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Conceptual

Physical

Science6th Edition

Chapter 16:16.1-16.5

MIXTURES

The Chemist’s Classification of Matter

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homogeneous and heterogeneous mixtures

Homogeneous Heterogeneous

Solutions

Solutions

What is a Solution?• Solution – homogeneous mixture

▪ Solvent – substance present in largest amount

▪ Solutes – other substances in the solution

▪ Aqueous solution – solution with water as the solvent

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Miscible and Immiscible• Two liquids that

completely dissolve in each other are miscibleliquids.

• Two liquids that are not miscible in each other are immiscible liquids.

• Polar water and nonpolar oil are immiscible liquids and do not mix to form a solution.

Like Dissolves Like Rule• Polar solvents dissolve in one another.

• Nonpolar solvents dissolve in one another.

• This is the like dissolves like rule.

• Methanol dissolves in water, but hexane does not dissolve in water.

• Hexane dissolves in benzene, but water does not dissolve in benzene.

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Polar and Nonpolar Solvents• A liquid composed of polar molecules is a polar solvent. Water is a polar solvent.

• A liquid composed of nonpolar molecules is a nonpolar solvent. Hexane is a nonpolar solvent.

Solutions

• Concentration: A measure of the amount of solute dissolved in solution.

Concentration =

Solute

Solution

Grams, molecules, moles

Volume (L, cm3)

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Solutions• Concentration: A measure of the amount

of solute dissolved in solution.

Concentration =Solute

Solution

“concentrated”

Concentration =Solute

“dilute”Solution

Saturated Solutions• A solution that contains less

than the maximum amount of solute is an unsaturated solution or dilute solution.

• A solution containing the maximum amount of solute at a given temperature is a saturated solution.

unsaturated

saturated

ppt

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Solutions• Concentration: A measure of the amount of solute dissolved

in solution.

• Mole: A super-large number, 6.02 1023, used to measure numbers of atoms or molecules, a.k.a. Avogadro’s number.

The formula mass of a

substance expressed in

grams contains one mole.

Example:

C has an atomic mass of 12 amu or 12g/mol

Atomic mass = molar mass and for

compounds, formula mass

• mole

– 602200000000000000000000 things

– 6.02x1023 things

– JUST A NUMBER!!! Like a dozen is 12 things

Molar Mass• The atomic mass of any substance expressed in grams is

the molar mass (MM) of that substance.

• The atomic mass of carbon is 12.01 amu.

• Therefore, the molar mass of carbon is 12.01 g/mol.

• The molar mass of N2 14g/mo/ = 14g/mol 28 g/mol

What is the molar mass of copper(II) nitrite, Cu(NO2)2?

The sum of the atomic masses is as follows:

63.55 + 2(14.01 + 16.00 + 16.00) =

63.55 + 2(46.01) = 155.57 amu

The molar mass for Cu(NO2)2 is 155.57 g/mol

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Formula (molar) Mass

Substance Formula Mass (g/mol)

Carbon, C 12

Oxygen, O2 32

Carbon dioxide, CO2 44

Sucrose, C12H22O11 342

Water, H2O, has a formula mass of 18g/mol. How many moles of water are there in 9 grams of water?

A. 0.5 moles

B. 2 mole

C. 288 moles

D. 8 moles

Solutions

CHECK YOUR NEIGHBOR

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How many grams of water, H2O, are there in 2 moles of water?

A. 1 gram

B. 9 grams

C. 18 grams

D. 36 grams

Solutions

CHECK YOUR ANSWER

Water, H2O, has a formula mass of 18g/mol.

How many moles of water are there in 9 grams of water?

How many water molecules are there?

How many H atoms?

Solutions

CHECK YOUR NEIGHBOR

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Solutions

Sucrose, C12H22O11 = 342 g/mole

Solutions

Molarity = moles of solute Liters of solution

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Solutions

Molarity = moles of solute Liters of solution

• Molarity: A unit of concentration expressed in moles solute per liter of solution.

