4. A puddle of coastal seawater, caught in a depression formedby some coastal rocks at high tide, begins to evaporate as the tidegoes out. If the volume of a puddle decreases to 23% of itsoriginal volume, what is the sodium chloride concentration if itwas initially 0.449 M?
5. Iron (II) can be precipitated from a slightly basic aqueoussolution by bubbling oxygen through the solution, which converts Fe(II) to Fe (III):
                 4 Fe(OH)+ (aq) + 4 OH- (aq) +O2(aq) + 2H2O (L) ? 4 Fe(OH)3(s)
How many grams of oxygen are needed to precipitate all of theiron in 75 mL of 0.090 M Fe(II)?
