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(1)

Concentration and Reading

Solubility Curves

(2)

Concentrations of Solutions

• A measure of the amount of solute dissolved

in a solvent is concentration.

Concentrated or Dilute? Solutions can be

described as being concentrated or dilute. But these two terms do not tell you the amount of solute that is dissolved.

The next slide shows how to calculate

concentration.

(3)

Calculating concentration

What is the concentration of a solution that has 15g of salt dissolved in 175mL of water?

Step 1 one equation for finding concentration is the following:

concentration= grams of solute/ milliters of solvent

Step 2 Replace grams of solute and milliters of solvent with the value given, and solve

15g salt/ 175mL water = .2g/mL

(4)

1. what is the concentration of solution A if it has 55g of sugar dissolved in 500ml of

water?

2. What is the concentration of solution B if it has 36g of sugar dissolved in 144ml of

water?

(5)

1. concentration= grams of solute/ milliters of solvent

= 55g/500ml =.11g/ml of salt

2. concentration= grams of solute/ milliters of solvent

= 36g/144ml

=.25g/ml of salt

(6)

SOLUBILITY

FORMULAS

amount of solute amount of solvent

amount of solute amount of solvent

=

(7)

1.The solubility of a solid is

15g / 100g of water. How

many grams of the solid

must be dissolved in 1 kg of

water to make a saturated

solution?

(8)

SOLUBILITY PROBLEMS

amount of solute amount of solvent

amount of solute amount of solvent

=

15 g

---100g

=

X

---1000g

X=150g

15g X 1000g 100g

(9)

SOLUBILITY

EXAMPLES

2. If you have 50g in 500g of water, using solubility from problem #1, is the solution saturated?

15g

---100g

=

X

---500g

X=75g is saturated

No, 50 g is not saturated! 15 g x 500g

(10)

SOLUBILITY

EXAMPLES

3. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. How much of the solute must be dissolved in 250g of water at 20 C to prepare a saturated solution?

5g

---100g

=

X

---250g

X=12.5g to prepare a

saturated solution

5g x 250g

(11)

SOLUBILITY

EXAMPLES

4. The solubility of a solute is 5g/100g water at 20 C and 7.5g/100g water at 50 C. If a saturated

solution is prepared using 200g water at 50 C, then allowed to cool to 20 C:

a. Will it still be saturated?

(12)

SOLUBILITY

EXAMPLES

Will it still be saturated? @ 50 C:

7.5g

---100g

=

X

---200g

X=15g to prepare a

saturated solution @

50 C

7.5g x 200g 100g

(13)

SOLUBILITY

EXAMPLES

Will it still be saturated? Now cool it to 20 C:

5g

---100g

=

X

---200g

X=10g to prepare a

saturated solution @

20 C

5g x 200g 100g

(14)

SOLUBILITY

EXAMPLES

Will it still be saturated? Now cool it to 20 C:

15g > 10g

@ 20 C so its

supersaturated!!

(15)

SOLUBILITY

EXAMPLES

How much will precipitate out?

5g

---100g

=

X

---200g

X=10g to prepare a

saturated solution @

20 C

7.5g

---100g

X

---200g

=

X=15g to prepare a

saturated solution @

50 C

(16)

SOLUBILITY

EXAMPLES

How much will precipitate out?

(17)

Formulas

amount of solute amount of solvent

concentration= grams of solute/

milliters of solvent

(18)

 1. What is the concentratio of a solution

containing 7.8 g of MgCl2 in 725 mL of water?

 Given 7.8g MgCl2 ; 725mL water

 Work concentration= amount of solute  milliters of solvent

=7.8gMgCl2/725mLwater

(19)

 2. What is the concentration 160.0 g of

NaCl in 458mL water?

 Given 160.0g NaCl ; 485mL water

 Work concentration = amount of solute

 milliters of solvent  = 160.0gNaCl/485mL water

(20)

 3. What is the concentration 35.0 g of

MgCl2 in 250mL water?

