Honors Chemistry
Name: _______________________________________ Date: _______________ Mods: __________
Ch. 4.5 – Concentrations of Solutions

Concentrations of solutions express the relative amount of solute dissolved in a
quantity of solvent.
o The _____________________ the concentration of a solution the ________________
solute there is dissolved in solvent

Molarity (M)
o One common way to measure concentration

o
Units =
o
Molarity = _______________________________________
o
Ex:
Concentrations of Soluble Ionic Compounds (aka: electrolytes)
Concentrations can be given in terms of:
o
_________________________ dissolved in solution
► 1.5 M NaCl
► 1.0 M (NH4)2SO4
o
_______________ dissolved in solution
► Given 1.5 M NaCl, _______ M Na+
and
► Given 1.0 M (NH4)2SO4, _______ M NH4+
_______ M Cl–
and
_______ M SO42–
(each 1 mol of (NH4)2SO4 that dissolves produces 2 mols of NH4+ ions and 1 mol of
SO42– ions)
o
Practice Example #1: What is the molarity of aluminum ions and sulfate ions,
respectively, in a solution 0.8 M Al2(SO4)3?


Calculations Involving Molarity:
o
Practice Example #2: How many mols of HNO3 are present in 2.0 L of 0.20 M HNO3?
o
Practice Example #3: What volume of a 0.30 M NaOH solution contains 2 mols of
NaOH?
o
Practice Example #4: What is the molarity of a solution in which 1.4 mols of CuCl2 is
dissolved in 750 mL of water?
o
Practice Example #5: What is the molarity of a solution that contains 7.55 g Ca3N2
dissolved in 340 mL of water?
Making Solutions from a Solid Compound:
o
Must know the following in order to make a solution:
► What concentration are you making?
► What volume of the solution will you need?
o
Steps to making a solution:
1)
Using the known molarity and volume, calculate the ______________________
needed. Then convert this to ________________ using the molar mass of the
substance.
2)
Use a __________________________ to measure the calculated quantity of
the substance
o

3)
Add the masses solid into a ____________________________
___________________ that is the exact volume you wish to make.
4)
Fill the flask to the designated line with_____________________ water. Cover
the top of the flask and ________________ it several times until the solid is
completely dissolved.
Practice Example #6: How many grams of CuSO4 are needed to make 250 mL of a
0.15 M solution?
Dilutions:
o
The ____________________ the molarity, the more concentrated the solution
o
Very concentrated solutions can be ________________________ down into less
concentrated solutions by taking a small portion of the concentrated “stock” solution
and adding more water to it.
► Note: When a solution is diluted, the ____________________________ of solute
are NOT changed, but because the volume of solvent is _____________________,
there is a decrease in the molarity = diluted solution
► moles of solute in concentrated solution = moles of solute in diluted solution
o
Equation:
* Note: Any volume unit can be used, as long as it is the same on both sides
o
Practice Example #7: We have a concentrated “stock” solution of 5 M HCl but we really
need 250 mL of a 0.5 M HCl solution. How will the diluted solution be prepared?
Molarity WS
Directions: Answer the following problems. Be sure to show your work and include proper units!
1. Sea water contains roughly 28.0 g of NaCl per liter. What is the molarity of sodium chloride in sea
water?
2. What is the molarity of 245.0 g H2SO4 dissolved in 1.20 L solution?
3. What is the molarity of 5.00 g NaOH in 750.00 mL solution?
4. What volume of a 2.0 M solution of Na2CO3 would contain 0.95 moles of Na2CO3?
5. What mass (in grams) of MgCl2 would be needed to make 750 mL of a 2.25 M solution?
6. How many grams of Ca(OH)2 are needed to make 100 mL of 0.50 M solution?
7. What volume (in mL) of 12.0 M HCl is needed to contain 3.0 moles HCl.
8. Determine the molarity of these solutions:
a) 4.67 moles of K2SO4 dissolved to make 2.04 liters of solution.
b) 4.783 grams of Na2CO3 to make 10.00 liters of solution.
c) 0.897 grams of (NH4)2CO3 to make 250 mL of solution
9. Determine the molarity of Lithium ions (Li+) in each of the following:
a) 2.0 moles of LiC2H3O2 dissolved in 670 mL of water.
b) 0.85 moles of Li2S are dissolved in 0.025 liters of water.
c) 1.2 mols of Li3PO4 are dissolved in 0.5 L of water
Dilutions WS
Acids and bases can be purchased in concentrated forms (flesh eaters); however, often times we
want to use a more dilute concentration of these solutions. In this worksheet, you will need to
determine what volume of the concentrated solution (molarities listed in table below) is needed in
order to prepare the diluted solutions given in each problem.
Concentrated Solution
Acetic Acid, Glacial (CH3COOH)
Ammonium Hydroxide (NH4OH)
Formic Acid (HCOOH)
Hydrochloric Acid (HCl)
Hydrofluoric Acid (HF)
Nitric Acid (HNO3)
Perchloric Acid, 60% (HClO4)
Perchloric Acid, 70% (HClO4)
Phosphoric Acid (H3PO4)
Potassium Hydroxide (KOH)
Sodium Hydroxide (NaOH)
Sulfuric Acid (H2SO4)
Molarity of Concentrated
Stock Solution (M)
17.5
14.5
23.6
12.1
28.9
15.9
9.1
11.7
14.8
11.7
19.4
18.0
1. You needed to make 1.5 L of 0.1 M sulfuric acid. What volume of the concentrated H2SO4 will
be required for the dilution?
2. What volume of concentrated hydrochloric acid is needed to make 3.0 L of 1.0 M HCl?
3. If 15 mL of concentrated hydrofluoric acid (HF) is diluted a volume of 500 mL, what is the
molarity of the new dilute solution?
4. What volume of concentrated ammonium hydroxide is needed to make 250 mL of 0.5 M
NH4OH?
5. If 300 mL of 6.0 M HNO3 is required and only 40 mL of 15.9 M nitric acid is available, will this
be enough to make the needed 300 mL of 6.0 M HNO3 acid? Explain.
6. Only 67 mL of concentrated acetic acid is left in the laboratory and it needs to be diluted to
form a 2.0 M solution of acetic acid. What volume, in liters, of the dilute solution can be made?
7. The process of solution formation of NaOH in water is extremely exothermic. What special
precautions should I take in mixing this solution? Write down a sequence of steps I should
follow to make 1.0 L of a diluted 0.5 M solution beginning with the concentrated stock solution
of NaOH. [Be specific…type of glassware to use, etc…]