[Danial]

1.5L of a solution that is 12 ppm in K+ starting from solid K4Fe(CN)6

first converted ppm into grams
m/1500g x10^6 = 12
therefore m = 18000/10^6 = 0.018g
finding moles of K

0.018/39.0983 = 4.6x10^-4
converting to moles of original compound
4.6x10^-4 / 4
= 1.151 x10^-4
converting to mass of original compound
1.151 x10^-4 x 368.3582 (molar mass of it)
= 0.04g
the reason im checking is because 0.04g isnt very big
the previous answer to a similar was like 1.9g

thanks

[Borek]

Looks OK to me. Perhaps more like 0.042g.