Transcript Chapter 22 Sect. 2: Solubility and Concentration

CHAPTER 22 SECT. 2: SOLUBILITY AND
CONCENTRATION
DISSOLVING REVIEW

What has to take place in order for a solute to
be dissolved?
 Solvent
molecules surround the solute particles
and pull the solute particles into solution, and the
complex spreads out evenly throughout the solution
SOLUBILITY

What determines the amount of solute that is
able to dissolve in a solvent?
 Solubility:
the maximum amount of solute
that can be dissolved in a given amount of
solvent at a given temperature
 Solubility
depends on the properties of the solute and
solvent
 Some solutes are more “soluble” in some solvents than
others

This means that more of it can be dissolved in that particular
solvent than in a different solvent, or more will dissolve in a
solvent compared to another solute
CONCENTRATED VS. DILUTED

The concentration of a solution refers to the
amount of solute dissolved in a
solution
 Concentrated:
Solutions with a large amount
of solute particles
 Diluted:
particles
Solutions with a small amount of solute
CONCENTRATIONS OF SOLUTIONS

To find the concentration of a solution:

Divide the mass of the solute by the volume of
solvent

We will use units of grams of solute per 100 mL of
solvent (g/100mL)
 i.e.
the concentration of a sample of salt water is 35.9 g/100 mL
of water

You may need to set up a proportion to determine
concentration
𝟓 𝒈𝒓𝒂𝒎𝒔
𝒙
𝟐𝟓 𝒎𝑳
=
𝟏𝟎𝟎 𝒎𝑳
CALCULATING CONCENTRATIONS
1. What is the concentration of a solution in grams/100
mL when 40 grams of solute dissolve in 200 mL of
solution? 𝟒𝟎 𝒈𝒓𝒂𝒎𝒔
𝒙
𝟐𝟎𝟎 𝒎𝑳
=
𝟏𝟎𝟎 𝒎𝑳
x = 20 g
Answer: 20 g/100mL
2. A solution contains 15 grams of solute in 30 mL of
solution. What is the concentration of the solution in
g/100 mL? 𝟏𝟓 𝒈𝒓𝒂𝒎𝒔
𝒙
𝟑𝟎 𝒎𝑳
=
𝟏𝟎𝟎 𝒎𝑳
x = 50
Answer: 50 g/100mL
3. A solution has a concentration of 2 g/ 100 mL. If you
have 600 mL of the solution, how many grams of solute
do you have?
𝒙
𝟐 𝒈𝒓𝒂𝒎𝒔
𝟔𝟎𝟎 𝒎𝑳
=
𝟏𝟎𝟎 𝒎𝑳
x = 12
Answer: 12 g
TYPES OF SOLUTIONS

There are three other terms that can be used to
describe the concentration of a solution based on the
amount of solute that is dissolved

Saturated – a solution that contains all of the possible
solute that it can hold at a given temperature (no more
solute can dissolve)

Unsaturated – a solution that can dissolve more solute
at a given temperature

Supersaturated – a solution that contains more solute
than a saturated solution at the same temperature
Usually in order to produce a supersaturated solution, the solution
needs to be heated which increases the solubility of most solids
 Gases on the other hand are more soluble in liquids when the
temperature is decreased

SATURATION ANALOGY

Our classroom has 27 desks…
If there are < 27students:
unsaturated classroom – more students can
still fit in the class
 If there are 27students:
saturated classroom – can not fit anymore
students
 If there are > 27students:
supersaturated classroom– adding more
causes students to be displaced, or fall into aisles
(precipitation)

 Increase
temperature, students up and moving around the
room, more energy, more students can fit in the classroom
SOLUBILITY CURVES

A solubility curve is a graph
showing the relationship between
solubility and temperature
(or sometimes pressure)

We can use solubility curves to
figure out how much solute will
dissolve in a particular solvent at a
certain temperature

We can also use them to determine
if a solution is saturated,
unsaturated, or supersaturated
If above the curve: supersaturated
 If on the line of the curve: saturated
unsaturated
 If below the curve:

SOLUBILITY CURVES PRACTICE

1.
Use the solubility curve to the right to answer the
following questions.
What is the solubility of Ba(OH)2 in 100 mL of
water at 80˚C?
~95g/100 mL water
2.
At about what temperature will 100g of water
dissolve equal amounts of KNO3 and NaNO3?
(Hint: 100g water = 100 mL water)
3.
~73˚C
How many grams of KNO3 are needed to
produce a saturated solution at 40˚C?
~65g
4.
If 120g of NaNO3 are dissolved in 100g of water
at 20˚C, is the solution saturated, unsaturated
or super saturated? Supersaturated (above the
solubility line)
5.
If 70g of KI are dissolved in 100g of water at
30˚C, is the solution saturated, unsaturated or
super saturated?
Unsaturated (below the
solubility line)