posted by Mary .
How many grams of potassium phosphate must be dissolved in 3.75 Liters of water to produce a soltuion that contains 8*10^23 potassium ions?
You want 8E23 K ions. That is 8E23/6.02E23 moles K ions = 1.33 moles K ions. Convert to moles K3PO4. That will be 1.33 mols K ions x (1 mol K3PO4/3 moles K ions) = 0.443 moles K3PO4.
moles K3PO4 = grams/molar mass. Solve for grams. Note: do you really care what the volume. This many K ions will this many K ions in a tub or a lake.