 Given g MgCl2 ; 250mL water

 Work concentration = amount of solute

 milliters of solvent  = 35gMgCl2/250mL water

(21)

 The solubility of a solid is 15g / 100g of

water. How many grams of the solid must be dissolved in 1 kg of water to make a

saturated solution?

 Given: 15g/100g of water ; 1000g of water  work:

(22)

SOLUBILITY PROBLEMS

amount of solute amount of solvent

amount of solute amount of solvent

=

15 g

---100g

=

X

---1000g

X=150g

15g X 1000g 100g

(23)

What is Solubility?

Solubility: the maximum amount of

solute that will dissolve in a certain amount of solvent at a given temperature

Solute = substance dissolvedSolvent = does the dissolving

 Example: __ grams of salt (NaCl) in 100 g

(24)

Temperature and Solubility

Temperature affects how much of the solute

can be dissolved by the solvent.

Note: Increasing the temperature does not always

increase the solubility…think about what happens to dissolved gas in your soda when its heated

Solubility curves: used to show how the

solubility of a substance changes with temperature.

(25)

Solubility Curves

Solubility indicates the amount of solute that will dissolve in a given amount of solvent at a specific temperature.

For this curve,

 X-Axis

 Temperature

 Y-Axis

 How Much Solute Dissolves in 100g of

Water

 Various Lines

(26)

Solubility Curves

CO2

Saturated

Supersaturated

(27)

Using an available solubility curve, classify as

unsaturated, saturated, or supersaturated.

80 g NaNO3 @ 30oC

45 g KCl @ 60oC

30 g KClO3 @ 30oC

70 g Pb(NO3)2 @ 60oC

p er 1 00 g H 2 O unsaturated saturated supersaturated unsaturated

(28)

Describe each situation below. (A) Per 100 g H2O,

100 g NaNO3 @ 50oC.

(B) Cool solution (A) very slowly to 10oC.

(C) Quench solution (A) in an ice bath to 10oC.

unsaturated;

all solute dissolves; clear solution.

supersaturated;

extra solute remains in solution; still clear

saturated; extra solute (20 g)

(29)

How to use a solubility graph?

A. IDENTIFYING A SUBSTANCE ( given

the solubility in g/100 cm3 of water and the temperature)

Look for the intersection of the

solubility and temperature.

(30)

Using Solubility Curves

1) How much KNO3 would dissolve in

100g of water at 50oC?

2) How much NH4Cl would dissolve in

200g of water at 70oC?

3) At what temperature would 22g of

KCl be able to dissolve in 50g of water?

4) Which is more soluble (has a higher

solubility) at 40oC?

 NH3  KClO3

84g 120g

(31)

Learning Check :

What

substance has a solubility of 90 g/100 cm3 in

water at a

temperature of 25ºC ?

(32)
(33)

Learning Check :

What substance has a solubility of 200 g/100 cm3 of water

at a temperature of 90ºC ?

(34)
(35)

Look for the

temperature or solubility

Locate the solubility curve needed and

see for a given temperature, which

solubility it lines up with and visa

versa.

(36)

Learning Check:

What is the solubility of potassium nitrate at 80ºC ?

(37)

• What is the

solubility of potassium nitrate at 80ºC ?

(38)

Learning Check :

At what

temperature will sodium

nitrate have a solubility of 95 g/100 cm3 ?

(39)

Learning Check:

At what

temperature will sodium

nitrate have a solubility of 95 g/100 cm3 ?

(40)

Learning Check:

At what

temperature will potassium iodide have a solubility of

230 g/100 cm3 ?

(41)

Learning Check:

At what

temperature will potassium iodide have a solubility of 130 g/100 cm3 ?

(42)

Using Solubility Curves:

What is the solubility of

sodium chloride at 25ºC in 100 cm3

of water ?

From the solubility graph we see that sodium chlorides solubility is 36 g.

(43)

SOLUBLE OR INSOLUBLE?

Soluble

:

able to be dissolved

Insoluble:

does not dissolve in solution (or

water)

Precipitate:

an insoluble solid formed when two

(44)

To read the

graph:

1. Find the line for the substance. 2. The

amount that dissolves at a given temp. is on the y-axis

.

