Introduction to solutions
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Introduction to Solutions. MIXTURE. PURE SUBSTANCE. yes. no. yes. no. Is the composition uniform?. Can it be chemically decomposed?. Colloids. Suspensions. Matter Flowchart. MATTER. yes. no. Can it be physically separated?. Homogeneous Mixture (solution). Heterogeneous Mixture.

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Introduction to Solutions

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Introduction to solutions

Introduction to Solutions


Matter flowchart

MIXTURE

PURE SUBSTANCE

yes

no

yes

no

Is the composition uniform?

Can it be chemically decomposed?

Colloids

Suspensions

Matter Flowchart

MATTER

yes

no

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture

Compound

Element


Pure substances

Pure Substances

  • A pure substance has a definite composition.

  • Pure substances can be

    elements or compounds


Mixtures

Mixtures

  • A mixture can be either homogeneous or heterogeneous.

  • A homogeneous mixture is one in which all of the components are UNIFORMILY distributed.

    • Ex: chocolate milk

  • A heterogeneous mixture is one in which the components are NOT UNIFORMILY distributed.

    • Ex: pizza

HOMOGENEOUS

HETEROGENEOUS


Solutions

Solutions

Solutions, in chemistry, are homogeneous mixtures of two or more substances.

The substance present in largest quantity usually is called the solvent. The solvent can be either a liquid or a solid.

The substance that is present in smallest quantity is said to be dissolved and is called the solute. The solute can be either a gas, a liquid, or a solid.


Concept check

Concept Check

Coke lists as its ingredients as: “carbonated water, high fructose corn syrup and/or sucrose, caramel color, phosphoric acid, natural flavors, caffeine”.

What is the solvent?

What are the solutes?

What can we classify CO2 as in carbonated beverages?


Introduction to solutions

  • Miscible liquids can easily dissolve in one another.

  • Immiscible liquids are not soluble in each other.

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Heterogeneous mixtures

Heterogeneous Mixtures

  • Suspensions-a heterogeneous mixture that contains large particles that “settle out” unless constantly stirred or agitated

    • Ex: freshly squeezed OJ, salad dressing

  • Colloids-a heterogeneous mixture in which the components are microscopic and will not separate when left standing.

    • Ex: mayonnaise, milk, stick deodorant


How does a solid dissolve into a liquid

How does a solid dissolve into a liquid?

  • Solvent molecules are attracted to surface ions.

  • Each ion is surrounded by solvent molecules.

Ionic solid dissolving in water


Dissolution vs reaction

dry

Dissolution vs. Reaction

  • Dissolution is a physical change—you can get back the original solute by evaporating the solvent.

  • If you cant, the substance didn’t dissolve, it reacted.

Ni(s) + HCl(aq)

NiCl2(aq) + H2(g)

NiCl2(s)


Factors affecting solubility

Factors Affecting Solubility

  • Chemists use the saying “like dissolves like:”

    • Polar substances tend to dissolve in polar solvents.

    • Nonpolar substances tend to dissolve in nonpolar solvents.

Oil is nonpolar while water is polar.

They are immiscible.


Saturation types

Saturation Types

  • Saturated

  • Unsaturated


Degree of saturation

Degree of saturation

  • Unsaturated Solution

    • Less than the maximum amount of solute for that temperature is dissolved in the solvent.

    • No solid remains in flask.


Degree of saturation1

Degree of saturation

  • Saturated solution

    • Solvent holds as much solute as is possible at that temperature.

    • Undissolved solid remains in flask.

    • Dissolved solute is in dynamic equilibrium with solid solute particles.


Saturated solution

Saturated Solution

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Degree of saturation2

Degree of saturation

  • Supersaturated Solution

    • Solvent holds more solute than is normally possible at that temperature.

    • These solutions are unstable


Temperature and solubility

Temperature and Solubility

Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.


Solubility

Solubility

What amount of CaCl2 can be dissolved in 100 g H2O at 20° C?

ANSWER: 75 g CaCl2


Let s play a quick game of

Let’s play a quick game of….

Saturated or Unsaturated?

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Saturated or unsaturated

Saturated or Unsaturated?

  • a solution that contains 70g of NaNO3 at 30°C

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Unsaturated

Unsaturated!

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Saturated or unsaturated1

Saturated or Unsaturated?

  • a solution that contains 50g of NH4Cl at 50°C

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Saturated

saturated!

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Saturated or unsaturated2

Saturated or Unsaturated?

  • a solution that contains 20g of KClO3 at 50°C

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Saturated1

saturated!

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Saturated or unsaturated3

Saturated or Unsaturated?

  • a solution that contains 70g of KI at 0°C

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Unsaturated1

Unsaturated!

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Saturated or unsaturated4

Saturated or Unsaturated?

  • A mass of 100 g of NaNO3 is dissolved in 100 g of water at 80ºC

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Unsaturated2

Unsaturated!

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The end

THE END

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Solubility of gases

Solubility of Gases

  • In general, the solubility of gases in water increases with increasing mass.

    Why?

  • Larger molecules have stronger dispersion forces.

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Gases in solution

Gases in Solution

  • The solubility of liquids and solids does not change appreciably with pressure.

  • But, the solubility of a gas in a liquid is directly proportional to its pressure.

Increasing pressure above solution forces more gas to dissolve.

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Temperature

Temperature

  • The opposite is true of gases. Higher temperature drives gases out of solution.

    • Carbonated soft drinks are more “bubbly” if stored in the refrigerator.

    • Warm lakes have less O2 dissolved in them than cool lakes.

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Introduction to solutions

solubility increases with increasing temperature

solubility decreases with increasing temperature

Temperature and Solubility

Solid solubility and temperature

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Introduction to solutions

Temperature and Solubility

Gas solubility and temperature

solubility usually decreases with increasing temperature

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Electrolytes

Electrolytes

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Electrolyte

Electrolyte

Electrolyte: a substance that dissolves in water to give a solution that conducts electric current

  • Any soluble ionic compound is an electrolyte

  • Strong acids are electrolytes

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