Concentration of solutions

Concentration of solutionsDay 4

ConcentrationA measurement of the amount of solute in a given amount of solvent or solution (unit of measurement = molarity)

Kind of like the strength of the solution

2MolarityMolarity (M)= mol solute L solution

3Volume conversion factors1 cm3 = 1 mL

1 dm3 = 1 LDiluteA dilute solution is a solution in which there is more solvent than solute.For example, to dilute some solution, you could add excess water to it.Example #1:If we put 0.500 mol of sodium hydroxide into 1.00 L of solution, what is the molarity of the solution?6Molarity= mol solute/L solnM=2.00 L0.50 mol NaOH=0.25 M NaOHExample #2:

What is the molarity if we have 80.0 g NaOH in 1.00 L of solution?

8Molarity= mol solute/L solnM=1.00 L2.00 mol NaOH=2.00 M NaOH80.0 g NaOH40.0 g NaOH1 mol NaOH=2.00 molExample #3:How many moles of KOH are in 0.50 L of 0.10 M KOH?10Molarity= mol solute cross multiply! 1 L solnmol KOH=(0.50 L)(0.10 M KOH)=0.05 mol KOHExample #4How many grams of KOH are in 2.75 L of 0.25 M KOH?Molarity = moles cross multiply! LMoles = Molarity * L = 0.25 mol/L * 2.75L = 0.69 moles KOH

0.69 mol KOH 56.097 g KOH = 38.7 g KOH 1 mole KOH (39)Molarity - DilutionSome chemicals are sold as pre-prepared concentrated solutions (stock solutions).

To be used, stock solutions usually must be diluted.

Always Add Acid

Molarity Dilution CalculationsM1V1 = M2V2

M1 Molarity of stock solutionV1 Volume of stock solution (L or mL)MD Molarity of dilute solution VD Volume of dilute solution (L or mL)Stock (original)Dilute (new solution)*In dilution calculations, the units for volume must be the same.

2.) Molarity - DilutionExample #1: How much 12.0 M HCl is required to make 2.50 L of a 0.500 M solution? Ms * Vs = MD * VD18MS VS = MD VD or M1 V1 = M2 V2

MS = 12.0 M HCl MD = 0.500 M HCl VS = ?? VD = 2.50 LVS =(0.500 M HCl)(2.50 L)(12.0 M HCl)=0.104 L HCl2.) Molarity - DilutionExample #2: What volume of a 1.50 M solution can be made using 0.0250 L of 18.0 M H2SO4?MS VS = MD VD20MS VS = MD VD

MS = 18.0 M H2SO4 MD = 1.50 M H2SO4 VS = .0250 L VD = ????VD =(18.0 M H2SO4)(.0250 L)(1.50 M H2SO4)=0.300 L H2SO4