(45)

How much KNO3

dissolves in 100g H2O at 50oC?

1. Find the line (red)

2. Find the temperature

and follow up to the line. (green)

3. Read across to the

y-axis and this is the answer. (blue)

4. Since it is above the

½-way between 80 and 90, 87g KNO3 will dissolve.

(46)

Unsaturated

supersaturated

Sa

tur

(47)

Types of Solutions:

Saturated solution: point on the line

Contains maximum amount of solute at given tempContains what it should hold

Supersaturated: above the line

Contains more solute than a saturated solutionContains more than it should hold

Unsaturated: below the line is

Contains less solute than saturated solutionContains less solute than it could hold

(48)

.

SOLUBILITY GRAPHS

C o nc e nt ra tio n (g /1 00 g w at e r) temperature 140 120 100 80 60 40 20

10 20 30 40 50 60 70 80

NaNO3

KBr

NH4Cl

KNO3

Na2SO3

(49)

To do Calculations:

 To calculate how much extra has been dissolved:

Extra = Dissolved amt - saturated

in soln (given value) line value @ that temp.

 To calculate how much more can be dissolved:

? Much more = saturated - given value line value @ that temp

(50)

Example 1:

 How much less KCl is dissolved at 20oC than at 60oC in 100g H

2O?

 Read the line value:

32g at 20oC

 Subtract it from the

given value:

(51)

Example 2:

 How much more KCl is required to

saturate the solution if 25g are dissolved

at 40oC?

 Read the line value:

40g

 Subtract the given

value:

(52)

Your turn! Use your graph

1. How much NaCl will dissolve in 100g H2O

at 35oC?

2. How much NH4Cl will dissolve at 50oC? 3. What is the solubility of SO2 at 25oC? 4. What is the solubility of potassium

chlorate in 100 grams of water at 35oC?

5. What is the solubility of potassium

(53)

6. What minimum temperature needed to dissolve 80 grams of sodium nitrate in 100 grams of

water?

7. What minimum temperature needed to dissolve 42 grams of potassium chloride in 100 grams of water?

8. What minimum temperature needed to dissolve 20 grams of KClO3 in 100 grams of water?

9. If 95 grams of potassium nitrate are mixed with 100 grams of water at 45ºC, how much will not

dissolve?

10. If 85 grams of potassium iodide are mixed with 100 grams of water at 0ºC, how much more must

(54)

11. If 55 grams of potassium chlorate are

mixed with 100 grams of water at 55ºC, how much will not dissolve?

12. If 125 grams of potassium iodide are

mixed with 100 grams of water at 10ºC, how much more must be added to

saturate the solution?

13. What is the solubility of potassium

(55)

14. What is the solubility of potassium chlorate in 100

grams of water at 35 oC?

15. What is the solubility of potassium iodide in 100

grams of water at 10 oC?

16. What is the minimum temperature needed to dissolve

80 grams of sodium nitrate in 100 grams of water?

17. What is the minimum temperature needed to dissolve

42 grams of potassium chloride in 100 grams of water?

18. What is the minimum temperature needed to dissolve

(56)

19. If 95 grams of potassium nitrate are mixed with 100

grams of water at 45 oC, how much will not dissolve?

20. If 55 grams of potassium chlorate are mixed with 100

grams of water at 55 oC, how much will not dissolve?

21. If 125 grams of potassium iodide are mixed with 100

grams of water at 10 oC, how much more must be added to saturate the solution?

22. If 85 grams of potassium iodide are mixed with 100

grams of water at 0 oC, how much more must be added to saturate the solution?

23. What is the solubility of potassium chlorate in 50

(57)

 1. 35g NaCl  2. 50g NH4Cl  3. 8g SO2

 4. 13g KClO3  5. 135g KI

 6. 12 C  7. 50 C  8. 45 C

 9. 80g KNO3 a 45 C; 95g KNO3 – 80gKNO3  = 10g KNO3

 10. 125g KI a 0 C; 125g KI – 85 g KNO3  = 40g KNO3

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