MolarityMolarity

Unit of Concentration There are many units of concentration

Molarity is most useful to the chemist

M = moles of solute

Liters of solutionLiters of solution means the total volume

of water and solute.If I want a liter of solution I will not use a

liter of water.

Unit of Concentration There are many units of concentration

Molarity is most useful to the chemist

M = moles of solute

Liters of solutionLiters of solution means the total volume

of water and solute.If I want a liter of solution I will not use a

liter of water.

Molarity ProblemsYou work them.

Molarity ProblemsYou work them.

A saline solution contains 0.90 g NaCl in exactly 100 ml of solution. What is the molarity of the solution?

Convert g to moles0.90g NaCl 1 mol NaCl

58.5 g NaCl = 0.015 mol NaCl

Take 0.015 moles/ .100 LAnswer - 0.15 mol/L or 0.15 M NaCl

A saline solution contains 0.90 g NaCl in exactly 100 ml of solution. What is the molarity of the solution?

Convert g to moles0.90g NaCl 1 mol NaCl

58.5 g NaCl = 0.015 mol NaCl

Take 0.015 moles/ .100 LAnswer - 0.15 mol/L or 0.15 M NaCl

Molarity ProblemsYou work them.

Molarity ProblemsYou work them.

How many moles of solute are present 1.5 L of 0.24 M Na2SO4?

0.24 M = x mol solve for x 1.5 L

Answer - 0.36 mol of Na2SO4

What if I asked you to find how many grams of solute are present in the previous problem.

Convert your moles to grams.

How many moles of solute are present 1.5 L of 0.24 M Na2SO4?

0.24 M = x mol solve for x 1.5 L

Answer - 0.36 mol of Na2SO4

What if I asked you to find how many grams of solute are present in the previous problem.

Convert your moles to grams.

Preparing a solutionPreparing a solutionHow would you make 500.0 ml a 0.25 M

solution of copper (II) chloride?0.25 M = mol/0.5000 L - change ml to

liters and solve for moles.You need 0.13 moles of CuCl2. Converting

to grams equals 17 grams.Final answer

Take 17 grams of CuCl2 and dissolve in enough water to make 500.0 ml of solution.

Dissolve the 17 grams in say 400 ml of water. Once the CuCl2 is dissolved add water up to 500.0 ml.

How would you make 500.0 ml a 0.25 M solution of copper (II) chloride?

0.25 M = mol/0.5000 L - change ml to liters and solve for moles.

You need 0.13 moles of CuCl2. Converting to grams equals 17 grams.

Final answer Take 17 grams of CuCl2 and dissolve in enough

water to make 500.0 ml of solution.Dissolve the 17 grams in say 400 ml of

water. Once the CuCl2 is dissolved add water up to 500.0 ml.

Preparing a solutionyour turn

Preparing a solutionyour turn

How would you prepare a solution of 0.40 M KCl? If a volume is not given assume 1 L.

0.40 M = mol/ 1 L mol = 0.40 mol needed

0.40 mol 74.6 g KCl = 3.0x101 grams KCl

1 mol KClTake 3.0x101 grams of KCl and dissolve in

enough water to make a liter of solution.

How would you prepare a solution of 0.40 M KCl? If a volume is not given assume 1 L.

0.40 M = mol/ 1 L mol = 0.40 mol needed

0.40 mol 74.6 g KCl = 3.0x101 grams KCl

1 mol KClTake 3.0x101 grams of KCl and dissolve in

enough water to make a liter of solution.