chapter 2 matter and atoms 2.3 mixtures and solutions

CHAPTER 2

Matter and Atoms

2.3 Mixtures and Solutions

2 2.3 Mixtures and Solutions

A recipe calls for you to “mix until homogeneous.”

What does that mean?

3 2.3 Mixtures and Solutions

A mixture that is uniform throughout.

4 2.3 Mixtures and Solutions

A mixture that is uniform throughout. Different samples may have different compositions.

5 2.3 Mixtures and Solutions

6 2.3 Mixtures and Solutions

What happens when sugar is added to water?

7 2.3 Mixtures and Solutions

What happens when sugar is added to water?

A solution is obtained.

8 2.3 Mixtures and Solutions

Is orange juice a solution?

Hint: Are things dissolved in orange juice?

9 2.3 Mixtures and Solutions

Is orange juice a solution?

It is partially a solution because some chemicals are

dissolved in water, but some bits (like pulp) are not.

10 2.3 Mixtures and Solutions

These four solutions contain the same solvent and solute.

Which one is the most concentrated solution?Which one is the most dilute solution?

11 2.3 Mixtures and Solutions

concentration: the amount of each solute compared to the total solution.

12 2.3 Mixtures and Solutions

• Can you dissolve salt in water?

Variables

Amount of saltAmount of water

13 2.3 Mixtures and Solutions

• Can you dissolve salt in water?

• Can you continue adding more and more salt, and still get a solution?

Variables

Amount of saltAmount of water

14 2.3 Mixtures and Solutions

• Can you dissolve salt in water?

• Can you continue adding more and more salt, and still get a solution?

• Can you dissolve more salt when you increase the temperature?

Variables

Amount of saltAmount of water

Amount of saltAmount of waterTemperature

15 2.3 Mixtures and Solutions

solubility: the amount of a solute that will dissolve in a particular solvent at a particular temperature and pressure.

Solubility of common substances in water at 25oC

16 2.3 Mixtures and Solutions

If the concentration of a sugar solution is 75 g/L, how much solution do you need if you want 10 g of sugar?

17 2.3 Mixtures and Solutions

If the concentration of a sugar solution is 75 g/L, how much solution do you need if you want 10 g of sugar?

Asked: Volume of solution

Given: 10 g of solute and concentration of 75 g/L

Relationships:mass of solute

Liters of solutionconcentration in g L

18 2.3 Mixtures and Solutions

If the concentration of a sugar solution is 75 g/L, how much solution do you need if you want 10 g of sugar?

Asked: Volume of solution

Given: 10 g of solute and concentration of 75 g/L

Relationships:

Solve:

mass of soluteLiters of solution

concentration in g L

100.1 13333

75

gL or

gL

Lm

19 2.3 Mixtures and Solutions

How much menthol do you need to make 10 kg of mouthwash if the concentration of menthol must be 0.05%?

20 2.3 Mixtures and Solutions

How much menthol do you need to make 10 kg of mouthwash if the concentration of menthol must be 0.05%?

Asked: Mass of solute

Given: 10 kg of solution, solute concentration of 0.05%

Relationships: %

100

concentration inmass of solute mass of solution

21 2.3 Mixtures and Solutions

How much menthol do you need to make 10 kg of mouthwash if the concentration of menthol must be 0.05%?

Asked: Mass of solute

Given: 10 kg of solution, solute concentration of 0.05%

Relationships:

Solve:

%

100

concentration inmass of solute mass of solution

0.05%10 0.005

105

0kg kg or g

22 2.3 Mixtures and Solutions

molarity: the number of moles of solute per liter of solution.

( )

( )

amount of solute moles molesmolarity

volume of solvent liters L

molesM

L

23 2.3 Mixtures and Solutions

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

24 2.3 Mixtures and Solutions

Asked: The molarity of a solution

Given: The amount of solute (citric acid) and the volume of solution

Relationships:

moles solutemolarity

volume of solution L

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

25 2.3 Mixtures and Solutions

Asked: The molarity of a solution

Given: The amount of solute (citric acid) and the volume of solution

Relationships:

Solve: Start by calculating the formula mass of C6H8O7:

moles solute

molarityvolume of solution L

6 12.011 8 1.0079 7 1 192.5. 12999 g mole

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

26 2.3 Mixtures and Solutions

Asked: The molarity of a solution

Given: The amount of solute (citric acid) and the volume of solution

Relationships:

Solve: Start by calculating the formula mass of C6H8O7:

Next we calculate the number of moles in 10.0 g of C6H8O7:

moles solute

molarityvolume of solution L

6 12.011 8 1.0079 7 15.999 192.12 g mole

1# 10.0

192.120.0521

molemoles g

gmoles

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

27 2.3 Mixtures and Solutions

If 10.0 g of citric acid (C6H8O7) is added to 500 mL of water, what is the molarity of the resulting solution?

