-; Fe3+ and Cr2O7 2-. Which ions will coexist in solutions? Indicate the equations.

i believe the answer is three water molecules

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.