posted by katiy .
A solution contains 1.72 10-3 M Ca(NO3)2.
Determine the mass of the Ca2+ ions in 1.8 mL of this solution.
How many nitrate ions are there in 3.0 10-6 L (3.0 µL) of this solution?
(i keep doing these two wrong but not sure why)
It would have helped if you showed your work. That way I could see if there is an error in how you view the concept.
mols Ca(NO3)2 = M x L = ?
mass Ca^2+ = mols x atomic mass Ca.
moles Ca(NO3)2 = M x L = ?
mols NO3^- = twice that. Then 1 mol NO3^- = 6.02E23 ions. Convert from that.