Answer:
6ppm
Explanation
We'll begin by calculating the concentration of the solution in mg/g. This is illustrated below:
Mass of iron = 4.5mg
Mass of water = 750g
Concentration in mg/g = 4.5/750 = 6×10¯³mg/g.
Now, we can obtain the concentration in ppm as follow:
1mg/g = 1000ppm
Therefore, 6×10¯³mg/g = 6×10¯³ x 1000 = 6ppm.