Units: Moles/L or M

Solution A is 1 moles/L and Solution B is 4 moles/Lor

Solution A is 1 M and Solution B is 4 MSolution A is 1 molar ad solution B is 4 molar

Solutions

• Molarity: A unit of concentration expressed in moles solute per liter of solution.

• ppm: A unit of concentration expressed in milligrams solute in liters of solution.

1 ppm =

1 part solute

1,000,000 parts solution

1 milligram solute

1 liter solution=

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Solubility• Solubility: The ability of a solute to

dissolve in a solvent.

• Soluble: Said of a solute that has appreciable solubility.

Soaps and Detergents

• Soaps and detergents have both polar and nonpolar parts.

• Nonpolar part attracts to the “grime”.

• Polar part attracts to water.

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How Substances Dissolve

“—like dissolves like—”

Polar + PolarNonpolar + nonpolar

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Interpreting a Chemical Equation

• Let’s look at the reaction of nitrogen monoxide with oxygen to produce nitrogen dioxide:

2 NO(g) + 1 O2(g) → 2 NO2(g)

• Two molecules of NO gas react with one molecule of O2 gas to produce two molecules of NO2 gas.

2 NO(g) + 1 O2(g) → 2 NO2(g)

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Mole Ratios

2 NO(g) + O2(g) → 2 NO2(g)

• We can now read the above, balanced chemical equation as “2 moles of NO gas react with 1 mole of O2 gas to produce 2 moles of NO2 gas.”

• The coefficients indicate the ratio of moles, or mole ratio, of reactants and products in every balanced chemical equation.

Moles and Equation Coefficients

NO(g) O2(g) → NO2(g)

2 molecules 1 molecule 2 molecules

2 moles 1 mole 2 moles

• Coefficients represent molecules, so we can multiply each of the coefficients and look at more than the individual molecules.

2 NO(g) + 1O2(g) → 2 NO2(g)

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Interpretation of Coefficients• From a balanced chemical equation, we know

how many molecules or moles of a substance react and how many moles of product(s) are produced.

Mole–Mole Relationships• We can use a balanced chemical equation to

write mole ratio, which can be used as unit factors.

N2(g) + O2(g) → NO(g)

• Since 1 mol of N2 reacts with 1 mol of O2 to produce 2 mol of NO, we can write the following mole relationships:

1 mol N2

1 mol O2

1 mol N2

2 mol NO

1 mol O2

2 mol NO

1 mol O2

1 mol N2

2 mol NO

1 mol N2

2 mol NO

1 mol O2

1 1 2

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Ex: Mole–Mole Calculations

• How many moles of oxygen react with 2.25 mols of nitrogen?

N2(g) + O2(g) → 2 NO(g)

• We want mols O2; we have 2.25 mols N2.

• Use 1 mol N2 = 1 mol O2

Mole–Mole Problems, Continued

• How many moles of oxygen react with 37.5 moles of sulfur dioxide in the production of sulfur trioxide gas?

2 SO2(g) + O2(g) → 2 SO3(g)

• From the balanced equation, 1 mol of oxygen reacts with 2 mol sulfur dioxide.

1 mol of O2 : 2 mols of SO2

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Mole–Mole Problems, Continued

2 SO2(g) + O2(g) → 2 SO3(g)

How many mols of SO3 are produced?

Balancing Reactions

1. Balance the elements one at a time using coefficients. A coefficient is a small WHOLE number that is written in front

of a chemical formula in a chemical equation.

When no coefficient is written, the coefficient is assumed to be 1.

It is best to begin with elements OTHER THAN hydrogen and

oxygen. These elements often occur more than twice in

equations.

** You must NOT attempt to balance the equation by changing

subscripts in chemical formulas!!!!!!

2. Check each atom to be sure that the equation is correctly balanced.

3. Finally, make sure that all of the coefficients are in the LOWEST

possible whole number ratios. (At least one of the coefficients

must be a prime number!)

2 SO2(g) + O2(g) → 2 SO3(g)

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Your turn ::: mol-mol problem

How many moles of oxygen gas reacts with 30.0

mols of sulfur dioxide gas?

SO2(g) + O2(g) → SO3(g)

Is this equation balanced?

15.Omols

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