Hello, I am not sure how I should do this exercise, and I would appreciate some pointers... We have 6 flasks, each with a 7 ml solution in it diluted to 100 mn with distilled water (I don't think the content is relevant to the question, but if you need to know what chemicals were used, just ask me - it doesn't have any iron), and we added a standart iron solution in it (the solution:0.702 g of Iron (II) Oxalate) in 50 ml of H2O containing 1ml of concentration H2SO4), the following way: 1st flask had 0ml, the 2nd had 1 ml, the 3rd had 2 ml etc... until the 6th flask had 5 ml. We have to calculate the Fe2+ ion concentration in each of the 5 flasks. How do we do that? My idea: 0.702 g/50ml of Iron Oxalate --> We find how much that is in moles per L --> we find how much that is per millimeter --> that will be be the concentration of the 2nd flask --> x2 = concentration of the 3rd, etc... What do you think? Thank you! J.