Asked: The molarity of a solution

Given: The amount of solute (citric acid) and the volume of solution

Relationships:

Solve: Start by calculating the formula mass of C6H8O7:

Next we calculate the number of moles in 10.0 g of C6H8O7:

Answer:

moles solute

molarityvolume of solution L

6 12.011 8 1.0079 7 15.999 192.12 g mole

1# 10.0 0.0521

192.12

molemoles g moles

g

0.0521

0.5000.104

molesmolarity

LM

28 2.3 Mixtures and Solutions

Ascorbic acid = Vitamin C

Vitamin C acts as a food preservative by reacting with oxygen (O2)

Ascorbic acid

C6H8O6

29 2.3 Mixtures and Solutions

30 2.3 Mixtures and Solutions

How much (volume) of a 1 M ascorbic acid solution will completely react with 0.02 moles of oxygen (O2)?

31 2.3 Mixtures and Solutions

Asked: Volume of solution

Given: Concentration (1M) and balanced reaction

Relationships:

According to the balanced reaction we need 2 moles of ascorbic acid for every mole of O2.

moles solute

molarityvolume of solution L

How much (volume) of a 1 M ascorbic acid solution will completely react with 0.02 moles of oxygen (O2)?

32 2.3 Mixtures and Solutions

Asked: Volume of solution

Given: Concentration (1M) and balanced reaction

Relationships:

According to the balanced reaction we need 2 moles of ascorbic acid for every mole of O2.

Solve: That means we need 0.04 moles of ascorbic acid:

0.040 4

10.04

moles solute molesvolume L L or

molaritL

Mm

y

moles solute

molarityvolume of solution L

How much (volume) of a 1 M ascorbic acid solution will completely react with 0.02 moles of oxygen (O2)?

33 2.3 Mixtures and Solutions

Asked: Volume of solution

Given: Concentration (1M) and balanced reaction

Relationships:

According to the balanced reaction we need 2 moles of ascorbic acid for every mole of O2.

Solve: That means we need 0.04 moles of ascorbic acid:

Answer: 40 mL of the solution contains 0.04 moles of ascorbic acid, which is enough to react with 0.02 moles of oxygen (O2).

0.040 4

10.04

moles solute molesvolume L L or

molaritL

Mm

y

moles solute

molarityvolume of solution L

How much (volume) of a 1 M ascorbic acid solution will completely react with 0.02 moles of oxygen (O2)?

34 2.3 Mixtures and Solutions

The air you breathe is a mixture!

35 2.3 Mixtures and Solutions

Air takes up less space under high pressure.

36 2.3 Mixtures and Solutions

Standard

Temperature and

Pressure

molar volume: the amount of space occupied by a mole of gas at STP. It is equal to 22.4 L.

0oC

1 atm

37 2.3 Mixtures and Solutions

Partial pressures

The total pressure in a mixture of gases is the

sum of the partial pressures

of each individual gas in the mixture.

38 2.3 Mixtures and Solutions

Gas A

Gas BGas C

Gas A Gas B

Gas CTotal pressure

=

+

+

Partial pressure of A

Partial pressure of C

Partial pressure of B

Partial pressures

39 2.3 Mixtures and Solutions

If 1 L of helium (75%) and neon (25%) is at STP, what is the partial pressure of helium?

40 2.3 Mixtures and Solutions

Asked: Partial pressure of helium

Given: 75% He and 25% Ne at STP conditionsStandard pressure is 101,325 Pa or 1 atm

Relationships: The total pressure is the sum of the partial pressures of each gas.

If 1 L of helium (75%) and neon (25%) is at STP, what is the partial pressure of helium?

41 2.3 Mixtures and Solutions

Asked: Partial pressure of helium

Given: 75% He and 25% Ne at STP conditionsStandard pressure is 101,325 Pa or 1 atm

Relationships: The total pressure is the sum of the partial pressures of each gas.

Solve: 75,9940.75 101,3

0.75

25

0.75 1

Pa

or

Pa

atmatm

or

If 1 L of helium (75%) and neon (25%) is at STP, what is the partial pressure of helium?

42 2.3 Mixtures and Solutions

Asked: Partial pressure of helium

Given: 75% He and 25% Ne at STP conditionsStandard pressure is 101,325 Pa or 1 atm

Relationships: The total pressure is the sum of the partial pressures of each gas.

Solve:

Answer: The partial pressure of helium is 75,994 Pa or 0.75 atm.

75,9940.75 101,3

0.75

25

0.75 1

Pa

or

Pa

atmatm

or

If 1 L of helium (75%) and neon (25%) is at STP, what is the partial pressure of helium?

43 2.3 Mixtures and Solutions

STP conditions:

Standard

Temperature (0oC)

Pressure (1 atm)

Air is a mixture of gases. Based on Dalton’s law of partial pressures:

2 2...air N O ArP P P P

Concentration of a solution can be expressed in:

mass per volume

mass percent

molarity moles of solute

molarity Mliters of solvent