IONIC COMPOUNDS
Compounds in Aqueous Solution
Many reactions involve ionic compounds.
When a substance is dissolved in water, it is called an aqueous sol’n (aq)
KMnO4 in water
K+(aq) + MnO4-(aq)
Aqueous Solutions
How do we know ions are present in aqueous solutions?
The solutions conduct electricity.
They are called ELECTROLYTES
HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.
Aqueous Solutions
Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes.
Examples include:
sugar
ethanol
ethylene glycol
Three types of electrolytes
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
strong
weak
nonelectrolyte
Electrolytes in the Body
Carry messages to
and from the brain
as electrical signals
Maintain cellular
function with the
correct
concentrations
electrolytes
Make your own
Electrolyte
50-70 g sugar
One liter of warm water
Pinch of salt
200ml of sugar free fruit
squash
Mix, cool, and drink
Concentration of Solute
The amount of solute in a solution
is given by its concentration.
Molarity (M) =
moles solute
liters of solution
Making a Molar Solution
So, you want to make a molar sol’n?
INFORMATION YOU NEED TO MAKE SOL’N
- Volume needed (in mL or L)
- Concentration needed (M)
- Periodic Table & Calculator
Ex. Make 1L of 1M NaCl
How to Make 1L of 1M NaCl
-Volume needed = 1.0L
-[Concentration] = 1mol
So, how much does 1mol weigh???
1 mol of NaCl = 22.99 + 35.453 = 58.44g
So, what do I do with that
number????
1 mol of NaCl = 22.99 + 35.453 = 58.44g
So, I weigh out 58.44g of
= “Quantity
NaCl & put into a g.cyl QSSufficient”
Means add as
and add water until it much water as
you need to get
reaches 1L (“QS”) the final volume
you want 
I now have 1L of a 1M NaCl
sol’n
1.0 L of water
was used to
make 1.0 L of
solution. Notice
the water left
over.
What if I want 0.5L
of 1M NaCl?
xM =
1 M = y mol
0.5L
y mol
zL
y = 0.5 mol
0.5 mol (58.44 g/mol) = 29.22g NaCl
xM =
y mol
zL
So, I weigh out 29.22g of
NaCl & put into a g.cyl
and add water until it
reaches 0.5L (“QS”)
I now have 0.5L of a 1M
NaCl sol’n
Make 400mL of 1.2M NaCl
-Volume needed = 400mL
-Concentration = 1.2M
xM =
y mol
zL
1.2 M = y mol
0.4 L
-
Solve for y moles
y mol = (1.2 M)(0.4L)
= 0.48 mol NaCl
-
Change mol to g
0.48 mol NaCl (58.44g/mol)
= 28.1 g NaCl, QS to 0.4L
Dissolve 5.00 g of NiCl2•6 H2O in enough water to make 250 mL of solution. Calculate the Molarity.
Step 1: Calculate moles of NiCl2•6H2O
5.00 g •
1 mol
= 0.0210 mol
237.7 g
Step 2: Calculate Molarity
0.0210 mol
= 0.0841 M
0.250 L
[NiCl2•6 H2O ] = 0.0841 M
“The concentration of … is 0.0841 MOLAR”
More Practice ...
What mass of oxalic acid, H2C2O4, is required to
make 250 mL of a 0.05 M solution?
xM =
y mol
zL
ymol=xM•zL
Step 1: Change mL to L
250 mL * 1L/1000mL = 0.250 L
Step 2: Calculate
Molarity = (0.0500 mol/L) (0.250 L) = 0.0125M
Step 3: Convert moles to grams
(0.0125 mol)(90.00 g/mol) =
1.13 g