Chapter 10 - An Introduction to Chemistry: Chemical Calculations ...

10.3 Molarity and Equation Stoichiometry 389
These two conversion factors provide two ways to convert from milliliters of Na 3 PO 4
solution to moles of Na 3 PO 4 .
? mL AgNO 3 soln = 25.00 mL Na 3 PO 4 soln
1 L
10 3 mL
0.500 mol Na 3 PO 4
1 L Na 3 PO 4 soln
Objective 12
? mL AgNO 3 soln = 25.00 mL Na 3 PO 4 soln
0.500 mol Na 3 PO 4
10 3 mL Na 3 PO 4 soln
The second setup requires one less conversion factor than the first setup, so we will
use it. We can now use the molar ratio to convert from moles of Na 3 PO 4 to moles of
AgNO 3 .
? mL AgNO 3 soln = 25.00 mL Na 3 PO 4 soln
0.500 mol Na 3 PO 4
10 3 mL Na 3 PO 4 soln
3 mol AgNO 3
1 mol Na 3 PO 4
We complete the problem by using the molarity of AgNO 3 to convert from moles of
AgNO 3 to volume of AgNO 3 solution. The value 1.00 M AgNO 3 provides us with
two possible conversion factors. Like any conversion factors, they can be used in the
form you see here or inverted.
1.00 mol AgNO 3
1 L AgNO 3 soln
or
1.00 mol AgNO 3
10 3 mL AgNO 3 soln
The two possible setups for the problem are below.
? mL AgNO 3 soln =
Coefficients from balanced equation
convert moles of one substance into
moles of another substance.
25.00 mL Na 3 PO 4 soln
0.500 mol Na 3 PO 4
10 3 mL Na 3 PO 4 soln
3 mol AgNO 3 10 3 mL AgNO 3 soln
1 mol Na 3 PO 4 1.00 mol AgNO 3
= 37.5 mL AgNO 3 soln
or
Molarity as a conversion
factor converts milliliters
into moles.
Molarity as a conversion
factor converts moles
into milliliters.
? mL AgNO 3 soln
Converts given
unit into liters.
Coefficients from balanced equation
convert moles of one substance into
moles of another substance.
Converts liters
into desired unit.
= 25.00 mL Na 3 PO 4 soln
1 L
10 3 mL
0.500 mol Na 3 PO 4
1 L Na 3 PO 4 soln
3 mol AgNO 3 1 L AgNO 3 soln 10 3 mL
1 mol Na 3 PO 4 1.00 mol AgNO 3 1 L
= 37.5 mL AgNO 3 soln
Molarity as a conversion
factor converts liters into moles.
Molarity as a conversion
factor converts moles into liters.