A solved example. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html
A solution contains 0.133 g of dissolved Lead. How many moles of soduim chloride must be added to the solution to completly precipitate all of the disolved lead? What mass of sodium chloride must be added?
3 answers
a solution contains 0.133 g of dissolved lead. How many moles of sodium chloride must be added to the solution to completely precipitate all of the dissolved lead? what mass of sodium chloride must be added?
Ok so first of all equation:
Pb2+ + 2Cl- = PbCl
Then we do some stoich
so we find the mole of the lead n=m/M
n=.133/207.2
n=6.4x10^-4mol
Now by using the mole ratio
for every Lead solution ion there need to be 2 Sodium solution (sodium chloride) ions
therefore double the amount in mol
12.8x10^-4mol
or
1.28x10^-3mol
Pb2+ + 2Cl- = PbCl
Then we do some stoich
so we find the mole of the lead n=m/M
n=.133/207.2
n=6.4x10^-4mol
Now by using the mole ratio
for every Lead solution ion there need to be 2 Sodium solution (sodium chloride) ions
therefore double the amount in mol
12.8x10^-4mol
or
1.28x10^-3mol