The unit for molarity (M) is "moles of solute"/"liters of solution"="mol/L"moles of soluteliters of solution=mol/L.
When diluting a solution, the amount of solute remains constant, but the volume of the solution increases.
The formula for the dilution of a solution is given below:
"M"_1"V"_1"=M"_2"V"_2"M1V1=M2V2,
where "M"M is molarity and "V"V is volume of the solution in liters (L).
Known
"M"_1="9.0 M"="9.0 mol/L"M1=9.0 M=9.0 mol/L
"M"_2="3.5 M"="3.5 mol/L"M2=3.5 M=3.5 mol/L
"V"_2="0.35 L"V2=0.35 L
Unknown
"V"_1"V1
Solution
Rearrange the dilution formula to isolate "V"_1"V1. Substitute the known values into the equation and solve.
"V"_1=("M"_2"V"_2)/("M"_1)V1=M2V2M1
"V"_1=(3.5cancel"M"xx"0.35 L")/(9.0cancel"M")="0.14 L" rounded to two significant figures
"V"_1=0.14 cancel"L"xx(1000 "mL")/(1 cancel"L")="140 mL" rounded to two significant figures
